First impressions

Cool to touch (and to look at, especially when compared to some of the items in the range), the Skien Valley Hoodie from Columbia is a lightweight, long-sleeved top that can be worn as a base layer beneath a fleece jacket or waterproof shells while hiking, or as a stand-alone top during dry and warm weather, especially when biting bugs are making a nuisance of themselves.

When I received several items from Columbia’s new Insect Shield collection to test, this was the first garment I reached for when hiking and camping on sweaty summer evenings, because it felt nice, looked decent and seemed like a good first line of defense against the blood-sucking beasts that make a habit of attacking me. Here’s how it performed.

Design and Materials

The Skien Valley hoodie is made with a material mixture of polyester and elastane. Oddly, Columbia don’t specify whether the polyester used in this top is recycled, whereas the same fabric used in other garments in the collection is recycled (in the absence of clear labelling, we’re going to assume that it isn’t recycled in this case). The elastane content in the top makes it nice and stretchy.

Available for both men and women (and also in a ‘Big’ version), this top has a relaxed, baggy look and feel. There are no pockets, but it has a hood, obviously (clue in the name) and substantial thumb hoops to keep the long sleeves in place when you add another layer over the top (and also to help protect wrists from biting bugs).

This top is part of Columbia’s new Insect Shield collection of outdoor apparel, all treated with a long-lasting chemical called permethrin, which is capable of deterring, stunning or even killing bugs that come into contact with it. Like the rest of the range, the hoodie is also light colored, because pests like mosquitoes are – apparently – less attracted to more neutral hues.

On the trails

I have been testing the Skien Valley hoodie over the scorching summer we have just enjoyed/endured (I liked it, but so did the bugs – so no better time to put this stuff to the test). This season I have mostly been hiking and camping on Dartmoor and in the Wicklow Mountains, both places I’m more accustomed to experiencing in the drizzle, but not in 2025.

We’ve had no less than four heatwaves over the last four months, and the midges (no-see-ums) have been out in force during still evenings on the trail, in camp and around crags. When this happens, you can either cover every inch of yourself in lightweight clothing, from base layers to long socks, or douse yourself in insect repellent – or take a belt and braces approach, and do a mixture of both.

Alternatively, you can clad yourself in clobber from Columbia’s Insect Shield-infused Skien Valley range, which is a bit like doing both. This is the approach I took in the Wicklow Mountains, where the midges were particularly horrendous. More so than the Skien Valley shirt (which I liked, but for other reasons) this hoodie proved to be particularly effective as armor against biting bugs, because it covered my whole top half, including my neck and – thanks to the thumb hoops – protected my wrists (always a target for midges and mosquitoes).

Also, even when paired with the similarly light-colored Skien Valley cargo pants, it looks decent, so when I was hanging out in communal campsites rather than wild camping on my own, I didn’t feel like a complete plum, as I did while wearing the Booney Hat, which is also part of the range.

Obviously it doesn’t protect your face from the irritating little monsters, so when they were at their worst I did often resort to wearing the wide brimmed hat with its full-face net, or when the temperatures cooled a little, pulling on the Skien Valley Hooded Light Jacket, which also features face netting.

During the day, I found the Skien Valley hoodie to be a very comfortable top to hike in, especially on hot days when I was exploring the exposed tor tops and mountain sides, where it provided excellent protection from the sun and the loose-fit style allowed lots of airflow. And, during climbing and scrambling adventures, the top boasts plenty of stretch, so you have a full range of movement and can reach for hand holds.

All-round, it’s a fine, functional piece of kit, and the item I’m likely to get the most use out of from the whole Skien Valley range.

Founded in the Swedish ski resort of Åre in 1986, Peak Performance was launched by a pair of passionate skiers on a mission to create 'garments that combined excellent functionality with simple, attractive design'. Fast forward to today and the brand still sells popular skiing gear, as well as hiking, trail running and mountain biking apparel, and even gym and golf wear.

Finnish multinational Amer Sports bought the brand in 2018 and today it sits in its roster alongside the likes of Arc’teryx and Salomon. As with Arc’teryx, you can expect to pay a pretty penny for Peak Performance’s expertly and sustainably crafted premium gear. I recently tested the brand’s minimalist Elevate Hood Jacket and was impressed with both its performance and its innovative recyclable design.

I was stoked to test its Freelight Crew, a lightweight fleece mid-layer. It's available in both men’s and women’s versions and features the same Polartec Power Grid insulation as Berghaus’ MTN Guide MW Hoody. I was intrigued to see how it would compare on the trails.

First impressions

Peak Performance’s Freelight range is a collection of garments designed with a focus on being lightweight, windproof, water repellent and packable. It’s not the only Swedish brand focussing on this kind of gear: garments in Haglöfs’ L.I.M (Less Is More) range are designed with similar qualities in mind. As someone who enjoys going fast and light wherever possible, I’m always up for giving this kind of gear a go.

The Freelight Crew is sold as a mid-layer but, thanks to its low weight, feels like a long-sleeved t-shirt. It’s an attractive garment with its bold chest pocket patch and minimalist look. Fit wise, it’s relatively relaxed so if you’re someone who prefers an athletic fit, perhaps try the size down.

Look closely and the texture of its fleece arrays are obvious. Turning the top inside out reveals its army of neatly aligned fleece clusters. The ratio of fleece to space here is lower than with the tightly-packed arrays seen on Berghaus’ MTN Guide MW Hoody, pointing to a cooler, more breathable mid-layer. Nevertheless, when I put it on, its insulating abilities were immediately apparent. Let’s take a closer look at the ideas behind Polartec's Power Grid design...

Polartec Power Grid

For the uninitiated, Polartec is the brand that invented synthetic fleece back in 1979, patented as Polartec Polarfleece. These days brand is almost as ubiquitous in outdoor clothing, particularly mid-layers, as Vibram is in footwear and Gore-Tex is in waterproof jackets.

The Power Grid fabric is intended for lightweight garments designed with freedom of movement and breathability in mind. The grid in the name refers to the fact that, rather than a solid layer of insulating material, it features interspersed fleece clusters arranged consistently in a grid structure. While the clusters perform their heat holding magic, the space between them wicks moisture away, creating a breathable fabric that works with the body to regulate your temperature.

This quality is the Holy Grail of any mid-layer and we’ve highly rated several Power Grid garments in recent years, such as North Face’s Stormgap and Bolt jackets. Another notable benefit of the grid design is that it’s more compressible than a standard fleece, making it easier to stuff into a small space in a daypack.

Not all Power Grid fabrics are created equally and it’s up to the brands who create these mid-layers to decide on the fleece-to-space ratio. In the lightweight Freelight Crew, there’s more space than there is fleece, with a gsm (grams per square meter) of 119. The top's outer fabric is a 90D poplin that’s nicely stretchy for unrestricted movement.

Peak Performance has committed to removing intentional use of PFAS (per- and polyfluoroalkyl substances) by 2025 and the Freelight is, unsurprisingly, free of them. Numerous health concerns have been raised against these chemicals and many brands are doing their utmost to remove them.

Other features

The Freelight Crew’s feature set is fairly minimal, a quality that’s true of many of Peak Performance’s gear. The standout feature is its zippered chest pocket and logo panel, partly because it’s a different color to the rest of the top (unless you get the Black version) but mostly because it really is the only obvious feature.

The compartment is large enough for a phone and the zipper features a handy pull. To be honest, I didn’t get a great deal of use out it as this lightweight pouch isn't the most comfortable place to store any items of significant weight – even a headlamp feels clunky in there. However, it’s a decent place to stash a baseplate compass, or store a bank card or ski pass. It's a little bit style over substance, I feel.

The hem and and cuffs are noticeably elasticated. However, I found that they were already pretty loose anyway, almost negating the point of having elastic in the first place. In terms of holding on to heat, I feel these would have been better if they were tighter, with the elastic then giving the flexibility to expand them if necessary.

The top’s flatlock seams are designed to reduce dreaded chaffing and there are no seams across the shoulders, making the top more comfortable to wear with a backpack.

In the field

I’ve been testing the Freelight Crew throughout the summer, wearing it on hiking trips to Wales’ Bannau Brycheiniog National Park, as well as for walks in Pembrokeshire National Park and South West England. I’ve worn it both as a mid-layer in the evenings and as a base layer on warmer days.

I found that it was comfortable when worn as both, though the bobbly texture of its fleece grid takes a bit of getting used to when worn as a base layer. It was interesting swapping between a standard technical t-shirt (I did this little experiment with the Montane Dart) and the Freelight Crew while simply sat down on a hot day. The difference in warmth is immediately obvious, underlining the effectiveness of Polartec’s insulation and the Freelight’s really impressive warmth-to-weight ratio.

A benefit of the Freelight’s synthetic fabrics is that they’re quick drying. It was never that long after working up a sweat or after a burst of light rain that the top would be pretty much dry once more. Plus, the Power Grid fabric maintains its insulating qualities over time, even after many, many wash cycles, making the top a durable option for years of wear.

My main qualms with the Freelight Crew, especially when used as a technical mid-layer for more serious outdoor adventures, are its relaxed fit and lack of front zip. Its baggy fit isn’t ideal when adding other layers over the top, as I’d get little rolls of fabric that I’d have to straighten out. The loose sleeves were particularly problematic and would often ride up when adding other layers. From a purely aesthetic point of view, I personally prefer an athletic fit too.

No front zip means no ability to dump heat during a sustained ascent or during an involved summer scramble. As established, the Power Grid fleece holds heat readily and, although the top is very breathable, it’s still nice to be able to go for the nuclear option of opening everything up once in a while.

These issues aside, it's still a high quality top that delivers superb warmth-to-weight. It's great for summer hiking missions where you might need a quick extra layer for the summits or ridges thanks to its lightweight packability. It's also a good looking top for everyday wear.

Also consider

Comparison table

Want to get outdoors and enjoy the trail this autumn? You might need to invest in some new gear.

Along with a decent raincoat and a reliable pair of hiking pants, a good fleece layer is key for cold and breezy weather, providing some much-needed insulation when the temperature drops without the bulk of a down jacket. One of our favorite models does just that, and is now 30% in time for autumn!

The men's Patagonia Better Sweater 1/4 zip fleece is a trusty option for cold and windy days in the wilderness, and it's now available for just $96.93 at REI.

This cozy jacket is made from 100% recycled polyester, which wraps around your upper half to keep heat from escaping, while its elasticated cuffs and high neck stop the cold from coming in.

Expert tester Craig Taylor wore his Better Sweater for four years before writing his review for Advnture, and had very few complaints.

"As I look at it now, there’s barely a thread out of place, and despite living through dozens of rough adventures, it looks pretty much as it did on the day I bought it," says Craig.

"Thick and comfortable, one of the things I love most about the Patagonia Better Sweater 1/4-Zip Fleece is how comfortable it feels under a heavy pack.

"That’s thanks in a large part to the “bounce” in the material, as well as some clever design features Patagonia have implemented in production."

If you're not in the US, you can look below for today's best Patagonia Better Sweater 1/4 zip fleece deals where you are.

• The best waterproof jackets: brave the elements with these top-rated hard and softshells
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First impressions

Not only is the Skien Valley long-sleeved top a nice-looking hiking shirt (available for men and women), with some great vents and features, it’s also part of Columbia’s new Insect Shield Collection, which – so the US-based brand – can protect you from bity beasts while you’re trying to enjoy alfresco adventures.

Not all insects are annoying, most do a very valuable job, but I think we can all agree that some, like mosquitoes and midges, are the bastard spawn of the devil and, when they’re not actually killing people, they seem to exist only to drive hikers and campers mad and ruin the outdoor experience. There are myriad ways to try and keep them at bay, including using spray-on repellents and creams, from deet to more natural deterrents like citronella and eucalyptus – but this can prove costly, the bottles take up room in your backpack and some have a very strong smell and feel greasy on your skin.

Another option is to cover up as much of your body as possible, with standard base layers and long socks and so on, but that can get very hot and sweaty when you’re hiking and spending time in camp in the summer, which is exactly when such annoying insects come out.

Alternatively, you can try using treated clothing, like garments from Columbia’s new Insect Shield collection. The Skien Valley shirt is part of this range of gnat-smashing wearable gear, all of which are impregnated with an insecticide called permethrin, which the American brand say works against mosquitoes, ticks, ants, flies, chiggers, and no-see-ums. If this stuff works, I’m all over it.

Design and Materials

The pieces of clothing in the Insect Shield Collection, including the Skien Valley shirt, aren’t just treated with permethrin, they are also designed to deter biting insects from landing on you in the first place. This starts with the light colorways used (less attractive to the creatures, apparently) and extends to extra coverage (long sleeves, collar etc) and mesh-backed vents on the back and the elbows, which allow cool air in and hot air to escape, without opening a door of opportunity for the biting insects to get in and have a munch on you.

The nylon material is light, but not so thin that a mosquito can stab its proboscis through it, and the thickness also protects you from the sun (as does the collar). The material contains Omni-Wick technology, which shifts moisture (sweat) away from your body to the outside of the garment, where it quickly evaporates.

Aside from these features, both the men’s and the women’s version of this shirt boast two chest pockets. On the women’s shirt these are both secured with Velcro, but on the men’s shirt the one on the left has a vertical opening and a zip. All versions of the shirt have a secret interior pocket made from mesh, for stashing something like a credit card very discreetly if you’re traveling in places where security is an issue.

The snap closures on the cuff and front of the shirt make it very quick and easy to put on and take off, and to open up when you want extra air flow. The collar can be flipped up to supply extra protection for your neck from the sun.

It’s just a shame that no recycled fabric appears to have been used in the construction of the Skien Valley shirt, and that it doesn't contain any treatment to prevent the build up of bacteria and bad odors over time.

On the trails

I have been wearing the Skien Valley shirt and other elements of Columbia’s Insect Shield Collection during this long hot summer, while hiking and camping in England and Ireland. In one campsite in particular, in the Wicklow Mountains just outside Dublin, during a still day amid a stifling heatwave, the midges were at plague proportions, emerging in aggressive clouds as soon as the sun set, and I was able to give the gear a really good test.

In my experience, after I changed out of standard kit and into the Insect Shield clothing, there was a noticeable difference in the amount of attention I was getting from the biting insects, who presumably went and annoyed someone else (sorry, not sorry, camping comrades).

I can’t say I was completely shielded from bites by this shirt, because it doesn’t offer full coverage (unlike the Skien Valley Hooded Light Jacket, which has a face net and everything), and in the campsite I ended up donning an ensemble that comprised the Skien Valley Hoodie, Cargo Hiking trousers and Booney hat.

But where this shirt comes into its own is during hiking escapades and walking adventures. The vents on the elbows and shoulders are excellent, allowing delicious bursts of breeze to get through and cool your skin, while the mesh backing behind these flaps keeps insects out.

Obviously it’s best to wear the sleeves down when you’re in camp, to fend off squadrons of mosquitoes, but when you’re striding along the trail and breaking a sweat, it’s easy and pleasant to roll the cuffs up and use the snap closures to keep them in place. The same style closures on the front allow you to open the shirt up as much as you like, to let even more air in, while the material supplies excellent protection from the sun.

Although I’m not in the habit of carrying too much in my shirts, the pockets on the Skien Valley top are impressive, especially the zippered on the left, where you can stash cash, cards and other things you really don’t want to lose. I wasn’t too worried about encountering bandits in the Wicklow Mountains, but the secret inner pocket is a nice touch for people traveling in places where pickpocketing might be more of a concern.

Overall, this is a very well-designed, highly functional, impressive featured hiking shirt, that looks decent with hiking pants or shorts when you’re on the trail, and works well with jeans in more social circumstances. It supplies more protection from aggressive and annoying flora and fauna than the vast majority of other tops on the market, and it’s available for a sensible price.

Also consider

First impressions

Helly Hansen is one of the world's oldest and most trusted outdoor brands.

The Norwegian stalwart was founded in 1877 by sea captain Helly Juell Hansen, who wanted a better way to protect himself from the harsh conditions at sea. Tired of toiling in soaking clothes, Hansen and his wife, Margarethe, created innovative waterproof jackets and pants to protect sailors from the wind and waves while they worked.

In the almost 150 years since, Helly Hansen has earned a stellar reputation for creating comfy and reliable outdoor apparel for people preparing to get out and take on the elements, gear such as the new Tech T-shirt 2.0.

This trail-ready top is made from breathable 100%-recycled polyester and is designed for repeated use on the trails. With comfort and moisture control the main priorities, the T features flatlock seams, and the material is moisture-wicking and quickly sheds sweat, so you can trek or run without irritating additional weight or moisture.

This Helly Hansen top, which is available in six different colorways, is bluesign approved, meaning it's been manufactured to the highest possible standards for environmental and worker protection.

Helly Hansen Tech T-shirt 2.0: on the trails

I was lucky enough to snag two Tech 2.0 T-shirts in June, when I joined the AQA hiking charity for their ascent of Ben Nevis, in Scotland.

Following my trip to the Highlands, I've put the Colbalt and Grey Fog colorways to the test over plenty of high-intensity treks and trail runs in the English countryside. I was treated to plenty of varied weather in testing, including several rainy days and a scorching heatwave.

Read on to see how the Helly Hansen Tech 2.0 T-shirt got on in the field.

Fit and comfort

There's little worse than an ill-fitting T-shirt on the trails. Too small and you can feel constrained, but too big and you can feel like you're drowning in excess material.

The Tech 2.0 T-shirt dodges these problems with a comfortable fit that feels snug in all the right places without getting too tight. True to size, it fit nicely around my stomach, chest, and shoulders without constraining my movements.

I'm often irritated by the sleeve lengths of outdoor tops, which can be unfashionably baggy or rise so high up my upper arms that they feel like a vest. The sleeves on the Tech 2.0 T-shirt strike a happy medium, falling a couple of inches above my elbow and exposing a little upper arm without riding onto my shoulders.

For reference, I'm 6ft 1in tall, and wore a size medium throughout testing.

The 100%-recycled polyester material was also comfortable and never caused any irritation or chaffing. I wouldn't describe it as soft, but it felt pleasant enough against my skin, and gets my seal of approval for its effective moisture-wicking and quick-drying performance on the trails.

The Tech 2.0 T-shirt obviously isn't waterproof or water-resistant in any way, but the fabric is hydrophobic and the garment sheds rain pretty quickly, and always dries off a few minutes after a downpour. I really appreciated this on long, hot treks, when more absorbant fabrics would've been weighed down by sweat.

The Tech 2.0 is still comfortable after multiple hours of testing and hasn't taken any significant damage. The fabric feels the same as it did when I first put it on, and design features, like the stylish printed Helly Hansen logo, look unblemished.

It's impossible to say what my Tech 2.0 will look like in a few months, but polyester offers excellent long-term durability.

Weight

At 6.7oz (190g), the Tech 2.0 T-shirt starts off lightweight, and it doesn't get soaked with sweat or rain. My T-shirts proved light and airy in all manner of weather conditions, and I never felt like it was weighing me down.

If you're looking for something uber lightweight to wear on the trails, you can find the 3.7oz (105g) Patagonia Ridge Flow running T-shirt, and others like it in our expert guides to the best running tops and the best hiking shirts.

Price

Along with its dependable quality and longevity in the wilderness, Helly Hansen gear is known for its hefty price tags. However, with a list price of $30 (£25), the Tech 2.0 T-shirt is actually comparatively cheap.

Also consider

Comparison table

• The best hiking shirts: choose one of these great fitting active tops with bags of technical clout
• The best running tops: for training and races on all terrains
• How Advnture tests products

First impressions

As with everything else in the new L.I.M. ZT II range from swanky Swedish outdoor brand Haglöfs, the Men’s Air Bottoms come with a hefty price tag that feels as though it weighs more than the garment itself. Can you justify such an outlay for a pair of boxer briefs? Well, that depends on how much value you place on being comfortable and staying cool when you’re at the crag, on the trail or making your way up a mountain.

While they look and feel very lightweight, these underpants (well, their designers and marketers) talk a big technical game. Over the last few months, I put my backside on the line to test the Men’s Air undies out, and get to the bottom of whether all these claims are legit, or whether the brand is talking a load of Swedish meatballs.

Design and materials

The Air Bottoms can be used as running underwear, used in conjunction with leggings or trail running short that don’t come with an integrated liner, or worn beneath hiking shorts and pants. But, if you consider that good base layers in general don’t receive the credit they deserve when it comes to the adventure wardrobe (and they really don’t), then underwear gets a proper bum deal.

In much the same way that hikers obsess about boots and shoes, and then don’t spend enough time pairing them with decent socks, people will pore over the pros and cons of climbing and hiking pants for hours, and then wear any old undies beneath them. Wiser hill walkers and mountain moochers will tell you that comfort starts at the bottom of the layering system, so the very first thing you put on when you get up on the morning of an adventure is crucially important.

Made with Polartec Delta fabric, these undies aim to keep the wearer cool and allow the body to breathe during dynamic activity. The material mix is an even split between recycled polyester (which is tough and long lasting) and lyocell, a substance sourced from plants which is relatively ecofriendly, comfortable to wear next to the skin, and can deal with the build-up of bacteria that leads to bad odors (obviously, you do still need to launder them regularly… it can’t do all the heavy lifting). There is also a pinch of elastane in the ingredients, which gives the garment dynamic stretch, keeps the underpants in place and helps maintain their shape.

Arguably the most important trick the Polartec Delta fabric brings to the pants party is the ability to wick moisture (sweat) away from the body with its hydrophobic yarns, before encouraging it to evaporate with its hydrophilic yarns. This clever process keeps the wearer cool, and dry, and reduces the risk of such adventure-ruining horrors as nether-region chafing.

However, the design and material mix also means they are supportive where it counts, and there is plenty of stretch in the fabric, so your range of movement is never impeded. Cleverly, the elasticated waist band, which keeps the underpants in place, perforated with hundreds of small holes, to make even that element of the garment more breathable and less sweaty.

On the trails and in the hills

I have been wearing the L.I.M. ZT II Men’s Air Bottoms for all kinds of outdoor pursuits over the last few months, from running around trails (beneath shorts, I hasten to add), to using as an underlayer for hiking, biking, scrambling and climbing. My review, in a nutshell, is that they’re excellent undies for any dynamic adventure activity in which you’re likely to break a sweat – which has been especially good during this multi-heatwave summer. They deal with sweat brilliantly, and never get clingy and uncomfortable.

Running shorts often come with an integrated liner, but many – such as the Adidas Terrex Multi Trail Running Shorts and the Rab Talus – don’t, which means you have to decide whether to go commando or wear undies while you tackle the trails. If you do choose to go with an underlayer, don’t go with a thick pair of cotton boxers or briefs, as these will quickly become sweaty and nasty, leading to discomfort and potentially horrible chafing issues. I found the L.I.M. ZT II Men’s Air Bottoms brilliant for running, because they’re supportive, very breathable and the Polartec Delta fabric very effectively wicks moisture away from your body.

Whilst hiking, climbing and messing about on mountains – where I have been lucky enough to pair the them with other items in Haglöfs’ new L.I.M. ZT II range, including the excellent Flex Trousers – the L.I.M. ZT II Air Bottoms have proved themselves as the perfect underpants. They permit a really good range of movement, so you can scramble over boulders, stiles and over obstacles, and reach out for footholds on the crag. And, as above, they keep you cool where it counts and reduce sweating and rule out any chafing problems by wicking moisture away.

Also consider

First impressions

Although it only comes in one color, the ZT II Air Base Layer top from Swedish outdoor gurus Haglöfs has a funky dot-pattern design that instantly makes it look satisfyingly technical. Design-wise it seems like a pretty standard, albeit good-quality long-sleeved base layer, but there is a bit more going on here than meets the eye.

The material mix, design and cut of the top all contribute to enhanced comfort and performance levels, especially when it’s paired with other pieces of alpine-orientated apparel in the Haglöfs’ new L.I.M. ZT II range.

It also has a splash of style, and can be worn as a stand-alone top in dry, warmish weather, when you still require a little bit of cover from the elements. With small reflective flourishes on each shoulder and a large neon yellow section on the back, the top makes you nice and visible on roads and tracks shared with vehicles.

Fabrics & design

A base layer might not seem like the most glamorous piece of kit, but as the garment upon which everything else is built, it’s extremely important. Wearing the right base will make a big difference to the enjoyment levels of any given escapade you set off on, but especially those that venture skywards, into the mountains.

The first job of a base layer is to provide a level of thermal protection, but if it’s itchy or uncomfortable, or if it fails to let your body breathe or adequately wick your hard-earned sweat away when you’re exerting yourself in the great outdoor alpine gym, you are not going to have a fun time.

Fortunately, the Haglöfs L.I.M. ZT II Air Base top does everything asked of it, with aplomb, and made with a thin and ‘cooling’ 115g/m2 knitted Polartec Delta fabric, it feels luxuriously lovely to wear. The material mix is half lyocell (an eco-sensitive plant-based fiber) and half recycled polyester, with a little bit of elastane thrown in to provide some dynamic stretch.

L.I.M. stands for ‘less is more’, and the signature element of everything in this range is that it starts off weighing very little, and remains light even if you sweat profusely or get caught out in the rain. Accordingly, the Polartec Delta fabric features both hydrophilic fibers (to draw moisture away from the body) and hydrophobic fibres to make sure it evaporates quickly.

Perfectly panelled to permit a good range of movement, the top is finished off with flat seams, to avoid any rubbing issues. The design is reasonably standard for a long-sleeved undergarment, but there are good features that make this top stand out, and mean than it can be worn with or without other layers, including reflective details, a nice crew neck, a hang cord and thumb loops on each cuff (something I really like to see on base layers).

On the trails and in the hills

I have been testing the Haglöfs L.I.M. ZT II Air Base top amid the craggy tors of Dartmoor and on the scenic, windswept summits of the Wicklow Mountains in Ireland. Although these peaks don’t exactly represent an extreme alpine environment, especially during the summer months, they are prone to low precipitation, and the prevailing weather conditions on Dartmoor and in the highlands of Ireland mean it’s always wise to wear a good base layer, and have plenty to put on over the top when the wind starts howling like a banshee, and the clouds come down to meet you.

The Air Base is the foundation garment for Haglöfs’ new L.I.M. ZT II range, and it can be used from sea level to the summit of serious peaks, if paired with the correct clobber from the rest of the range. During my recent adventures, I have been using this base layer alone, and with Haglöfs’ Air Midlayer and GTX waterproof shell jacket.

The ‘cooling’ Polartec Delta fabric used in this top is purpose designed for use during dynamic activity in warmer weather, so hiking on Houndtor and scrambling up the peaks of Great Sugarloaf, Maulin and Lugnaquilla in a temperamental summer – when the weather lurched from heatwave to horizontal rain – was a good test for the Air Base.

And it passed with honors. A bit like Merino wool, the Polartec Delta fabric does indeed possess the power to keep you warm when required – especially when used on conjunction with a midlayer like a fleece top, and a waterproof shell jacket or windbreaker – and cool when you’re working hard in more benign conditions. In my experience, self-generated moisture was effective wicked away from my torso, and the top very quickly dried out even when it became considerably sweaty (especially across the rear, when I was wearing a hiking pack). The Air Base also doesn’t cling to you like an insecure shower curtain when it does get damp, which is nice (and allows the garment to dry out quicker).

It also claims to prevent the build-up of bad odors, presumably thanks to natural enzymes in the lyocell content. I’ve only been wearing the Air Base for a few months so far (and I have taken it off on occasion), so I can’t fully verify this yet, but so far it has remained happily stink free. I love merino, but it is prone to wear and tear, whereas this top feels like it’s hardwearing and tough enough to last multiple seasons – which I would fully expect it to for the high price.

As mentioned, you can wear the Air Base as a stand-alone long-sleeved top, and I have done exactly that on a regular basis over the last few months. It’s not overly tight fitting (even over a gestating Guinness gut), feels good, and provides both thermal insulation from chilly breezes and protective cover from the sun.

While I was never cold while wearing the Air Base, I have been testing it in mainly warm conditions, while engaged in quite vigorous activity (where it excels), and there are certainly thicker and toastier under-tops out there, including some specifically made for thermal performance.

This top is just one piece of the clothing jigsaw in a modular series of layers, however, which Haglöfs’ designers have designed to be combined and used together in the mountains, to offer a level of performance and protection that defies their exceptionally low carry weight. And it does all work beautifully, but there’s no getting away from the fact that it is an extremely expensive ensemble to invest in, if you go for the whole lot. You can, of course, use the Air Base with other more affordable mid- and outer layers.

Also consider

If you want to get kitted out in something snug for your next camping, backpacking, or hiking expedition, then check out this insulating fleece from Columbia, which is now up to 64% off in Amazon's bargain bonanza.

The men's Sequoia Grove half zip fleece is made from 100% recycled polyester and is now available for as little as $21.47. It's designed for varied outdoor use with plenty of handy features and two zippered pockets to help you store the essentials.

Columbia says its sustainable polyester fabric is both stretchy and durable, so you can pull on your half zip every day in all manner of environments. It also features stretch binding on the collar, cuffs, and hem to help you seal out cold winds when the temperature drops.

The Columbia Sequoia Grove half zip fleece is available in loads of eye-catching colorways, including the earthy Delta / Ancient Fossil / Black and vibrant Razzle / Coll Navy.

Don't worry if you're not in the US, you can still find a great deal! Just look below for today's best Columbia fleece bargains where you are.

• The best hiking shirts: choose one of these great fitting active tops with bags of technical clout
• The best hiking shorts: tested and rated for summer adventures

Berghaus has revealed the first six recipients in its Adapts initiative, who'll receive custom kit to help them hit the wilderness.

The Berghaus Adapts initiative aims to make the outdoors more accessible for people living with disabilities by making bespoke alterations to their clothing and equipment.

The initiative launched in February and asked members of the public to request custom kit changes that Berghaus would then make. The British brand has now selected six members of the public, who'll work with Berghaus designers to create bespoke outdoor gear suited to their needs.

The six participants are of all ages and live with a variety of disabilities.

Meet the participants

William Kay

William Kay, from Tunbridge Wells in Kent, loves exploring the outdoors and playing football, but his Down syndrome makes it a little tricky to find the right kit.

William, 25, finds it particularly hard to get his hands on outdoor gear that fits his arms and legs well. The Berghaus Adapts team wants to work with William to create outdoor gear that he can wear to get outdoors in comfort.

Sarah Bowdidge

Sarah Bowdidge of Bridgend, Wales, dreams of scaling Yr Wyddfa (Mount Snowdon), but her disabilities have so far stopped her.

The 25-year-old has postural tachycardia syndrome (POTS), which means her heart beats at a faster rate than most, even when resting. She also lives with mobility issues. The Adapts initiative aims to help Sarah achieve her climbing goals with specially adapted kit to help manage her challenges on the mountain.

Hannah Baldwin

Devon local Hannah Baldwin suffered a climbing accident at the age of 12 and has since been unable to use her right leg. She was also diagnosed with Crohn’s disease, which further limited her ability to walk.

Hannah loves climbing regardless of her physical limitations, and scales walls with the use of one leg.

With the help of Berghaus Adapts, Hannah, who now needs support to walk, wants to push herself further and continue to pursue her passions in the outdoors.

Mark Hawkes

Mark Hawkes has always loved the outdoors and finds nature immensely helpful to his mental health. The 39-year-old Whitstable native now lives with inflammatory bowel disease (IBD) and has to wear a stoma.

To help Mark get back into the wilderness, designers from Berghaus Adapts are creating outdoor gear with accessible pockets, so the 39-year-old can access his stoma without hassle.

Will Weston

Will Weston, 43, became a full-time wheelchair user after a serious car accident in 2006. The Durham local was an avid outdoor lover before his accident, and wants to get back into nature to enjoy the wilderness with his nine-month-old daughter.

With the help of Berghaus Adapts, Will's also keen to summit Yr Wyddfa - a mountain he loved to climb before his accident.

Wendy Wright

In 1985 keen hill walker Wendy Wright was bitten by ticks in the Scottish Highlands. Some 15 years later, she was diagnosed with Lyme disease, which has significantly impacted her mobility for the past 25 years.

Now 63, Wendy wants to get back to her hill walking ways in custom Berghaus Adapts kit, specially designed to suit her unique needs.

• The best waterproof jackets: brave the elements with these top-rated hard and softshells
• The best hiking water bottles: stay hydrated at camp and on the trails

The North Face Summit Series Pro 120 Crew: first impressions 

A thermal base layer is an essential piece of kit for anyone who likes venturing into alpine areas, but not all base layers are created equal. While many opt for the magical benefits of merino wool, some, like the The North Face Summit Series Pro 120 Crew, recognize that synthetic materials can have their merits when you want long lasting protection from the elements.

This base layer is soft and light against the skin, but it has a secret weapon that ensures it is both warm in cold weather and helps you efficiently manage sweat once you layer up and get moving. What The North Face calls Double-Knit DotKnit Fabric is two layers of very light material with engineered holes in the face fabric to help sweat move away from your skin, so you don't get chilled when the going gets tough and you stay comfortable if it's milder than you expect outside. That means, unlike some synthetic tops, this one doesn't feel clammy and it dries in an instant when you get sweaty.

Two of the main issues with synthetic tops are that the material is essentially plastic, and therefore non-biodegradable, and that they can get really smelly as compared to wool tops. This one is made using 100% recycled fabric, for a kinder footprint, and it's treated with anti-odor protection. We've found we can get a few wears out of it before it inevitably starts to pong.

It's got a slim fit, which seems to make up for the lack of stretch (which in turn means it should keep its shape longer) and has long sleeves with thumb holes for added hand protection, and is a good length for decent coverage.

It's not exactly cheap, but compared to other base layers we've tested, it's about middle of the price range, and while it's definitely aimed at colder weather adventures where you'll be wearing it with other layers, on its own it could make a decent top even on chillier summer adventures.

The North Face Summit Series Pro 120 Crew: in the field 

I got this base layer to test out on a whirlwind trip to Courmayeur where, among other things, I got to attend the launch of Jeep Avenger 4Xe TNF edition and do some glacier hiking in whiteout conditions. Since then, I've been wearing it all winter here in Scotland for hiking.

Here’s how it performed:

Sizing, fit and comfort

I tested a small, which is my usual size, and it's a perfect fit. It doesn't have any stretch, but I don't have any problems getting it on and off and of course, zero stretch means it won't lose its shape, or not for a long time anyway.

It's got a longer cut so it's easy to tuck into my rain pants or just offer a little more protection from the cold around my hips, and long sleeves with thumb holes. This can be annoying when trying to look at my GPS watch of course, but it also means added hand protection when it's cold.

It's well designed with raglan sleeves and not tight around my shoulders or middle so it's comfortable in fit as well as being soft against my skin, but the slim fit means it's also easy to layer with mid layers like my Houdini Power Hoody.

Temperature regulation

I usually swear by merino wool for my first layer, but I've been venturing out into synthetic tops this winter with a fair degree of success. This one doesn't initially feel like a thermal top, but upon closer inspection I realized that the double layer does hold in heat, and I was happy to have it on an alpine glacier as well as up multiple Scottish Munros this winter.

The double layer of DotKnit Fabric is really just tiny holes in the face fabric, but it seems to work a charm. The brand claims this speeds up moisture transfer from skin to surface and of course I can't say for sure that it does, but I can say that I can hike up a steep mountain wearing this with a fleece and waterproof and never feel damp or clammy, which is all I can ask for.

Like a lot of The North Face's tops in recent years, it also dries astonishingly quickly when my back has got sweaty from carrying a pack, which is another big bonus in colder weather.

Odor control and other features

I've grown a bit skeptical when it comes to claims of odor-control in synthetic tops. Synthetic materials just get smelly. But that said, I can tell that some effort has been made to mitigate this eventuality, and I've worn this several times before I've felt I needed to wash it, which is a good start.

Other than that and the thumb holes, there aren't any other great special features to speak of when it comes to this base layer.

The North Face Summit Series Pro 120 Crew: the bottom line 

If you're looking for a synthetic, technical base layer, you won't find much to argue with here. This top is excellent for high output adventures in cold weather where you want to stay warm, manage moisture and dry off quickly. It's probably too warm for summer pursuits, but if you're in a chillier climate or find yourself at altitude, it's fairly protective on its own.

Also consider

Comparison table

• How Advnture tests products

While these long-length sports trunks from Reebok aren’t specifically designed for one specific activity – you can wear them while working out in the gym or when wandering wild trails – the materials used and well-ventilated design immediately recommended them to me as potential contenders for our guide to the best running underwear, and this is the context in which I have been testing them.

Many of the best trail-running shorts come with an integrated inner these days, but not all. While there are lots of excellent double-layer shorts out there, such as the Inov-8 Trailfly Ultra 7" 2-in-1s, separation of inner and outer can be a good thing – not least because some included inners can be poor quality, and/or might deteriorate much quicker than the outer – and there are plenty of excellent running shorts, such as the Rab Talus and the Adidas Terrex Multi Trail shorts, which are single layer. Also, some people prefer to use running leggings, rather than shorts. There’s a live debate about whether it’s best to wear underwear beneath shorts and leggings or go commando, but for reasons ranging from chafing to chastity I prefer to layer up.

And whether you’re running trails or hiking them, this is the best way to approach this garment: as a base layer for your nether regions, which makes it the all important starting point for every other layer you put on. Just like the performance of your carefully selected trail running shoes will be enhanced by pairing them with good running socks, so you will get the best returns from your shorts and technical running top if you start with the right foundation.

Design and materials

Reebok have spurned the use of natural materials such as Merino wool in the construction of these undies and have instead gone for an entirely synthetic build, and the garment contains just two components: polyester (for the main part) and elastane (to supply support and allow dynamic stretch while maintaining shape). There are pros and cons to this, which I will go into below, but in terms of design these trunks are primarily intended to do a couple of things. The first of these is to allow your body to breathe during high intensity exercise, which is facilitated through the mesh design and moisture-wicking material used in the main panels. The second is to supply some support to your thigh and gluteal muscles, and keep bits of your body in place to minimise movement, which can lead to discomfort – these tasks are achieved by use of elastane throughout the relatively long trunks, which extend to the mid thigh, and the inclusion of a front pouch in the design.

On the trails

I have spent the last couple of months running and hiking in these long-length Reebok sports trunks (don’t worry, they come in a pack of three, and being made of synthetics they’re easy to launder – this is definitely one of their strong points).

As the weather has warmed up, I have found the moisture-wicking properties of the material and the mesh design of the undershorts to be very effective at preventing overheating and excess sweating, which can of course lead to nasty chafing and all sorts of other best-avoided dramas.

I even wore the Howes Long Sports Trunks during a running session in a heat chamber designed to simulate the desert conditions faced by competitors taking part in the Marathon des Sables, and while taking a sweat test, and they performed well in the 38°C conditions I encountered there. Besides wicking moisture away from the body, and allowing plenty of air flow to the places where you need it, the poly material and mesh design used in these undershorts dries out very quickly.

Although lacking the sumptuous nest-to-skin feel of merino undies (like the high-end Artilect M-Boulder 125 Boxer Briefs) these shorts are comfortable to wear, and have not yet felt abrasive (I hope this continues after multiple washes). Although mesh can be prone to perishing, the synthetic fabric employed in the Howes is hard wearing, and these pants come in a pack of three for a much more affordable price than their merino counterparts. My main concern with the materials used is that they don’t have the in-built anti-bacterial superpowers that natural fibers boast, and as far as I can see no treatment has been applied, so over time they might accumulate stubborn sweaty odors. For the same reason, you can’t get really wear them for multiple days on the trail when fastpacking.

The design of the shorts, with the supportive pouch and thigh and glute-gripping legs, does make these very comfortable undies to wear during quick-paced activities such as trail running and bikepacking, and they give you complete confidence while you’re out and about. But the importance of wearing good undergarments while walking is often overlooked, and I have also very much enjoyed wearing these trunks as a base layer beneath hiking pants during the spring months. They’re also good for climbing adventures. The material is stretchy as well as supportive, so your range of movement isn’t impeded at all, and the wide waistband is particularly good at keeping the trunks in place without being too tight or uncomfortable.

Columbia Omni-Heat Midweight Baselayer Tights: first impressions 

From the outside, this pair of thermal underwear just looks like your average pair of stretchy leggings, but check the lining and you'll see they possess a secret superpower. Covered with tiny silver dots otherwise known as Columbia's Omni-Heat technology, these leggings act just like an emergency blanket, reflecting your body heat back to you during those chilly lift rides or winter camps.

If you're working up a sweat skinning uphill or snowshoeing, the Omni-Wick fabric construction allows for truly excellent breathability and in our field tests, we found these leggings delivered amazing sweat-wicking properties and dried in a flash once we stopped moving.

The polyester fabric is also treated to manage bacterial growth, and we've worn them for multiple hikes and ski tours without needing to wash them, which suggests they'll last longer. With a comfortable, wide waistband and tons of four-way stretch, they're also perfect for yoga which means we can pack light for ski trips.

The super-light fabric is also really easy to layer over when you're donning ski pants or hiking pants. The price on these is great, especially since they're so versatile, and the only thing we'd like to see in the future is some recycled materials used for sustainability.

Columbia Omni-Heat Midweight Baselayer Tights: in the field 

I've had these thermal leggings for nearly five months, and been testing them alongside the Columbia Omni-Heat Midweight Baselayer Crew. I initially got them for a hut trip in the Swiss Alps in the fall, but it wasn't actually very cold, however I did wear them for a chilly sunrise yoga session. Since then, I've worn them for a few frigid winter hikes in Scotland and the Lake District, and more recently got to give them a proper test drive in Verbier where I was alpine skiing and ski touring.

Here's how they performed:

Sizing, fit and comfort

I tested a small, which is my usual size, and they're perfect, exactly as you'd expect leggings to fit. The shiny lining doesn't look like it's going to feel good against the skin, but there's really nothing tin foil about these leggings which are surprisingly soft. They're comfortable in a "barely-there" way like my favorite yoga pants and I never have to stop and hike them up.

Speaking of yoga pants, they are stretchy as you get, and I've worn them for yoga several times including on an alpine deck on a chilly morning. I love that they can double up, because it meant that I could pack light and still have everything I needed for skiing and stretching without checking a bag.

Temperature regulation and moisture management

Obviously, the most important thing I expect from a pair of thermal underwear is warmth, and these deliver that by the ladle. If you've never tried any of Columbia's Omni-Heat garments, it isn't a gimmick – I really do feel instantly warmer wearing these, and I love that that warmth isn't provided by thick fabric or itchy wool.

On my last day in Verbier, I decided to rent an AT set up and go on an 8k ski tour up the mountain. The first half was mellow, followed by some fairly steep climbing through untouched powder. I was a little overdressed, because I hadn't planned or packed for touring, and it wasn't the coldest day (in fact, it was raining in the village). So, I was expecting to be too warm and nearly didn't wear these. I'm glad I did, though.

In action, these pants do exactly what they claim, which is to wick sweat even under fairly warm conditions. I never felt too warm or remotely chilly during my adventure, and when I met my colleagues for lunch, they dried out almost instantly, which meant I could then sit outside on a cool, sunny deck without feeling cold.

Durability and odor control

These leggings are described as medium weight, but they feel really thin and light, which would normally make me wonder about their durability, but there's nothing flimsy about them. As I said, I've been testing them out for nearly five months and they still look brand new.

That's in part because I've barely had to wash them. They have an antimicrobial treatment that wards off odors and even after sweating uphill in them, they don't really need a wash (though I'm going to wash them, I promise) so I can see them lasting longer than other synthetic garments that can get really smelly.

Columbia Omni-Heat Midweight Baselayer Tights: the bottom line

I'm going to go out on a limb here and say that these are currently my favorite thermals for winter adventures. They're light, stretchy and can handle sweat like a boss. They also double as yoga pants which is super compelling for me, and they come at a good price considering their built with NASA-inspired technology.

All of my other thermals are made from merino wool, so it's hard to compare them, but if you prefer the magical powers of merino then I suggest you look no further than the Smartwool Intraknit Merino 200 bottoms.

• How Advnture tests products

Reebok Teresa Racer Back Bra: first impressions 

The Reebok Teresa Racer Back Bra is marketed as an everyday sports bra, though we found it more than sufficient for higher-intensity pursuits like long trail runs and HIIT workouts. Crafted from stretchy polyester, it's easy to pull on and off – even when you're sweaty – and dries in a flash to keep you from getting chilled after a long run or hike.

Though we hardly have to wrestle to get into it, once it's on we've found that it delivers all-day comfort and support without any rubbing or chafing.

The racer back design means this bra can be worn with whatever running top or hiking shirt you want to pair it with, while it's flattering enough to be worn on its own when things heat up. It puts the Reebok brand front and center with a large logo across the front, which isn't everyone's cup of tea.

Choosing a sports bra is a really individual thing, and we're not sure this one is built for larger breasts (it also doesn't go up to an XL). There aren't any mesh panels for ventilation, though that hasn't posed a problem so far, and the neckline could be a little higher for sun protection. All that said, it's comfortable, does the job and comes at a great price.

Reebok Teresa Racer Back Bra: in the field 

I've been wearing this bra for the last couple of months, which means it's been on about 220 km worth of hikes and trail runs in Scotland, the Lake District and the Italian Alps as well as to a weekly HIIT class and regular yoga classes.

Here's how it performed:

Sizing and fit

I tested a Small, which is my regular size, and I'd say it first true to size. I'm fairly small but have a pretty muscular upper body and it's snug – I do have some faint marks from the chest band after wearing it – without being overly tight or causing any unwanted bulging. It's also surprisingly easy to get in and out of despite being so snug.

In general, I like a raceerback design which can be worn with a tank top, though if I were a person who likes to run in just a bra (I'm not), I wouldn't mind the neckline being a bit higher to protect my chest from the sun.

Comfort and support

This bra doesn't have loads of stretch, but it's very comfortable to wear all day long, which I've done numerous times. I haven't had any rubbing in it, though I can't promise that it wouldn't start to chafe during a 100-mile run.

I have small-to-medium-sized breasts and this bra really provides what I'd call a lockdown fit. Reebok warned me that it isn't meant for running, but I honestly can't see why as I have done all sorts of sprinting, jogging, jumping and burpees in this with no issues at all.

I'm fairly certain this design wouldn't work for larger breasts, but if you're in the medium or smaller range, it should keep everything in place.

Moisture management

Besides comfort and support, I want my sports bra to dry quickly, because there's nothing worse than damp underwear after a long run, especially during the colder months. Of course, this gets damp when I sweat but it doesn't get soaked and dries really quickly, which I think is the main reason it keeps on ending up back at the top of my pile.

It doesn't have any breathability mesh panels, but so far I don't think it really needs them.

Reebok Teresa Racer Back Bra: the bottom line

If you're seeking a supportive, versatile sports bra for small or medium sized breasts, this has a straightforward design but exceptional quick-drying properties making it a good choice – and at a very budget-friendly price. If you need more support, check out the Pure Lime Compression Bra instead.

• How Advnture tests products

Over at REI, there's a huge winter sale happening on all the best merino wool gear from Smartwool. Right now, you can pick up the top-rated Smartwool Classic Thermal Merino Quarter-Zip Base Layer Top for just $89.99 at REI. That's a healthy savings of 25% off the regular asking price for this winter base layer, which hikers give a very rare perfect 5-star rating.

I received this base layer as a gift 15 years ago when I first moved to Vail, Colorado, and I've been wearing it for hiking and skiing ever since. It's soft against my skin and though the slim fit makes it ideal for layering, it's not too tight.

Thanks to 100% merino wool fabric, I can work up a good sweat in this top while skinning or hiking up a mountain in winter and still stay warm, plus it doesn't get stinky like synthetic tops. It's built for cold weather, but it's light enough that I bring it along as an extra layer for summer adventures too, and the 3/4 zip means I can cool off a little if I need to.

This deal applies to both men's and women's sizing in all colorways through November 25, so grab yours now for a winter of warmth and comfort.

If you're looking for other apparel, we're keeping tabs on all the best deals in REI's big winter sale for you.

Not in the US? scroll down to the bottom of this article for today's best deals on Smartwool Classic base layers where you are.

I love this top so much that I ended up buying two more in different colors, but I have to say that it's the original Twilight Blue Heather that I wear the most and that has come with me for my move back to Scotland.

If you're not in the US, here are today's best offers on Smartwool Classic base layers near you:

• The best base layers: the foundation of your hiking garb

Meet the reviewer

Columbia Omni-Heat Midweight Baselayer Crew: first impressions 

Columbia introduced its Omni-Heat technology back in 2010, which takes the NASA-inspired technology that is used in emergency blankets and applies it to apparel. But like most technology, it's taken a few tries to get it right and lately, the company has taken some big strides. First, there was the ultra cozy Arch Rock Double Wall Elite Insulated Jacket which can fend off practically any amount of chill, and now there's this toasty base layer.

Made using elastane stretch jersey, the outer of this base layer gives a smooth, simple appearance, but it's what's on the inside that counts. Lined with tiny silver dots that look like foil everywhere but under the armpits, this base layer is designed to keep recycling your body heat while allowing water vapor to escape thanks to Omni-Wick fabric and the spaces between the dots.

A foil-lined base layer really might not sound very comfortable, but trust us –  this one feels good against bare skin. Though it's listed as midweight, it's pretty light, making it really easy to layer and move in thanks to four-way stretch and ergonomic seaming.

It's a synthetic top, so it's going to get smellier than one made using merino wool, but a zinc-based antimicrobial treatment helps to hold off the laundry cycle and you can definitely sweat in it several times before it needs a wash. It doesn't have thumb holes and it's not made using any recycled materials, which is always a pity, and obviously it's not designed for warm weather hikes, but for cold weather? It packs a real punch.

Columbia Omni-Heat Midweight Baselayer Crew: in the field

I was a little late to the game with Omni-Heat technology, only discovering it last year in the Arch Rock Double Wall Elite Insulated Jacket which is so effective I actually keep it in my car now in case of emergencies.

I recently traveled to the Swiss Alps with Columbia to test out some of their new gear and this was one of the items I received. I'll admit, when I pulled it out of the box and saw the shiny lining, I was a bit skeptical. However, I dutifully took it to the mountains where I wore it for very chilly sunrise yoga as well as some high altitude hiking, and more recently I've been wearing it in the Cairngorms of Scotland for my hikes now that the weather has turned colder.

Here’s how it performed:

Sizing, fit and comfort 

I tested a women's small, which is my usual size, and it's a perfect fit – snug without being too tight. Now, it does have loads of stretch, so there's some wiggle room, but I'd recommend just ordering your usual size if you want a close-to-the-skin fit that's easy to layer and does the best job of wicking sweat.

I like the high crew neck, which meant I got good sun protection recently when I ended up removing my jacket on a bright day.

Surprisingly, the lining isn't at all uncomfortable and in fact, I wore this top with the matching long johns for yoga and it felt great against my skin. It's light, soft and stretchy without any rubbing anywhere.

Temperature regulation and breathability

Obviously, this base layer is designed for warmth, so while I wouldn't wear it in the summer, I'm finding it great for any temperatures from just cool to really frigid. That's because it's really breathable, thanks in part to the omission of reflective lining under the arms as well as really breathable fabric. So even when I was hiking up the steep slopes of Ben Vrackie last week at 1,000 feet per mile and wearing a fleece over the top, I didn't overheat.

In fact, though I was sweaty in the usual places (underarms and where my backpack sits), I didn't even feel particularly damp. When I arrived at the summit, it was really breezy and cold, so I had to pull on my waterproof jacket fast. I expected I'd have to rush off the summit, but the genius of this technology is that even when you're damp and it's cold and windy, it keeps reflecting your body heat back to you, so I quite happily sat and ate my sandwich.

I only had to walk about a mile down the trail before I had to remove my outer layers again, and I noticed that the shirt had dried out really quickly. Obviously I wouldn't wear this for a warm summer hike, but I think it's brilliant for colder conditions and light enough to be layered or worn alone if it's mild out.

Odor control and other features

Odor control is always an issue with synthetic tops, and it's one of the reasons I usually go for merino wool, but this one is treated with an antimicrobial substance and I have to admit that it works quite well. I've had several outings without needing to put it in the laundry, though I'm not sure what the durability of these types of treatments is.

It doesn't have any thumb holes, and I know these are a feature many people look for in base layers. Personally, I think the sleeves are tight enough I don't need them for layering, and because it's for cold weather, I'd typically be wearing it with gloves or a fleece with thumb holes anyway.

Columbia Omni-Heat Midweight Baselayer Crew: the bottom line

If you want a seriously warm base layer that's not merino wool, look no further than this one, which blends state-of-the-art insulating technology into a breathable, straightforward and comfortable first layer. This top is built for cold weather, whether you're hiking, skiing or ice climbing. If you're still on the hunt for something super warm and want a merino blend that's great for sensitive skin, compare it with the Helly Hansen Lifa Merino Midweight Crew.

• How Advnture tests products

Right now, you can pick up the flattering and functional Smartwool Women's Active Ultralite High Neck Tank for just $41.73 at REI. That's a healthy savings of 24% off the list price for this lightweight merino wool running top that we loved in our field tests.

I've been hiking and trail running in this top all over Europe this year, from the volcanic island of Gran Canaria to the world-famous trails of Chamonix, and I love how soft, light and fast-drying it is. The drapey fit of this tank top means more air moving around your body while you run, and it looks great, so I often wear it off the trail too. 

The merino blend is soft, light and pulls sweat away from your skin while the cut offers a little more sun protection than your typical racerback. Best of all, it has excellent odor-control properties so I can wear it again and again without needing to wash it.

This deal applies to the Guava Pink and Limeade colorways in all sizes, but we recommend acting fast to ensure you get the size you want as REI has discontinued this model. 

Not in the US? Scroll to the bottom of this article for today's best deals on the Smartwool Women's Active Ultralite High Neck Tank near you.

We love this top for active travel, because it regulates our temperature and it's stylish enough to wear off the trail with a pair of leggings or joggers, which means we can pack lighter and avoid checking a bag.

Not in the US? Here are today's best deals on the Smartwool Women's Active Ultralite High Neck Tank near you.

• The best women’s running tops 2024: for cool and dry runs on the trails or roads

Meet the reviewer

BAM Women’s Novea Crew Neck Training Top: first impressions 

For high-intensity adventures, you don't always want a synthetic top which will dry quickly but stink, and not everyone feels good about animal-based products like merino wool. This women's running top is built to offset some of those concerns. Made from plant-based fibers including bamboo and Naia Acetate (a cellulose-based fabric), the Novea Crew Neck Training Top is unbelievably soft against your skin.

With a snug, stretchy fit, it moves when you do and is easy to layer, while the high neck gives good sun protection during summer runs and hikes. Arguably its biggest selling point is its exceptional odor control. In our field tests, we couldn't believe how many hours we were able to sweat in this top without it needing to be washed.

There are, however, some downsides to using fabrics like bamboo and this top still falls victim to those shortcomings. Though it dries quicker than the Naia base layer we've previously tested, it still gets damper than wool or synthetic and holds moisture longer if you don't hang it out to dry. This means you can get chilly if you stop for a break.

It's also not the most durable fabric, and ours is already showing signs of wear and tear even though it's yet to be washed. It's not perfect, but it is extremely comfortable and has some benefits for multi-day adventures where you don't have laundry access and are expecting sunny weather, plus it comes in well under many other running and hiking tops in terms of price.

BAM Women’s Novea Crew Neck Training Top: in the field

I just returned from a 40km trail running trip in the Swiss Alps. I needed to carry everything that came with me on my back, so it was important to me to bring a top that wasn't going to get smelly and could handle three days of sweating. Having worn this top for a couple of runs closer to home and noticing that it didn't get smelly, I decided to test this out as my running top on my trip.

Here’s how it performed:

Sizing, fit and comfort

I usually wear a size 8 UK (4 US) and that's what I tested and I'd say it's perfect. It's snug without being skin-tight or digging in everywhere, and I was able to pull a long sleeve over it if I needed to. The crew neck meant I got good sun protection on my chest, which I really appreciated. The Raglan sleeves and panelling sadly aren't very flattering on me, but I think the problem is my body and not the actual top.

That said, I didn't much care how it looked because it feels amazing. Like any bamboo product I've worn before, it's just buttery soft against my skin and I can imagine really loving this if I were sensitive to other fabrics.

Temperature regulation, breathability and moisture management

I've been wearing this during steep hiking and trail running in mostly warm temperatures and it's great at keeping me cool under those conditions. The loose weave means it breathes really well and it's a much better choice for summer adventures than synthetic, in my opinion.

That said, a major drawback is that it does hold more moisture than my wool or synthetic tops, so when I stopped for a break, I did find that I got a little chilly. The weather wasn't cold enough during the day for it to be a real issue, and I had brought along an extra top to wear in the evenings, but it would make this top a problem in colder, damper weather. I found it dried completely overnight when I hung it up in the cabin, but yesterday at the end of my last run I chucked it in my backpack for the flight home and just opened it 24 hours later to find that it's still damp.

In short, it's great for warmer and more arid climates, but not for cool, damp weather, and you'll want to be able to dry it properly between uses.

Odor control and durability

Where I think this top really excels is in how well it handles odor. After a few runs at home, the armpits didn't stink at all, so I took it to Switzerland without washing it first, then wore it for three days of running and hiking while wearing a backpack. I got very sweaty, but the top did not get smelly. I'll give it a wash now I'm home to freshen it up, but at a push I could definitely wear it another time or two and this makes it a great choice for multi-day adventures.

Sadly, it's already showing some pilling across the back where it was coming into contact with my backpack so I don't necessarily see this as having the longevity I might want, but I also think it's priced accordingly.

BAM Women’s Novea Crew Neck Training Top: the bottom line

If you need something super soft and hypoallergenic that holds up against multiple high-intensity adventures, there's no doubt you'll love the feel of this lightweight tee, however, it's best suited for warmer, dry conditions, especially if you can't dry it out properly between uses. It holds moisture a little longer than merino and doesn't seem to be the most durable top we've tested.

If you don't mind a top with animal origins and need something that's better suited to cold and wet weather, check out the Icebreaker Women's Cool-Lite Amplify Short Sleeve Low Crewe T-Shirt as an alternative.

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Arc’teryx Silene Crew Shirt SS Women’s: first impressions 

If you've had enough of hiking and climbing in old cotton T-shirts and are ready to upgrade to a performance-ready top, this hiking shirt might just be for you. Spun from ultra-light polyester yarn, it's built to withstand the demands of backpack straps, harnesses and abrasive rock but still soft and comfortable on your skin.

The best feature of this shirt is its moisture-management capabilities, whisking sweat away from your skin on a hot climb without ever feeling damp. It breathes exceptionally well and dries quickly so you don't get chilly on a windy summit when you stop for a breather.

The relaxed fit means that even without added stretch, this airy top easily moves when you do so it never feels restrictive, and the Raglan style sleeves and hemming technique cut down on seams to minimize chafing. That said, we found the design to be slightly off with the neckline not sitting flush against the skin.

As far as T-shirts go, it offers decent coverage to help protect your skin from the sun and though it's a synthetic top, it is treated with an antimicrobial agent which does seem to reduce how smelly it gets with wear. It's treated with DWR which is unusual for a T-shirt and we're not totally sure why, since we'd be more likely to throw on a light waterproof jacket if it starts to sprinkle and it's very quick drying anyway. 

All in, we do enjoy the feel and performance of this top, but it does come in at quite a high price point, perhaps unsurprisingly given the brand. Learn more in our article on why Arc'Teryx is so expensive.

Arc’teryx Silene Crew Shirt SS Women’s: in the field

When it comes to hiking and climbing, I basically have two merino wool T-shirts that I rotate through for every adventure. I love that I can wear them multiple times in a row without them getting smelly, I like the feel and thermoregulation properties of wool and in general, they're a bit less sporty which makes them a bit more me. However, I got to test out this top recently when I attended the Arc'teryx Climb Academy in the Lake District and wore it for some scrambling, bouldering and hiking.

Here’s how it performed:

Sizing, fit and comfort

I usually wear a small but I'm probably on the small end of that size range so I tested an XS in this shirt and that was the right choice for me. It has a relaxed fit which lets me move, but isn't baggy. That said, there is something very odd about the design of this shirt, so the neckline doesn't sit flush against my skin but rather sticks up all around. It wouldn't stop me wearing it on the trail, but it does look a bit off and I doubt is intentional.

Before I noticed that however, I did notice how comfortable this top is. Even though I've said I usually prefer the feel of a merino wool blend, this polyester is lovely and soft against my skin and they've cut down on seams (which may account for the strange neckline) so I haven't experienced any chafing.

Moisture management and breathability

As far as I'm concerned, the best thing about this shirt is how well it manages moisture and I'd recommend it to anyone planning on hiking or climbing in hot weather, or who sweats a lot and is tired of their clothes clinging to them.

I'm not a particularly heavy sweater, but we've enjoyed some warm weather here lately and this fabric has that magical quality of never feeling damp. I've only experienced this before in The North Face Flight Series Weightless Tank Top which isn't as soft and comfortable as this shirt. I've even tested this out on a couple of trail runs and it's great at keeping me dry and comfortable in warm weather.

I recently wore it during a warm, very steep hike and it breathed really well the whole way up. When I got to the top and removed my backpack, my back was of course a bit damp but the shirt was completely dry within in minutes.

Durability and odor control

The obvious benefit to synthetic material over natural fabrics is that it's more durable, and I do trust this top to look good as new in a year's time (though I'll be sure to update this if I'm proven wrong). The lack of added stretch from elastane also bodes well for it to keep its shape.

Ordinarily, synthetic tops need washed after every use because they absolutely hum, however, and in my mind that cuts down on their durability (and sustainability of course). This one is treated with some kind of antimicrobial and while I wouldn't exactly say the armpits smell delightful, I've now worn it about six times without washing it and I'm planning on wearing it again today. That's a record.

Arc’teryx Silene Crew Shirt SS Women’s: the bottom line

This unassuming-looking tee is a top-performer for adventures where you plan to sweat. It's highly comfortable and light but durable and keeps body odor at bay for a couple of jaunts. For that, you'll pay a premium price for a T-shirt, but it is versatile enough that you could wear it for many different types of activities and that may soften the blow. We recommend trying it on before you commit to see how you feel about the neckline, and compare it to The North Face Bolt Tech T-shirt for an option that's easier on the wallet.

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Smartwool Women's Active Ultralite High Neck Tank: first impressions 

This women's running top is designed for those of you looking to stay cool and dry even on warm weather runs (and hikes). A blend of merino wool and lyocell feels soft against your skin and wicks sweat away as you warm up, drying quickly so you don't get chilled when you stop for a drink of water.

The relaxed fit of this tank might not be to everyone's taste, but we found that it helps to keep us cool on hot days, and it's quite flattering. The high neck and back also offers more sun protection across your back and shoulders than your average racerback for running in.

With flatlock seams and a looser fit, we have yet to experience any chafing with this design and the wool properties mean we've been able to put quite a few hours in it without it getting stinky. This is a big plus, especially because wool is known to degrade faster than synthetic materials, and fewer washes equals more wears in the long run.

We love this top for active travel, because it regulates our temperature and it's stylish enough to wear off the trail with a pair of leggings or joggers, which means we can pack lighter and avoid checking a bag.

Smartwool Women's Active Ultralite High Neck Tank: in the field

This winter, like most, hasn't exactly brought a lot of tank top weather to Scotland, so I've been biding my time until I can test this top out. Smartwool is based in Colorado, the state I called home for many years, so it's near and dear to my heart and I hoped it would be a great addition to my running wardrobe. Finally, it warmed up here and I got it out on a few warm park runs before taking it to Gran Canaria recently on a hiking adventure.

Here’s how it performed:

Sizing and fit

I tested this top in a small, which is my usual size and I'd say it's perfect, given that it's meant to have more of a drapey fit. That said, the design probably allows for you to size down if you don't like things too loose, or size up for more room.

As for the fit, I owned a yoga studio with a boutique for long enough to know that not everyone loves this style of top, but those who love it really love it. I personally don't love the way it looks on me when it's not tucked in, but quickly realized I like it tucked, and this helps avoid any potential chafing from my shorts. 

The high neck and drop tail means it offers about as much sun protection as a tank top possibly can, and I think it's versatile enough to work for lots of people.

Comfort, breathability and moisture control

This top instantly felt really comfortable compared to my synthetic tops. I'm certainly predisposed to prefer natural fibers, but it's soft, light, loose, stretchy and comfortable, even when I wore it all day long in Gran Canaria where a typical day included a long hike and a car journey to another part of the island.

I wore this top for hiking and running in temperatures in the upper 70s and was really comfortable. The breathable fabric combined with the loose fit means it's perfect for warmer weather.

In general, merino is good at wicking sweat, though you'd normally want the material to lie closer to your skin to be the most effective. This is a little looser, and I'm not a huge sweater, but I didn't have any issues witch clamminess even when hiking in the warm weather wearing a backpack.

Durability and odor control

I haven't been wearing this for long enough to know how durable it is, but what I do know is that merino wool in general isn't as long lasting as synthetic material. On the other hand, I currently own base layers from Smartwool that are 15 years old and they're still going strong. 

Only time will tell, but I do know that I've been wearing this across multiple sweaty activities for about a month, I've yet to wash it and it's yet to get stinky. That means I can get away with washing it minimally, and if I follow the care instructions I hope it will last a few years at least.

Smartwool Women's Active Ultralite High Neck Tank: the bottom line

In terms of performance, this running top will stay fresh and keep you cool and dry, so the only reason we can think of to not choose it is if you don't like the cut and style of it. It's great for running, hiking and can be worn with regular clothing too if you're on an active vacation. If you're more of a synthetic racerback type of runner, check out the totally different Flight Series Weightless Tank Top from The North Face instead.

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The North Face Trailjammer T-shirt: first impressions 

Sweaty adventures require the work of a technical tee with breathability at the forefront, and in this hiking shirt, The North Face has prioritized keeping you cool whether you're hiking, mountain biking or clinging to the cliffside.

Built from perforated polyester, which essentially has lots of tiny holes in it, this sporty, performance-oriented top is very airy when the sun is beating down on you during a steep climb, and easily whisks sweat away from your skin to help cool you down.

A crew neck and medium-length sleeves provide decent protection from the sun, while it's designed with side splits and a dropped tail to be appropriate for mountain biking. This also means you have extra coverage when hiking with a backpack. A streamlined (but not snug) fit leaves plenty of room for comfort and mobility, with lots of stretch added in.

For the most part, flatlock seams cut down on chafing, but the front of the neckline feels a little stiff and rough and some hikers might experience some chafing. Like any synthetic fabric, it gets stinky quickly but we're pleased to see it's largely constructed using recycled materials. It's made of tough stuff and performs well as a first layer or on its own across a variety of adventures.

The North Face Trailjammer T-shirt: in the field

I got to test this hiking top out on a press trip to Corsica with The North Face in early April, where I wore it as a first layer on a cool hike and mountain bike ride, then on its own during a hot, sunny via ferrata. 

Here’s how it performed:

Sizing and fit

I tested a small, which is my regular size, and I think it's true to size. In fact, for once it actually fits me light the model on the website. It's not tight, but not so loose that it won't wick sweat and in general I'd say it's a comfortable fit where I can move but also layer something on top.

The sleeves aren't too short, so they give a little sun protection, and the back is a bit longer than the front which is intended for mountain bikers, but also comes in useful when hiking with a backpack.

Comfort and breathability

I spent several days adventuring in comfort while wearing this shirt. It has plenty of stretch and the fabric feels nice against my skin. The only potential issue I spotted is that the seam on the front of the neckline is really stiff when I run my fingers over it and feels a little rough to the touch. I didn't personally experience any chafing on my adventures, but I can imagine that if this were to fit a little tighter, it might cause problems for some.

I wore this as a first layer with The North Face Bolt Polartec Power Grid Pull-On Jacket while hiking and with The North Face Windstream Shell Jacket review while mountain biking. Later, I wore it on its own on a via ferrata where it was hot and sunny. In all of those configurations, I never got overly hot or sweaty. I think the perforated polyester works great for breathability and sweat-wicking.

Odor control and durability

This shirt is made using synthetic fabric, albeit a recycled one, and that means that it does get a bit stinky quite easily, and will stay that way until you wash it. I wore it over three days and while I wasn't exactly humming, it was ready for a wash. I did let it sit for a couple of weeks before washing it as an experiment, but that wasn't enough to air it out.

That of course means that you'll have to wash it frequently, which always cuts down on its durability, but overall it's a pretty tough top. That said, The North Face's FlashDry fabric is designed to be snag-resistant, but I did manage to snag mine on a very thorny bush while biking. However, I also drew quite a bit of blood so I'm under no illusions that any shirt would have held up against that. 

The North Face Trailjammer T-shirt: the bottom line

If you're looking for a tough, versatile top that you can wear for hiking and biking in hot weather, this one affords you lots of breathability. The sporty design may not be for everyone, but the focus on performance will please those who want to get moving. If you're looking for something slightly more stylish, The North Face Bolt Tech T-shirt is worth a look, too.

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Jack Wolfskin Seamless Wool Long Sleeve: first impressions 

Base layers are an essential item for hiking and winter sports, but they're not all created equally. Some are too heavy, some get too stinky on sweaty pursuits, and others still can't quite ditch the itch of wool. We've been testing the Jack Wolfskin Seamless Wool Long Sleeve on hikes in the Scottish highlands, the Lake District and the English lowlands for the past couple of months and found a lot to love about it.

First off, it's ultra-lightweight and has a precise fit, so it's easy to layer and move in, and it's not too warm if the weather turns mild. The blend of merino wool and polyamide isn't scratchy on the skin and has great thermoregulating properties, keeping you warm and dry if you get sweaty on cold days. It doesn't get stinky quickly, so it's good for a few adventures thanks to the merino content, but the synthetic fabric means it's a little more durable than a straight merino top.

The seamless circular design means that there are no seams on the torso (there are, of course seams on the sleeves) and that may reduce chafing for those who struggle with it. Either way, it makes for a flattering design and has loads of stretch for comfort in movement.

The only real flaws we could find were the lack of thumb holes (though the performance fit means it's easy to layer without them) and it is on the pricey end for a base layer. The quality certainly means you can expect some longevity out of this top, and we love that it's light enough you can roll it up and stuff it in any bag whether you're going backpacking or hopping on a plane for an active adventure.

Jack Wolfskin Seamless Wool Long Sleeve: in the field

I pretty much live in base layers and I'm always looking for ones that I can wear across multiple adventures that keep me warm and dry but aren't too warm or bulky. I've been testing this out for a couple of cold months in the Scottish mountains as well as on some recent adventures down to the Lake District where I went forest bathing and South Downs National Park on a foraging expedition.

Here’s how it performed:

Sizing and fit

I usually wear a small but I was sent an XS by Jack wolfskin and it actually fits quite well, probably because it's so stretchy. I think I probably err on the side of wearing everything a little loose, for comfort, but I think a small would have been perfect for me, so I wouldn't necessarily recommend sizing down.

The fit of this base layer is really flattering, thanks to the circular design and the crew neck keeps a cold draft out without being annoying. Also unlike a lot of similar base layers, the sleeves seem to be the right length and I don't have tons of extra fabric bunched up around my wrists, though it does bunch slightly on the wrist where I wear my watch.

Weight and comfort 

Next to my Black Diamond Long Sleeve, this is the lightest base layer I own, which I really like. Though I do prefer a thicker wool layer during the coldest days, this design is far more versatile, so I can wear it on its own when it's mild and layer up with a fleece when it's cold. I don't even notice I'm wearing it when I have lots of layers on, and it rolls up really small so I didn't even think twice on bringing it along as an extra layer on a recent press trip to the South Downs.

I can't say that I've ever really noticed the seams on a base layer, but this one is certainly comfortable, mostly due to the fact that it's not at all itchy despite the wool content and also the stretch (I was able to wear it for a chilly yoga session during a glamping trip). As I said, I barely notice I'm wearing it, so what could be more comfortable than that?

Thermoregulation and odor protection

Even though adding synthetic fabric to a natural material merino means you jeopardize its capacity to biodegrade, it's hard to deny that the blend offers the best performance when it comes to temperature regulation. I've tested this out on some steep climbs and never felt too warm, so I know it breathes well, wicking away sweat and drying quickly too. That said, it's also enough to keep me warm when it's really cold out and I have a warmer jacket on top.

Synthetic tops get really smelly with a single use, but this one has enough merino that it lasts for a few adventures without needing washed, which means it's lower maintenance and helps balance that sustainability component.

Jack Wolfskin Seamless Wool Long Sleeve: the bottom line

This long sleeve has earned a coveted position in the top three base layers in my drawer and its lightweight performance means it's easy to grab if I want a backup. The lack of thumb holes may be a deterrent for some, though not for me personally, while I do recognize that the price tag won't be for everyone. For a high-performing lightweight style that's a little easier on the wallet, check out the Black Diamond Long Sleeve Rhythm in comparison.

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Inov-8 Graphic T-Shirt: first impressions

With the costs of even the most basic outdoor items seemingly rising inexorably at the moment, it’s refreshing to come across a garment like this hiking T-shirt from British brand inov-8, which has a much more reasonable list price.

Best known for producing reliably excellent trail-running shoes and apparel, in recent years inov-8 has widened its offering to include hiking boots and walking shoes, and the brand has also branched out into trekking trousers and tops. 

But does cheap also leave us cheerful? I’ve been testing the Inov-8 Graphic Tee to see how it compares to the best hiking shirts on the market.

Inov-8 Graphic T-Shirt: design and construction

This is an unfussy and down-to-earth T-shirt, with no collar or neck zip. It’s constructed from a material mix comprised of 50% cotton and 50% modal, with the latter fabric being made from cellulosic fiber sourced from trees, usually beech. It’s often touted as an environmentally friendly fabric because it’s biodegradable (in certain circumstances) and recyclable, but there is some debate about how ecological it really is. (It all comes down to the practices employed by the suppliers of the modal to the brand, for which we don’t have full visibility.)

There is zero debate about the next-to-skin comfort of the material, however, which is undeniably deliciously cool and comfortable. It’s also tough and robust, and will hold its shape well.

On the downside, both cotton and modal absorb much more moisture than synthetic fabrics like polyester, so if you get this garment wet it will weigh you down quite a bit, and will also take ages to dry. Furthermore, unlike other natural materials such as Merino wool and bamboo, cotton offers no thermal properties whatsoever when wet, and can actually make you colder.

Used in the right sort of environment, however, this makes an excellent hiking shirt, climbing T-shirt or running top.

Inov-8 Graphic T-Shirt: on the trails

I’ve been testing this T-shirt while hiking, climbing and running in a wide range of weather conditions and temperatures over the last 12 months, and I ’ve enjoyed using it in all four seasons. Importantly, I’ll caveat that by saying I avoided wearing it in the hills and peaks during the winter, and outdoors in wet and cold conditions generally, because cotton is far from the best material to get caught out in when the elements get grumpy.

In winter I stick to using this T-shirt for trips to the climbing gym and in spring and fall it’s best worn on short walks and trail runs when conditions are definitely dry. But in warmer weather the lovely feel of the material and the relaxed fit of the tee makes it perfect for wearing while out hiking on coastal and countryside trails, or climbing at the crag.

A relatively basic garment, the Graphic Tee doesn’t claim to revolutionize your outdoor experience, it just feels nice to wear, allows you to move completely freely, wicks moisture away from your body when you break a sweat, protects your torso from the wind and the sun, and looks good with a pair of jeans at the pub when you’re enjoying mid- or post-adventure pints.

Oh, and it won’t empty your wallet either – with many base layers (both short and long-sleeved versions) costing around 100 bucks these days, this modest but highly functional tee is available for a fraction of that.

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Smartwool Men's Classic All-Season Merino Base Layer Long Sleeve: first impressions

It’s always nice putting on a new merino garment – the slight initial chill of the material in the morning soon gives way to a protective feel, and the fabric is, in my opinion, unrivalled in its next-to-skin comfort. Nothing else comes anywhere near it. So, suffice to say, I was excited to start testing out the Men's Classic All-Season Merino Base Layer Long Sleeve from Colorado-based merino specialist Smartwool, which is close to 90% merino wool. 

The remainder of the material mix is made up from recycled nylon, which adds strength to the fabric – one of the few weaknesses of merino garments is a tendency to develop holes after a bit of wear and tear, and the addition of a tough synthetic like nylon should help stop this happening, improving the useful life of the top. The fact that it’s recycled nylon is positive, and it’s also worth noting that the merino wool used here has been certified as responsibly sourced, and plant-based eco-friendly dyes have been used to create the selection of funky color options.

With such a high level of wool content, the attributes of this top will be familiar to merino fans: aside from offering luxurious comfort levels (enhanced here by the flatlock seams), it promises to let your body breathe really well during outdoor activities, to wick moisture away when you sweat, to fight off any accumulation of bad odors with its naturally occurring bacteria-busting enzymes and, perhaps most importantly, to help you regulate your temperature across all four seasons.

All these benefits of merino-based garments are well known, so I had high expectations of this top when I started trail testing it to see how it compares with the best base layers on the market.

Smartwool Men's Classic All-Season Merino Base Layer Long Sleeve: design and construction

Somewhat strangely, I can’t see the GSM (grams per square meter, which indicates how thick the fabric is) of this garment anywhere on the Smartwool website or the packaging, but it is noticeably thin. This plays into the all-season style, and merino does have the remarkable ability to help you stay warm when it’s cold outside, and cool when conditions are hot. The thickness of the material of course comes into this, and you will need to combine this particular top with a good mid layer in the form of a decent fleece or puffer jacket in order to remain comfortable in the midst of winter, or at altitude. And while merino is wonderful for all sorts of reasons I have already detailed, it does take some time to dry if you do get it wet, so a reliable waterproof jacket might be required as an outer layer.

In the shoulder seasons of spring and fall, and all through summer, however, this lightweight construction will help you stay shielded from the sun and wind when required, and then provide adequate thermal protection during chilly mornings and evenings at the crag or in camp.

Smartwool describe this garment as having a slim fit. There is no elastane or Lycra content in the fabric, so it doesn’t feel tight or supply any compression, but the thin, lightweight material does hug your contours. On test I actually found the sizing to be quite generous, and the large top I’ve been wearing (my usual size selection) was a tad baggier than I typically like base layers to be – so bear this in mind if you often fall between sizes. 

Smartwool Men's Classic All-Season Merino Base Layer Long Sleeve: on the trails

I've been wearing the Smartwool Men's Classic All-Season Merino Base Layer for several weeks, as winter has segued into spring in England’s soggy south west, while doing dynamic activities ranging from hiking and trail running to cycling and climbing. 

As expected, it feels super soft and smooth next to my skin, and I have experienced zero itchiness or scratchiness. The comfort levels are further improved by the flatlock seams, but one of the features I particularly like about this top is the offset shoulder and side seams, which Smartwool has employed to reduce the risk of rubbing and chafing when you’re wearing it while hauling a hiking backpack, daypack or hydration pack. This is a great touch.

One niggle I do have with this top is that it lacks thumb loops, so the sleeves ride up when you put on a fleece or jacket, and it’s harder to avoid ending up with some exposed skin if you’re wearing it with gloves while hiking, biking, running or skiing. Thumb hooks or loops are such a simple and useful addition to base and midlayers, and I really don’t understand why more brands don’t use them. There is a hang loop on the back of the collar of this top, which can be handy (but it’s definitely not as necessary as thumb loops).

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Smartwool Men's Active Mesh Short Sleeve T-shirt: first impressions

T-shirts are ostensibly simple garments, but with the Smartwool Men's Active Mesh Short Sleeve T-shirt there’s more going on beneath the surface than you may realize. (There’s certainly more going on than I appreciated, until I started looking into why a T would have such a steep price tag.)

As you would expect from any item of clothing from US-based brand Smartwool, the main ingredient in this crew-neck garment is merino wool, and the benefits of this magic material are very well known: it breathes beautifully, wicks moisture away from your sweaty body like a dream, feels absolutely lovely next to your skin and – armed with naturally occurring bacteria-attacking enzymes – it doesn’t start to pong even if you wear it for multiple days in a row while hiking, biking, climbing, camping or any other high-energy activity. All of this makes it a great fabric for use in a top designed for demanding use in the outdoors. 

The downsides are equally well known, and chief among them is merino’s tendency to develop holes and deteriorate over time. This is an unsurprising failure point in an item of clothing made with natural materials, which will eventually biodegrade, but if you’re forking out serious money for a shirt (and this really is an expensive T by any measure), you do want it to last.

And so, with the Active Mesh short-sleeve T, Smartwool have introduced some other harder-wearing fabrics into the mix, namely recycled polyester and Tencel Lyocell, a material made with pulped wood (from sustainable sources).

These tougher fabrics are used to particularly good effect in places of high stress, such as the shoulders (which are prone to friction-related damage if you commonly hike with a backpack or daypack, or use a hydration pack when running or riding). And, not only does this material cocktail make the Active Mesh T more robust than a pure merino wool shirt, the poly content should also improve how quickly the garment dries.

To find out how it performs compared to the best hiking shirts on the market, I put the Smartwool Active Mesh short-sleeve T to the test in the field (and on the trails, and even on the water).

Smartwool Men's Active Mesh Short Sleeve T-shirt: on the trails

A good-looking garment that works with a pair of jeans when you’re socializing as well as performing well on the trails, the Active Mesh short-sleeve T can be worn as a hiking shirt or a running top – or you can use it while kayaking, climbing, cycling, skiing or during any other outdoor sport or activity. With its excellent odor management and highly functional material composition, it’s particularly well suited for multi-day backpacking and bikepacking escapades.

Over the last few weeks I have been wearing this versatile top while hill walking and trail running in Devon, and during an epic day of paddling along a canal that runs along the seam of England and Wales.

Although it’s short-sleeved, I think this T-shirt will work well as a base layer worn beneath a good fleece or puffer jacket between spring and fall, as even during the last gasp of winter I found that it supplied a decent degree of thermal protection to my torso, while not restricting my arm movements at all. During summer, of course, it will perform perfectly as an outer layer, especially because areas such as the shoulders have been toughened up with the use of the lyocell fabric (in the past I have found this to be a real weak spot with other merino tops I’ve worn while carrying a pack).

The styling and sizing are both quite relaxed, and this combined with the soft feel of the merino wool and flat seams makes this T-shirt very comfortable to wear for long periods of time. I was on the water for 10 hours when I wore this top for the very first time, straight out of the (environmentally friendly cardboard) box it arrived in, and after I’d finished kayaking I kept it on for the five-hour drive home because it felt so good. The following day it still smelt new, which is quite an achievement after the sweaty experience I had just put it through.

Similarly, while subsequently wearing it for hikes, bike rides and even runs, I could feasibly have worn it repeatedly before really having to launder it. The mesh elements on the sleeves and back make this T even more breathable than a standard merino top, and add to the comfort levels.

My running activities over the last month have taken place during a particularly soggy February, and the performance of the recycled polyester in the T-shirt has been impressive. It’s less clingy than a pure merino top when it gets damp, and definitely doesn’t hold as much water, get weighed down to the same degree or take as long to dry after you get caught in a downpour.

Overall, while the initial outlay is heavy, this is a top that will serve you well throughout all four seasons and for many years of adventures, so it’s a decent investment.

• How Advnture tests products

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Saxx Roast Master Mid-Weight: first impressions

The first thing I noticed about the Saxx Roast Master Mid-Weight long-sleeved top was the lovely smooth feel of the fabric – which is quite an achievement when you consider that it’s almost 10% wood. Some synthetic base layers have a very plasticky texture, and crackle with static when you put them on. Not, though, this garment from American brand Saxx, which specializes in producing comfortable, functional and technically advanced men’s underwear for use during active pursuits, including adventure sports and outdoor shenanigans.

A midweight base layer, the versatile Roast Master long-sleeved top is part of Saxx’s base layer range, designed for cool-weather use by hikers, bikers, runners, skiers, boarders, paddlers, climbers and campers. The material mix includes recycled synthetics and Tencel lyocell, an eco-friendly fabric where the fiber content is derived from sustainable wood. A small amount of elastane is also used, to provide some stretch and ensure the top won’t inhibit your movements on the hillsides, mountaintops, wild water, snowy slopes or rocky crags. 

At least, that’s what the brand say. I’ve been field-testing the Roast Master long-sleeved top while doing a range of outdoor pursuits over the last six months to see how it performs compared to the best base layers on the market.

Saxx Roast Master Mid-Weight: on the trails and in the hills

I’ve been wearing the Roast Master while out and about on hill walks, day treks, trail running, paddling and climbing adventures in a range of fall, winter and spring conditions. Typically I’ve been wearing it beneath a fleece and/or a waterproof jacket, and occasionally – when the sun was out, or while I was doing something a bit more energetic, like running – I’ve worn it as an outer layer, revelling in the funkiness of the ‘Get Out Camo’ color and pattern on the version I’ve been testing (which resembles ripples on moonlit water).

As I expected I would from the smooth texture of the fabric, I found the Roast Master extremely comfortable to wear right from the outset. It has a lovely next-to-skin feel, and the flat seams are virtually undetectable during use, so you can wear it for long periods of time during active use with no problems whatsoever. However, while I never felt my movement was impacted or restricted by the top, the degree of stretch is not as pronounced as in some base layers I’ve tested.

Also, despite Saxx saying it’s a slim fit garment, I found the Roast Master to be slightly over-generously sized. Bagginess is not something everyone wants in a base layer, and a loose fit can impact how warm an undergarment feels (with air not getting properly trapped between the top and the wearer’s body). Suffice to say, if you generally prefer a body-clinging base layer, choose a size smaller than you usually would. I’m 6ft 1in / 186cm and normally take a large, which is the size I tested, but I think the medium would have performed better.

During energetic activities such as hill clambering and trail running, the material proved itself to be adequately breathable, and it wicked moisture away from my skin well. Being synthetic, it continues to work and provide thermal protection even when you get it damp, and the fabric also dries extremely quickly, so these are all big ticks.

Saxx say this garment has been treated with an anti-odor product to stop it stinking up after repeated use (as synthetic tops are prone to do, unlike merino and bamboo-based clothes), but only time will tell if this works – I’ll report back if people start avoiding me. Like all synthetic clothing, though, I do confidently expect this top to be robust and long lasting.

My main criticism of the Roast Master long-sleeved top is the lack of thumb loops or hoops, which means the sleeves can and do roll up when I pull another layer on. Thumb hoops are such a simple feature to include – and they also allow you to ensure there’s never any exposed skin when you’re wearing winter gloves – it amazes me when brands don’t include them on their base layer tops. Sort it out Saxx.

• How Advnture tests products

Hitting the trails regularly takes more than just finding a route on your favorite navigation app and lacing up your hiking boots. When it comes to mother nature, you’ll be amazed at how much time and thought goes into making sure you’re warm enough, but not too warm, and managing your sweat so that you can cool down, but not get too cool. It’s a tricky world, but fortunately we have amazing fabric technologies like merino wool and fleece to help us navigate it. When it comes to fleece vs wool, however, you might be wondering – which is better?

If you’re a seasoned hiker, it might seem a bit strange to you to compare fleece to wool. After all, according to the unbreakable laws of the hiking layer system, you should be wearing a wool base layer with a fleece jacket over the top, right? Well, sure, when it’s really cold out, this makes for an excellent approach, especially when you complete it with a waterproof shell over the top. 

When it’s not freezing cold, however, you might do away with your mid layer, and these days, we’re seeing super light microfleece tops like the Montane Protium Lite which actually make pretty solid base layers, or even outer layers for mild, dry summer hikes. In the interests of economics and durability, you might be considering replacing your dogged old merino wool base layer and go modern with a microfleece long sleeve top, but concerned about performance.

In this article, we’re not comparing a wool base layer to a heavy fleece jacket; rather, we’re pitting the two fabrics head-to-head when they’re used to create light first layers to help you choose the best defense for your next adventure.

Fleece vs wool: insulation

Obviously, when you’re comparing fleece vs wool, you’re doing so because you’re seeking something to keep you warm on the mountain and by now you probably know that cotton won’t do you any good whatsoever. In all honesty, it’s hard to rate the insulation factor of clothing the way sleeping bags receive a temperature rating. That’s because temperature is a surprisingly subjective experience, and the way clothing performs really depends on what else you’re wearing with it and what you’re doing in it (you can read more about this in our article about why down jackets don’t have temperature ratings).

The good news, however, is that both fleece and wool are built to insulate, and both will keep you warm. One area where wool has a slight edge is that it does continue to keep you warm when it gets wet, so if you’re planning on very rainy treks, that’s worth considering – but with a good waterproof jacket that shouldn’t really factor into things. 

Fleece vs wool: moisture management 

Since we mentioned getting wet, it’s worth mentioning how each fabric responds to moisture, as this will affect your comfort levels. Though wool will repel a light rain for a bit whereas fleece won’t unless it’s treated to do so, this isn’t really a factor when it comes to first layers, because in wet weather you should be wearing waterproofs over the top. How each fabric protects you from your own sweat, however, is important to understand.

Both fleece and wool are breathable, meaning they’re porous fabrics that allow water vapor to pass through. That said, not all fleece is moisture-wicking, but if you’re looking at a garment that’s designed to be a first layer, make sure the lining is made using brushed fleece in a grid pattern and it should be good for aerobic activities. If your fleece does get soaked – say under the armpits after a steep climb – then it will dry in a flash.

Any wool base layer will be designed to be both breathable and great at pulling sweat away from your skin – but remember it will stay wet for longer.

Fleece vs wool: comfort

One of the reasons fleece was considered such a great alternative to wool when it was first invented as Polartec in 1979 is because it does away with the scratchy wool feel that many people can’t stand. It’s true that lots of people who hate touching regular wool can handle merino wool, but for the most sensitive wearers, even that is too itchy. In that regard, fleece really shouldn’t cause any wearer any discomfort so long as you choose the right size.

Fleece vs wool: weight

The weight of a wool base layer versus a microfleece top really depends on the construction, so this is a category where it’s fair to say it’s a tie. A look back at some of the base layers I’ve tested in the last couple of years shows that the lightest was the Black Diamond Long Sleeve Rhythm t-shirt, which is made from merino wool and really thin with no zips to add grams. However, one of the heaviest was the Helly Hansen LIFA Merino Midweight Crew, which is also largely merino wool but uses a two-layer construction. Basically, the weight of your base layer will depend on its thickness and whether it has any zips.

Fleece vs wool: sustainability and ethics

If you’re shopping for any outdoor gear, questions of sustainability and ethics should always be at the forefront of your considerations – after all, you want to have a planet to keep exploring.

Fleece is a synthetic material so it’s worse for the environment to produce and it won’t biodegrade when it gets to the landfill. That said, a good fleece that’s well looked after could last you the rest of your life, and more and more fleece is being made using recycled materials these days, like the Helly Hansen Daybreaker which is 100 percent recycled.

Merino wool can be produced really sustainably, and it’s biodegradable, so on the surface of things it’s a better choice for the environment, but it’s still important to make sure the wool you’re buying is produced in a cruelty-free and ethical manner. Always read the labels and do your research into the brands you’re buying from.

Fleece vs wool: the stink factor

This is one area where we can easily crown a winner. While many fleece tops can become absolutely repellent after a single sweat session, wool is known for being able to stand multiple wears without getting smelly. Scientists have varying theories on why wool is so odor-resistant, but if you want a garment that you can wear loads without washing, go for wool.

Fleece vs wool: cost and durability

 When it comes to matters of cost and durability, fleece is pretty much always going to be both cheaper and more hard-wearing, whereas wool is generally more expensive and doesn’t last as long, often developing holes with frequent use and is prone to shrinkage.  

That said, fleece requires more washing than wool and is subject to pilling, which levels the playing field somewhat. With good care, you should be able to get a good amount of use out of any good quality garment, so read our guides on how to wash a fleece jacket without ruining it and how to care for your merino wool gear.

Fleece vs wool: the verdict

As you can probably see, there isn’t a clear winner when it comes to measuring up a microfleece top against a wool base layer for hiking. Both will keep you warm and, if well-designed, should be breathable and wick sweat. Some factors that might have you erring towards fleece are its lack of itchiness, quick-drying capabilities, lower cost and better durability, however wool boasts excellent odor-control, requires less washing, and is more planet-friendly.

• Fleece vs down jacket: which do you need?

Columbia Tunnel Springs Wool Crew Baselayer: first impressions

When you’re looking for a base layer, you want something that will keep you warm without overheating, wick sweat when your activity gains intensity and dry reasonably quickly so you’re not shivering out in the cold wearing a wet top at the summit. Some base layers have extra bells and whistles like zips and hoods, but with the Tunnel Springs Wool Crew, Columbia has relied on a straightforward approach and it’s paid off.

This base layer is made using a blend of wool and synthetic Lyocell, so it boasts temperature-regulating and odor-control properties of the former but is more durable and quick drying thanks to the latter. It’s light enough to wear in a range of temperatures and across different activities, providing warmth on chilly days when paired with a fleece and shell, but can also make a running top in cold weather or be worn on its own for mild hiking days.

Handy thumb loops make it easy to layer or wear with gloves. The fabric doesn’t really feel like wool, it's a bit like a textured cotton in feel. For the most sensitive skin, it could be a little itchy, but in general we think most people would be surprised to discover it’s wool. It doesn’t have any added stretch, but there’s plenty of pliability for all sorts of movement and the lack of elastane adds to the durability of this garment. Overall, this is a timeless-looking first layer that you can comfortably use across all sorts of activities.

Columbia Tunnel Springs Wool Crew Baselayer: in the field 

As an avid hiker, trail runner, skier, climber and everything outdoorer, I can’t really ever have enough base layers – unless they’re itchy or too hot that is. In a base layer, I look for something with some wool content that is breathable and quick drying and helps me stay warm when it’s cold.

I got to test this base layer out on a hut hiking trip to the French Alps this fall with Columbia, wearing it during the colder night hikes. Since I’ve returned to Scotland, I’ve been wearing it a lot, on hikes up Munros and for about five days straight on family walking holiday.

Here’s how it performed:  

Size and fit 

I am a size small and tested a small and it fits true to size. It sits close to the skin but without any elastane, it’s not figure hugging. In general, you need base layers to lie against the skin to wick moisture, but while this isn't skin tight it seems to be close enough to do the job.

Temperature regulation and breathability

I’ve tested base layers that are really warm, but this one is light enough that it makes a good first layer while being versatile across different activities. So far I’ve mostly worn it for hiking though I’ve also worn it for some cold trail runs and been quite happy. The wool/synthetic blend means it’s both breathable when I do get sweaty, and thankfully it’s really quick drying too which makes it a good choice for high intensity adventures.

Comfort 

This is neither the softest nor the itchiest base layer in my closet. When I first received it, I actually didn’t realize it was wool, which is unusual. For a moment, I thought they had sent me a cotton base layer, which would be mad, but it feels almost like coarse cotton rather than wool. I imagine those with sensitive skin would be able to tell, but for me it only has the slightest itch factor. That said, it could be softer against the skin, but I can happily wear it all day.

You might think the lack of elastane would make this less comfortable, but the fabric naturally has enough give and the fit is right so I’ve been able to do yoga wearing it no problem.

Odor control and durability

Synthetic materials tend to get stinky while wool doesn’t, and this top manages to harness more of the properties of wool in that department. As I mentioned, I wore it for five days straight without needing to wash it – just airing it out was enough between uses.

Wool isn’t always the most durable, especially when you don’t take good care of it, but blending it with synthetic fabric and skipping the elastane bodes well for longevity, plus there’s no zip to fail. The odor-control also cuts down on how often it needs washed, which helps no end.

Columbia Tunnel Springs Wool Crew Baselayer: the bottom line

If you’re seeking a versatile first layer that boasts some of the best properties of wool but is reinforced with synthetic fabric, check out this classic-looking, lightweight and effective base layer.

• How Advnture tests products

ThruDark Oryon Delta Long Sleeve T-Shirt: first impressions

ThruDark is a British brand whose founders were members of the United Kingdom’s Special Forces. Their experience of extreme climates and challenging situations has lead them to create an uncompromising product range, with everything from flannel shirts and caps to high performance outdoor apparel.

Don’t expect bright flamboyant designs – ThruDark’s kit is unapologetically macho in terms of aesthetic, with metallic color schemes, the occasional skull and the ever-present trident logo, hinting at a sort of mythical strength and power. Employing quality components, fabrics and materials, their clothing is designed to ‘endeavour through adversity’.

Its Oryon base layers, available as either short- or long-sleeved, make use of Polartec’s high breathable Delta fabric, which is designed to keep the wearer cool during activity in hot climes. The fabric is enhanced with Polartec’s Fresh Face, a natural and biodegradable odor reducer that’s a more sustainable alternative to traditional fabric fresheners.

I was keen to see how ThruDark's design and Polartec's innovative fabric fared when faced with the mountainous backcountry and was delighted to get the opportunity to find out earlier this year.

The Oryon (available to buy direct from ThurDark) looks and feels premium, with little design touches, such as the understated trident insignia on the left breast and below the collar or the small Union Jack flag tab – a touch that'll undoubtedly please patriotic Brits. To wear, the top's textured fabric is soft and feels pleasant against the skin.

With a list price of $140 (£110 in the UK), it’s more expensive than most hiking tops, though some merino options will set you back more. Nevertheless, I could immediately tell this was no bog-standard base layer.

The main plus points of Polartec's Delta fabric are its moisture-wicking and fast-drying capabilities, along with what Polartec call its ‘metabolic cooling’ qualities. These benefits are achieved thanks to a combination of hydrophobic (water repelling) and hydrophilic (water absorbing) fibers. Turn the t-shirt inside out and look closely and you’ll notice a matrix of touch-points, which sit against the skin, ever so slightly raising the majority of the fabric.

The fibers work with your sweat by first drawing perspiration away and then distributing it, holding moisture close to the skin. Hot air flowing through the trapped moisture is cooled, enhancing your body’s natural cooling system. This design has numerous advantages: it increases ventilation, allows for faster moisture dispersal and also avoids that clingy sensation that often occurs when working up a sweat.

As well as Delta’s cooling properties, the fabric is also treated with Polartec’s Fresh Face, a biodegradable, plant-based odor reducer. When launched earlier in 2023, the Oryon was one of the first products in the world to feature this innovation, along with 66 North’s Grettir tops. Derived from non-GMO mint oil plant extract, Fresh Face was tested comprehensively against traditional, metal-based additives over 50 wash cycles and was found to more than hold its own. In short, it means the Oryon not only repels unpleasant odors but is also kinder to the environment.

Two relatively large, zippered chest pockets give interesting storage options. I’m not overly convinced by them, both from a practical and an aesthetic point of view. Due to the thinness of the fabric, it’s a little uncomfortable putting anything at all substantial in there. I also think that the short-sleeved version of the Oryon, which doesn’t have pockets, looks all the better for it. Though beauty is obviously in the eye of the beholder, so you'd be within your rights to disagree.

The pockets are also mesh-lined on the inside, creating two layers, which are obviously less breathable than one. Benefits of the Delta fabric’s touch-point design are also wasted on the inside of the pocket, rather than being used against the skin below the pockets. On the plus side, the mesh is breathable. I also get the sense I’m nit-picking a tad here, which is what us reviewers end up doing when there's very little else wrong with a garment.

Interestingly, the apparel in the Oryon range, along with ThruDark’s Rōnin range, are made in Ukraine. ThruDark say that ‘every garment produced is a testament to the dedication of those continuing to endeavour in the face of such great adversity afflicting their homeland.’ This approach is certainly laudable.

ThruDark Oryon Delta Long Sleeve T-Shirt: on the trails

I put the Oryon to the test on strenuous hikes in Bannau Brycheiniog (the Brecon Beacons), Eryri (Snowdonia) and the Lake District national parks, with some pretty adverse weather conditions thrown in. For the entire stint in the Lake District, it remained firmly as a base layer, hidden beneath a fleece and waterproof outer.

I found it to be wonderfully comfortable as both a base layer or as a standalone on warmer days. It’s not as soft as a bamboo top, though its textured inner fabric feels lovely against the skin and it doesn't suffer from the slight itchiness of a Merino base. It’s also neither clingy nor baggy, with a nice fit that worked well under additional layers. I can also report that the Fresh Face odor-reducing treatment was effective, even after multiple wears and wash cycles.

The front half-zip came into its own on long ascents, allowing me to dump heat effectively when required. On such ascents, lesser base layers tend to cling when working up a sweat. Not so the Oryon, underlining the clever design of the Polartec Delta fabric’s touch-points.

As well as this, I really liked wearing it in cooler climes too. It seems to insulate well in dry conditions, trapping warm air between between my body and the fabric, while its long sleeves make it a good shout for wintry adventures. It doesn’t have thumb loops, but the tight-ish fit of the arms meant that I never noticed it riding up when I added a mid-layer.

This wasn't the first collaboration between ThruDark and Polartec that I've tested for Advnture. I had an issue with the placement and heftiness of some of the seams on ThruDark’s Centurion Alpine Jacket but I’m glad to say I had no such qualms with the subtle seams on the Oryon.

All in all, this is a great base layer that's hard to pick fault with and one that I'll continue reaching for throughout the seasons.

• How Advnture tests products

Merino wool, you may have heard, is a miracle fabric for hiking and other outdoor activities. It’s biodegradable, doesn’t get smelly for ages even with heavy use and most importantly, it continues to insulate when wet. That means if you get sweaty on a hike, or your waterproof jacket can’t hold up to a deluge and wets out, you won’t freeze. For these reasons, it’s a popular component in base layers and hiking socks where you often encounter cold and wet conditions. But what about hot and dry conditions? Does it make any sense then?

I’ll admit to being a merino wool-wearer in all conditions. When it’s freezing out, my first line of defense is a long sleeved base layer like my EDZ merino top which is extremely toasty. When things warm up, I basically just lose the sleeves and wear something a bit thinner and looser, but made of the same ingredients, such as my IBEX Springbok Tee. 

But if you tend to run hot, or adventure in warm conditions, I can certainly understand why you might question the wisdom of wearing wool. Read on to understand how merino wool functions in hot conditions, and whether it’s right for you.

How can wool cool you down when it heats you up?

Wool is well-known for its insulating properties, so if you’re hiking someplace where you’re not expecting low temperatures, you might really be asking yourself whether it makes any sense. If you’re spending a week hiking in Moab in September, for example, do you really want the insulating properties of wool during the day? Wouldn’t you be better off in bamboo or even a loose-weave synthetic fabric that doesn’t retain so much body heat?

Manufacturers of merino wool clothing will definitely push the point that the material isn’t just insulating – it’s thermoregulating. That’s a fancy term for something that keeps you warm when it’s cold out but also helps you cool off when it’s warm, and it’s not untrue that merino wool bears these properties.

How can wool cool you down, you ask, when it also heats you up? Well, merino wool is breathable, meaning it allows heat and vapor to escape when you hit that steep section of the trail and start to sweat. It is also moisture-wicking, which means that it draws sweat off your skin and that’s an essential part of how your body’s cooling mechanism works (if the sweat stays on your skin, you don’t cool off).

So in that regard, yes, merino wool really can help keep you cool under certain conditions. That said, however, it all really comes down to your physiology, your unique temperature tolerance levels and perhaps even the aerobic intensity of what you’re doing. 

Can I wear merino wool in hot weather?

I don’t sweat a lot and I don’t mind getting a little warm, but I hate being cold, so I often wear a merino wool T-shirt like my Icebreaker Cool-Lite Amplify Short Sleeve for summer adventures. However, when it’s really warm (usually when I’m indoors on a hot plane or train), I definitely can start to feel a little prickly in merino wool. As long as there’s a breeze and I’m outdoors, however, it’s usually fine.

My friend Jon, a keen mountain biker and outdoors journalist, loves merino wool for cold weather adventures and daily use, but admits he finds it too warm for high energy activities in warm weather. Unlike me, he runs hot (he wears shorts from about March to November) and sweats a fair amount when he is exercising, and for him, that’s part of the problem.

Despite being relatively fast drying, merino wool definitely holds onto moisture more than synthetic fabrics. This doesn't matter when it’s cold, because it still insulates, and when it’s very hot, it can kind of keep you cool by providing a wet layer, kind of like a damp towel on your forehead after a hot yoga class. But it doesn’t necessarily feel great to someone like Jon, who understandably doesn’t want to be wearing the equivalent of a damp towel on a warm mountain bike ride.

It also depends on the thickness, or weight, or the garment. My EDZ base layer is fairly thick, at 200gsm, so it’s seriously toasty and I’m pretty sure I’d die if I wore it on a warm weather hike. My Icebreaker tee, in comparison, is much thinner and has mesh panels under the arms, so I had no issues wearing it on a pretty hot thru-hike on the West Highland Way last year. Be careful, though, in buying ultra thin merino clothing as this can deteriorate quite quickly with heavy use.

Finally, whether the garment is pure wool or blended with other fabrics will affect its performance, so it’s a good idea to read the label before dancing off into the desert. A top that’s a blend of merino and synthetic, like my Icebreaker top which also uses nylon and TENCEL, might actually be better for those who tend to suffer in the heat, though it may lose some of the qualities we love merino for.

So the long and the short of it is, it all depends. If you’ve never worn merino wool in warm weather, you’ll most likely find it a lot more comfortable than you think, and the fact that it doesn’t get very smelly is a big plus in warm weather, but the truth is you’ll probably need to try it out for yourself. If you find that even a lighter merino wool layer is too hot when the weather is warm, try clothing made using synthetic material or bamboo instead.

• Best women's hiking tops

Smartwool Women’s Classic All-Season Merino Base Layer: first impressions

It’s not an easy task to achieve high ethical production standards and also deliver top-end technical functionality when you’re making outdoor apparel from animal-sourced fabrics, but I think the Smartwool Women’s Classic All-Season Merino Base Layer delivers on both fronts. This high-performing, super comfortable base layer proudly boasts ZQ certification, which means the manufacturing process conforms to strict standards of animal welfare, environmental sustainability, fiber quality, traceability plus overall social responsibility.

The top’s Tencel Lyocell fibers are made from composite recycled cellulose, making the garment lightweight and super comfortable for a range of different active sports. Temperature regulation, odor resistance and moisture management are all key reasons why many people opt for Merino wool – but with this top users don’t suffer with the dampness that you sometimes experience with wool, thanks to this high-performing, recycled cellulose fiber. It feels nice against the skin, helps minimize awkward sweat patches and makes the garment ideal for wear in-between temperature fluctuations. I reckon this is a product for all seasons. 

However, I did feel that the sizing was somewhat generous, with extra room on the waist and arm length; the small top I was testing felt more like a size 12 – so this is worth bearing in mind if you’re after a more fitted top. 

Smartwool Women’s Classic All-Season Merino Base Layer: on the trails

I tested the Smartwool Women’s Classic All-Season Merino Base Layer on the fells of the Peak District. While I was walking, I felt it managed to balance the warmth generated from long uphill hikes against the chilly winter breeze, yet the powerful wicking performance of Smartwool’s ultralight fabric kept that icky “damp wool” feeling away. 

Fit

First things first – the Smartwool Women’s Classic All-Season Merino Base Layer was a lot bigger than I expected it to be. Despite ordering a Small, it was large across my shoulders, back length and arms, and felt more like a size 12 than a size 10. This seemed to chime with other buyers’ comments on Smartwool’s website too, so do factor this in. 

However, this needn’t be perceived as negative – I rather embraced the baggier, looser fit. It gave me the option to wear the garment over the top of other layers, which meant the product had extra versatility – I have enjoyed wearing it as a mid layer after finishing walks, and swapping it out when reaching summits on spring days. I do suggest sizing down, though, if you’re after a more true-to-fit base layer experience.

Comfort

Effective thermos-regulation and non-clingy sizing made this top an ideal product for those slightly warmer winter days. Far too often I make the mistake of starting a day in the hills by dressing for the weather at the edge of a breezy car park, only to find myself quickly getting hot and sweaty, de-layering and then rapidly cooling down because of a damp base layer (see also: Hiking layers: everything you need to know to keep yourself warm in all conditions). Yet on hikes up to Derwent Edge, the clever product composition meant I could happily keep this Smartwool top on all day, sometimes wearing it as a mid layer over other base layers. 

Materials & Care

Merino often wears well, then suffers in the heat and beat of a frantic washing machine drum, leading to unsightly holes appearing in the material. With the added Tencel, this top can be washed like a standard wool item on a cold and gentle cycle, though if you’re nervous about shrinkage, you can hand wash it – which can be a faff, but it helps extend the product’s life.

I’ve owned many Merino layers that have experienced a fair bit of abuse. Although I haven’t had this one for a decade, like my other wool base layers, I’m keen to prolong the life of the item, and make sure it can be worn over and over. As Merino wool can be washed less and aired to keep it smelling fresh, I’m excited to see how the quality of the product lasts being worn more often all year round. 

Design

The design is super minimalist, with just a small Smartwool logo and trim. I like that the top is super light, thanks to having no zip. I also love the texture of the Merino-Tencel material, which still feels like wool, but is highly breathable and comfortable against the skin.

With the larger-than-expected sizing, I found I could just pull the long sleeves up when I was walking up hills. The product does not have thumb loops, yet I felt the top performed well enough without them, and this wasn’t a feature fault that felt super important to me, as it has a more “casual” style than most base layers. 

Price

Being a high-quality garment, the Smartwool Women’s Classic All-Season Merino Base Layer comes with a fairly steep price tag, but its ultralight weight and all-year-round functionality makes it a worthy addition to your outdoor kit cupboard. 

• How Advnture tests products

Columbia Silver Ridge: first impressions

Made entirely from recycled polyester, and available in six sensational, trail-cross, plaid-patterned colors, the Columbia Silver Ridge is full of features for the summer hiker, including a large vent on the back panel that lets in fresh air when you’re walking in hot weather and puts it right up there with the best hiking shirts around.

Offering excellent protection from the sun, the material itself has a rating of UPF 50 and the collar can be put up to shield the back of your neck, minimizing the risk of serious heat stroke. The Silver Ridge is long at the rear, which stops it riding up when you wear a hiking backpack, protecting your lower back from the sun.

The cuffs and main front section are fastened with buttons, but the top two are replaced with snap holders that can easily be popped open when you need some extra air to get in or, conversely, popped shut to keep the breeze out. The sleeves can be rolled up to let the sun on your forearms, and a pair of straps with snap holders pop on to an attachment point on the bicep area to keep things tidy and in place. 

There are two useful pockets, ideal for stashing a credit card or some cash – one that shuts with a popper (on the right side of your chest) and another that has a side opening and a velcro fastener (on the left).

Columbia Silver Ridge: on the trails

I’ve been wearing the Columbia Silver Ridge plaid shirt during a series of mid-summer walking expeditions that have taken me through the countryside and also on some urban trails. 

The fit and next-to-skin feel of the shirt is fantastic – it’s both comfortable and cooling to wear on warm days, and the back vent works really well (even when wearing a daypack). The ability to pop the top two buttons open in seconds means I can get rid of extra heat very quickly when walking up steep hills, and I like the fact that rolled-up sleeves can be kept neatly in place, and aren’t left flapping around. Personally, I think poppers on the cuffs would also make sense, making it quicker and easier to adjust the sleeves.

The long-cut back effectively prevents the shirt riding up when I’m walking with a pack on, which stops the small of my back getting sunburnt, but a tiny bit of extra padding on the shoulders would help stop backpacks rubbing my shoulders over time, and improves the longevity of the shirt.

The Silver Ridge wicks moisture away very effectively, but being thin and lightweight (by design) it doesn’t offer too much in the way of thermal protection. Also, since it’s made completely from synthetic material (albeit recycled polyester) it might accumulate a little bit of odor over time.

Overall, this is a very versatile, great-looking shirt that can definitely be comfortably worn both out on the trails and also in the pub garden at the end of the day – or anywhere, really. It looks as smart as it is fully functional.

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IBEX Springbok Tee: first impressions

The IBEX Springbok Tee is a hiking top (or running top, you take your pick) that harnesses the amazing moisture-wicking qualities of merino wool when you’re working up a sweat and blends them with Tencel to create a nice, soft top against the skin. They’ve also included a little nylon to increase the shirt’s durability. The result is a highly comfortable, breathable and fast drying top that’s great for summer hiking and trail running, but can just as easily be your first layer come the winter months.

The scoop neck and flattering fit of this T-shirt are simple enough, but it’s also built for performance with flatlock seams on the shoulders that are brought forward to prevent chafing if you’re wearing it with a backpack and gusseted underarms for optimal range of motion when you’re pulling off your fleece, scrambling or taking your pack on and off. You can stay cool and dry for hours in this shirt, and if you get sweaty and things cool off, it will keep you warm. You can also expect multiple uses out of it without having to wash it, which is good because it’s a cold wash-only shirt. It’s definitely on the pricey end for a T-shirt, but you’re paying for the high standards of merino wool and a very versatile shirt.

IBEX Springbok Tee: in the field

I love merino wool best of all natural fabrics for my outdoor adventures, so I wasn’t shy about saying yes when I was offered the chance to test out this shirt. That said, when it arrived, it looked so simple I was a little worried it would be difficult to talk about it in technical terms. Fortunately, I had nothing to worry about. I’ve been wearing it for weeks on a couple of train runs and a lot of hikes and I’ve even slept in it once or twice.

Here’s how it performed:

Sizing and fit 

This fits true to size. I tested a small and think it has just enough room to be flattering and not catch anywhere but it’s not so big as to flap around or make it difficult to layer over or tuck in. It has a nice scoop neck, the sleeves are long enough to give a little sun protection, and it’s the perfect length that I can either tuck it in or leave it loose.

Comfort and breathability

On its own, merino wool isn’t as soft as everyone might have you believe, but combined with Tencel, another cellulose-based fabric, it feels really nice against my skin. There are small details, too like bringing the shoulder seams forward and flatlock seams that mean there’s no rubbing or chafing.

The fabric blend combined with the fit mean it’s a really good choice for warm hikes. Of course, the back gets sweaty when I’m wearing my backpack, but it dries quickly when my pack comes off and because of the wool, keeps me warm if it’s cooler out even when it’s a bit wet.

Odor control

One of my favorite aspects of merino wool is the no-stink factor. Partly as an experiment and partly out of laziness, I’ve worn this for several weeks now without washing it (not every day, but for many adventures). Today if I sniff the armpits, they are finally a bit smelly but I’d still wear it again tomorrow in a pinch. In my mind, this increases the already sustainable merits of a shirt made with natural materials because then it requires less washing. That’s also a good thing because it’s cold wash only.

Versatility 

What’s really great about this shirt is its versatility. It’s great as a hiking shirt but I’ve also found it really comfortable for trail running, and more me than the super sporty racerback tops out there. It’s also adequate as a base layer for cooler hiking or camping, and in fact when I wore it backpacking recently on the isle of Bute, I loved layering it over a long sleeved base layer for the cool mornings and evenings, and on it’s own in the heat of the day.

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The North Face Bolt Tech T-shirt: first impressions 

As part of its technical hike collection, the North Face has delivered a straightforward, but high performing hiking top in the Bolt Tech T-shirt. Made from a polyester knit, this top is excellent at managing moisture when you’re on a sweaty hike and dries in a flash. The perforated back enhances the breathability and helps you to stay cool and dry when you’re wearing a backpack.

The slim fit of this T-shirt is flattering and also means it’s easy to tuck into your hiking shorts or layer under a mid layer if you’re out on the trail before things warm up. The rounded neck provides decent sun coverage and they’ve relied on goot tailoring rather than loads of stretch to ensure this fits comfortably and secures good durability. Like all synthetic fabrics, it gets stinky after just one sweaty hike, but it may be a small trade-off if you’re looking for a high performing top you can wear all summer long.

The North Face Bolt Tech T-shirt: in the field 

To be honest, I don’t always love reviewing T-shirts for hiking because, let’s face it, how technical can a T-shirt really be? Well in this case, I found that this hiking top really held up well to the demands of sweaty hikes around the Arrochar Alps and while it’s sportier than I prefer, I found a lot to like about it.

Here’s how it performed:

Sizing and fit 

I tested a small and it fits true to size. It has a slim fit, and no stretch added, so definitely don’t size down. If you prefer a little room, you could size up, but I thought the fit, combined with the blocky color design, was both flattering and easy to tuck into my hiking pants. 

Comfort

 Even though it doesn’t have any added stretch, this top is really comfortable with smooth fabric and a good cut that doesn’t chafe anywhere or restrict my movements. 

Breathability

Though there are some things I don’t love about The North Face’s gear over the last couple of years (specifically, the colors, patterns and how urban everything looks) one thing they’ve done really well is come up with garments that are extraordinary at wicking away sweat and dry instantly, or as close to as possible. This shirt just breathes with me when I’m out in the hills, and when it does get damp it’s dry again in no time. If you’re looking for a summer hiking top or tend to sweat a lot, this top is definitely worth a look. 

Durability and odor control

Because there’s no elastane in this top, I expect it to hold up well against lots of wear and washing. It’s made using all synthetic materials, so needless to say it went right in the laundry basket after the first use, but until they invent a real way to control odor in synthetic fabrics, that’s going to be true for any such top. 

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Montane Protium Lite Pull On: first impressions 

In this top, Montane have merged all the best qualities of a fleece with a base layer. It has the exceptional warmth and softness you expect from a fleece when worn on a cold hike, but the super light weight and active fit mean that you can easily wear it for fast adventures. It’s breathable when you’re moving fast and super stretchy for scrambling and rock climbing. 

The outside of this high-neck, half zip top appears like a smooth synthetic base layer, but on the inside you’ll find brushed grid fleece which is warm, soft and moisture-wicking. This also means your favorite top doesn’t end up with annoying pilling where your backpack straps rub. Flatlock seams mean you can happily wear this with nothing underneath, but it has a snug enough fit to layer a jacket on top. It lacks thumb holes, if you like those for added warmth, but other than that we really can’t find anything to complain about. 

Montane Protium Lite Pull On: in the field 

Montane calls this a fleece, which to me conjures up a substantially bulkier, cozier mid layer, so I was surprised to receive this and discover it’s really a base layer, in my opinion, made using fleece. I’ve been wearing it on some chilly spring hikes in Scotland over the last month and really like the innovative approach. The only hair I can find to split is that it doesn't have thumb holes, which isn't really a problem for me anyway.

Here’s how it performed:

Sizing and fit

This fits true-to-size (I tested a small, as usual) and has a slim, but not skin tight fit, which is why I’m classifying it as a base layer. I easily could wear a tank top underneath it on a warm summer day, though I haven’t yet. All this means I can wear it on its own when it’s mild and layer over it when it’s cold. 

Comfort

This base layer has a barely there feel, which I really enjoy. Basically, each time I’ve worn it, I haven’t noticed I’m wearing it, which is just what I want. The brushed fleece is soft against my skin and there’s no rubbing. 

Temperature regulation and breathability 

I’ve worn this on a few quite cold days and been glad for the extra warmth the fleece provides. That said, the breathability has proven to be quite good for milder days, too. 

Weight and packability

It’s as light as any base layer I own, though doesn’t roll up quite as small as my typical merino wool layers because, being fleece, it is a little thicker (you just don’t notice because it’s so light). 

Odor control and durability 

Like all synthetic fabrics, the armpits do get a bit smelly but only after a couple of hikes, which feels like progress. No signs of wear and tear after a couple of washes and wearing it with my backpack. 

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Arc'teryx Rho Hybrid Half Zip base layer: first impressions

The Arc'teryx Rho Hybrid Half Zip base layer (available to buy direct from Arc'teryx) could be a sample illustration in the Outdoor 101 text book for the ideal base layer. Outdoor 101 teaches that the key to staying dry and comfortable in the great outdoors, especially in cold weather, is good layering – and that starts with a reliable base layer. Basically, you’re looking for great next-to-skin comfort, a decent level of insulation and good moisture-wicking performance. A fairly close fit is also important if you really want to maximize the benefits of your base layer. Lastly, good all-round coverage will help to keep your neck, wrists and lower back warm, even during dynamic activity – whether you’re skiing, hiking or climbing.

Sounds simple, but finding a base layer that nails all those requirements isn’t always so easy. Traditionally, your choices have been to go with either a synthetic fabric – typically polyester or polypropylene – or a natural fiber, usually wool. Wool is known for its ability to move moisture and regulate temperature, as well as its natural anti-bacterial properties that help to ward off body odor. Unfortunately, some find it itchy. Softer and finer wools like Merino help in this regard, but they need lots of care and even then, are prone to abrasion. Synthetics, on the other hand, wick even faster than wool, feel soft and smooth against the skin, yet offer good durability too. Their major downside is their tendency to smell, especially after prolonged use.

With the Rho Hybrid, Arc’teryx have attempted to give you the best of both worlds by using a combination of natural and synthetic fibers. The main fabric is their Phasic AR II, a midweight polyester that has been treated with silver ions to neutralize body odor. But there are also zoned panels under the arms made from a blend of natural Merino wool and hard-wearing nylon. Together, you should get great wicking performance, comfort and warmth, without any unpleasant bodily odor.

Arc'teryx Rho Hybrid Half Zip base layer: in the field

This is an intelligently designed base layer that also happens to have one of the best fits of any long-sleeved technical tee I’ve tested. It has plenty of length in the arms and torso (even for a six foot plus hiker), plus a standup collar that does a great job of preventing chills from creeping down your neck. The cut is trim enough to feel cosy without being skin-tight, unlike a lot of other compression-style winter layers out there. The deep neck zip is a great way to dump a little extra heat if you’re working hard uphill too. 

The fabric is soft and comfortable, with very thin, flatlock seams to avoid irritation. The merrow stitching also resists snags a lot better than conventional flatlock stitching, which is a plus for durability. Another bonus is that the fabric is sleek without being shiny, so it slides easily under a mid layer fleece or puffy.

In terms of performance, the hybrid design does its job really well. I’ve worn this layer for multiple days straight, even sleeping in it whilst wild camping in the mountains of North Wales, and it’s stayed surprisingly fresh. It wicks superbly, and the wool underarm panels generally stop things from getting too damp or sticky.

It’s a mid-range layer in terms of overall warmth, which offers plenty of versatility for variable temperatures and conditions. I tend to run hot, rarely wearing heavyweight base layers even in winter, so this is great for use through fall, winter and spring – though it’s a little too warm for summer wear (but then, most people would switch to a lighter, short-sleeved technical tee in those months anyway).

The only minor niggle I have is that the sleeves lack thumb loops. This is a matter of personal preference, but for winter use I generally like to ensure my sleeves are pulled in under gloves and jacket cuffs. On the other hand, the sleeves of the Rho are fairly long and not at all baggy, so it’s not a major issue.

As with all Arc’teryx kit, the price is pretty high. But a base layer is such an important element of your outdoor clothing system that I’d suggest it’s money well spent – in fact, it’s probably worth saving £50 on the price of your waterproof jacket or mid layer and putting it towards a good base layer, like this one. Think about it this way: much of the time, that expensive down jacket or Gore-Tex shell will be stuffed away in your pack. But when was the last time you headed out without a tee? 

All in all, this has quickly become a favorite bit of kit, and it is the top I now tend to pull on whenever I head out on a hike in the hills. It’s a little too soon to judge durability, but so far it shows no signs of wear, and has been through the laundry a few times without losing its shape or showing any pilling.

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Helly Hansen LIFA Merino Midweight Crew Base Layer: first impressions 

In this high performing base layer, Helly Hansen have built upon the already admirable properties of merino wool, which if you don’t know is quick drying, breathable and wicks away sweat when you’re adventuring in cold weather. By essentially creating a two-layer base layer, the merino wool acts like a shell while the layer that touches your skin is non-itchy polypropylene which means even those of you with the most sensitive skin can benefit from the warmth and protection of this base layer. 

This base layer doesn’t have any added elastic fabric, but it’s naturally stretchy enough for all activities and is carefully designed to sit close to the skin the way base layers should, and is easy to layer your fleece jacket on top of. Stripey sleeves give the garment a slightly retro vibe, but the beauty is really in its performance. You can wear this on frigid ski days in the backcountry or sailing in high seas, get soaked and still stay warm and be dry soon after. Priced in the middle of the range, we think it’s excellent value for money. 

Helly Hansen LIFA Merino Midweight Crew Base Layer: in the field 

In three months, I’ve tested this base layer under the following conditions: cold-weather hiking in Scotland, -19°C skiing in Switzerland, sailing the high seas in south Wales and trail running during an extreme cold snap on the West Highland Way. So, I might not be an expert in hiking, skiing, sailing or running, but I think I’m an expert in how well this base layer performs in extreme conditions and I think it’s fantastic.

Here’s how performed:

Fit and comfort

This base layer runs a little on the large side and because they haven’t added a stretchy fabric like elastane, it’s not as figure hugging as some of my other base layers. That said, it sits comfortably next to my skin and the lack of stretch means it’s more durable than some of my other tops. I prefer the fit of it in my normal size, but if you’re on the small end of your size, you might consider sizing down.

What makes it really comfortable is the two-layer construction, so the part that’s next to my skin isn’t itchy wool, and the flatlock seams mean no annoying rubbing anywhere. It's perfectly comfortable under a running jacket.

Though it isn’t super stretchy, I haven’t deducted any points there because it truly doesn’t restrict my movements at all. I’ve even done yoga wearing it, so unless you’re planning on doing something that requires more range of motion than Wheel Pose, you honestly won’t miss the stretch.

Temperature regulation and breathability 

What I want from a base layer is something that keeps me warm and dry. I thought all of that had gone out the window when I went out on a small skiff in high seas off the coast of Swansea last year on a Helly Hansen sailing trip and within seconds, a giant wave had dumped itself down the collar of my sailing jacket (I didn’t realize there was a hood). So, I was soaked from the inside out and, though it wasn’t freezing for November, it was cold enough. But I stayed out on the seas for a couple of hours and was really impressed by how warm (or not cold) I remained. It also served me well under other layers on a recent very cold ski trip, and I’ve worn it with my running jacket during a cold snap for trail running.

On the other end of the spectrum, I don’t overheat in it the way I sometimes have wearing merino wool base layers. It’s super breathable and I think I’d be comfortable wearing it in any mild to freezing adventures.

Weight and packability

This isn’t the lightest base layer I own, but it’s meant to be midweight and it's certainly not heavy or bulky. If you’re really worried about weight and pack size, one that is a single layer construction will definitely be a better choice, though it might also be itchy. For something that performs in harsh conditions, you'll want this base layer.

Odor control and durability

Merino wool is known for its great odor control, but the polypropylene lining of this means that it does get a little smellier. It’s nothing compared to an all-synthetic base layer, but expect to have to wash it after a couple of sweaty runs. That said, it’s a great quality garment with lots of staying power.

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Artilect W-Flatiron 185 Crew Td Tie Dye: first impressions

The Artilect W-Flatiron 185 Crew Td Tie Dye base layer may be marketed as a “warmer” base layer, but that’s underselling things slightly – it truly is a very hot winter base layer indeed. I made the mistake of wearing it out on the hills at the start of Fall and it was, frankly, too warm. You have been warned.

It’s maybe a little confusing because of the choice of materials. Designed with Nuyarn Australian Merino fabric, it exhibits all of Merino’s natural properties, but they are amplified, thanks to a twist-free fiber construction. That also means it’s really warm compared to other Merino ratings: what Artilect refer to as 185 would be a good 200+ in another brand.

You also get very full coverage. The cut is long in the arms and body, so lots of overlap with trousers to stop the back riding up under a ski backpack. It is high in the neck, which might not be to everyone’s taste, and has thumb loops to stop the top riding up beneath mid layers and to keep wrists extra cosy. Basically, your top half is thoroughly protected if you’re wearing this base layer in winter.

Artilect W-Flatiron 185 Crew Td Tie Dye: on the slopes

The Artilect W-Flatiron 185 Crew Td Tie Dye base layer has gusseted underarms with breathable panels that extend from waist to wrist. The fabric is very soft and I only got sticky when I was wearing it in way warmer weather than I should have been. 

Engineered seam and eyelet placements help increased both mobility and breathability. Despite the base layer being constructed from several connected panels, the seams are all flatlock stitched. This means there is no chafing or rubbing – and barely an awareness that the seam is there at all. 

The tie dye color scheme is very distinctly Artilect and it’s refreshing to see more brands step away from the standard black base layer. I’m not 100% sure the color is for me – honestly I keep yo-yoing between what color I think it is: more golden in some lights, more olive in other. But I imagine I’ll be wearing it most this winter, when it’ll be so far under jackets and fleeces, any misgivings about the color will be completely irrelevant.

• How Advnture tests products

As the foundation of your layering system, the best base layers provide comfort and warmth during harsh conditions and can also be worn solo when the weather heats up. A base layer is worn next to your skin, so it's important that your base layer feels comfortable, manages your temperature effectively, wicks moisture away and moves with you.

Many of the best base layers are made from natural materials, such as Merino wool or bamboo, or are created using synthetic materials, usually polyester. Hybrids are very common too, combining the insulation of something like Merino with the fast drying qualities of polyester and the stretchiness of elastane.

We've ventured into all kinds of conditions to bring you this definitive guide to the best base layers available in 2026. The Icebreaker 200 Oasis Long Sleeve Crewe Thermal Top is our highest rated base layer here. Its Merino wool content makes it super comfortable and the performance is second to none. We kick things off with this and other Merino tops, before moving on to blended options, synthetic tops and bamboo base layers.

The quick list

This is our quick list, a brief overview of the best base layers available. To delve deeper into the specifics of each garment, see our more detailed reviews further down the page in this guide.

The best base layers we recommend in 2026

The best base layer overall

The Oasis – weighing in at 200 grams square meter (gsm) – is an ideal thickness for a base layer, and unsurprisingly is one of the company’s best selling garments. Made from 100% Merino wool, we found this top to be supremely comfortable. On test, it wicked moisture away with aplomb and maintained most of its thermal properties when wet. It's also naturally antimicrobial, and therefore odor-resistant. 

It performed equally well for chilly trail running and trekking outings, and during a mid-winter sea paddle, though we would have appreciated thumb loops to keep the sleeves in lace.

As a natural material, Merino wool is biodegradable, and the dye used is plant-based and ethically sourced. Icebreaker has never been a bargain brand, and this isn’t a cheap top. The simple designs are cheaper, but for a little extra cash there are funkier prints available too.

Read our full Icebreaker 200 Oasis Long Sleeve Crewe Thermal Top review

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The most stylish Merino base layer

The Artilect W-Flatiron 185 Crew tie-dye base layer (the men's version is the M-Flatiron) may be sold as ‘warmer’, but it is actually a very hot winter base layer. Designed with Nuyarn merino fabric, it exhibits all of merino’s natural properties, but these are amplified thanks to a twist-free fibre construction. On test, we found the cut to be long in the arms and high in the neck, with thumbholes that prevented the top riding up beneath mid layers and kept our wrists extra cosy. 

The base layer top has gusseted underarms with breathable panels that extend from waist to wrist. Despite having several connected panels, the seams are all flatlock stitched, meaning there is no chafing and barely an awareness that the seam is there at all. It's definitely one of the most comfortable base layers we've tested.

The tie-dye color scheme is very distinctly Artilect and it’s refreshing to see more brands step away from the standard black base layer (even though that's something of a moot point when it's covered up under a fleece and jacket).

Read our full Artilect W-Flatiron 185 Crew Td Tie Dye base layer review

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The best lightweight Merino base layer

Named for Monte Zebrù in the Ortler Alps, this top is exceptionally light, but it punches well above its weight when it comes to performance. The majority-merino material offers everything that wool always brings to the party – breathable with excellent moisture-wicking capability, the ability to keep you warm when its cold and cool when it’s hot, natural odor resistance – but there is much more going on here.

The Zebru a figure-hugging bodymapped design, woven with ‘Responsive’ smart synthetic yarns including natural thermoreactive minerals that (according to Salewa) can absorb far-infrared radiation (FIR) from your body, and slowly release it back into muscle tissue, leading to better blood flow, improved oxygenation, longer-lasting warmth, enhanced performance and faster recovery. 

This all sounds very impressive, even if it is impossible to monitor, but having tested this top on the trails, we can attest to its excellent performance. It's a tight-fitting base layer, but the four-way stretch material means you can move easily while wearing it, and the next-to-skin comfort levels are good, with flat-lock seams causing no rubbing or annoyance. It is also styled long, so it doesn’t ride up your back, but disappointingly it lacks thumb hoops.

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The best hybrid base layer overall

With the Rho Hybrid, Arc’teryx have attempted to give you the best of both worlds offered by natural and synthetic fibres. The main fabric is their Phasic AR II, a midweight polyester that has been treated with silver ions to neutralise body odor, but there are also zoned panels under the arms made from a blend of natural merino wool and hard-wearing nylon. We discovered that the result is a hybrid design that does its job really well – a top that supplies great wicking performance, comfort and warmth, without any unpleasant odor.  

It also happens to have one of the best fits of any long-sleeved technical tee we’ve tested. It has plenty of length in the arms and torso, plus a stand-up collar that does a great job of preventing chills from creeping down your neck. The cut is trim enough to feel cosy without being skin-tight, unlike a lot of other compression-style winter layers out there. The deep neck zip is a great way to dump a little extra heat if you’re working hard uphill too. The fabric is soft and comfortable, with very thin, flatlock seams to avoid irritation.

It’s tempting to go cheap on your base layers – after all, they’re not generally the most exciting bits of kit. But we think a top-quality technical layer like this one is well worth it.

Read our full Arc’teryx Hybrid Half Zip base layer review

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The best hybrid base layer for warmth

Helly Hansen pretty much pioneered the concept of technical, high-performing base layers and they remain industry leaders when it comes to making good stuff that will keep you alive in challenging conditions, as the double-layer Lifa Merino Hoodie perfectly illustrates. ‘Lifa’ is the brand’s own high-performing polypropylene yarn, which is used in almost equal measure here with merino wool. On test, we found that both fabrics excel at doing all the things we'd want a base layer to do – they wick moisture away from the body and have excellent thermal qualities even when wet – but each also brings its own tricks to the party. 

The merino brings with it natural antibacterial and anti-odor properties, while the Lifa is more hard-wearing and helps keep the top in shape. A really comfortable top, with flat seams, this is the only base layer on test that had a hoodie, which people will either love or hate. If you’re out and about in seriously cold conditions, your ears are going to love it – it fits under climbing or bike helmet no problem, and really adds to the protection level of the top, making it suitable for high level epics on serious mountains. If you’re adventuring at a more modest level, this is still a lovely top, but you might find it a little too substantial to wear as a base layer.

Read our full Helly Hansen Lifa Merino Mid-weight Hoodie review

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The best hybrid base layer for breathability

Combining strict ethical production standards and technical functionality is a hard task, but the Smartwool Women’s Merino Sport Long Sleeve Top delivers on both fronts. Proudly boasting ZQ certification, not only does it feel good from a consumer perspective but the top also performance perfectly. 

The Merino Sport Long Sleeve top’s Tencel Lyocell fibres are comprised of composite recycled cellulose, making the garment, lightweight and super comfortable for a range of different active sports. Temperature regulation, odour resistance, and moisture management are all key features why many people opt for merino – but with this top users don’t suffer with the ‘damp  wool top feeling’ that you can sometimes experience with the material, thanks to this high-performing, recycled cellulose fibre. On test, we found it feels nice against the skin, helps minimise awkward sweat patches and makes the garment ideal for wear in-between temperature fluctuations. This is a product for all seasons. 

Our tester felt the sizing was somewhat generous, with extra room on the waist and arm length; she reports that a small felt more like a size 12 – so this is worth bearing in mind if you’re after a more fitted top.

Read our full Smartwool Women’s Merino Sport Long Sleeve top review

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The best value hybrid base layer

Made from a magical mix of merino and manmade polyester (32% of which is recycled), this simple-looking top is a lightweight, high-performing base layer that did everything we could have asked it for during the test period. The athletic-fit Forge kept us warm (even when wet), dried quickly, wicked moisture, refused to stink even after extended wear and kept its shape.

It will serve you well out on the trails all winter, worn as an active undergarment, but at this weight, it’s one of those pieces of kit that’s well worth stashing in a backpack (or even a hydration pack) all year round, in case a change of conditions catches you out and you find yourself in need of an extra layer. The only thing it is missing is thumb hoops, to stop the top riding up your arm when you pull on another layer.

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The best synthetic base layer overall

The polyester-based Parameta G material used to make this well-thought-through top features an ingenious raised-grid pattern that, when another layer is added on top, traps air between the squares. This air then becomes warmed by your body heat, providing a layer of thermal insulation. Clever. On test, if we ever got too hot, we could quickly release this air by taking off (or just unzipping) a mid layer or outer layer. Alternatively, in warmer conditions or during high intensity activity, the Grid Technic can be worn on its own, when it works as a standard poly top, providing decent levels of warmth (even when wet) and excellent moisture wicking properties. 

The Grid Technic has a high neck to keep your throat warm, which features a mid-length zip (with a good chin protector), so you can let cool air in when needed. It also has thumb hoops, so the base layer won’t ride up your arm when you pull another layer over the top, and your wrist won’t become exposed between the top and your glove. You shouldn’t suffer a chilly lower back, either, even when wearing a backpack, as the top is longer at the rear. The athletic cut means it fits closely (no annoying excess material flapping around) and the next-to-skin comfort is good, if not quite as luxurious as merino. As with the vast majority of Páramo garments, this top is made ethically in Colombia with the Miquelina Foundation, a member of the World Fair Trade Organization, and it is fully recyclable through Páramo.

Read our full Páramo Grid Technic base layer review

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The best recycled synthetic base layer

Produced by US brand Saxx, which specialises in making men’s underwear that provides comfort during active pursuits, the Roast Master long-sleeved top is a midweight base layer designed for cool weather use by hikers, bikers, runners, skiers, boarders, paddlers, climbers and campers. The material mix is predominantly recycled synthetics, combined with Tencel lyocell, an eco-friendly fabric where the fibre content is derived from sustainable wood, and elastane is also used to provide some stretch, so the top won’t inhibit your movements on the hillside, mountain top, water or crag. 

Our tester reported that: "While I never felt my movement was impacted or restricted by the top, the degree of stretch is not as pronounced as in some base layers I’ve tested… [and] despite Saxx saying it’s a slimfit garment, I found the Roast Master to be slightly over-generously sized." So, if you prefer a body clinging base layer, choose a size smaller than usual. The material is breathable, wicks moisture away from your skin, will continue to work and provide thermal protection even when damp, and it dries extremely quickly. Saxx says this garment has been treated with an anti-stink product, but only time will tell if this works. The flat seams and soft-finish inner make it exceptionally comfortable to wear, and it should last for many seasons. Our main criticism of this top, beside the sizing issue, is the lack of thumb loops. 

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The best synthetic base layer for dynamic movement

Although it has a pretty pedestrian appearance when being worn, if you turn this top inside out, it looks almost metallic, and resembles something you might see worn on the bridge of the starship Enterprise. As with everything they make these days, Columbia have employed their trademark Omni-Heat technology in this base layer, in a bid to keep the wearer warmer than any other brand. The Omni-Heat concept involves the use of loads of soft fiber pods, which create a little gap between the garment being worn, and your skin – your body heat then warms the air trapped inside this space, and the silver lining of the top reflects this heated air back at you. Genius.

In addition, because there’s a space between your body and the base layer, less moisture builds up, and the poly fabric of the top wicks sweat away too. This all sounds impressive, but it does actually work too – in fact, it worked so well on test that we could often feel pretty hot in this top, although shedding an outer layer generally sorts that out. If you’re heading somewhere seriously cold – like a mountain top, or a ski resort – this is a great option.

Read our full Columbia Omni-Heat 3D Knit Crew II base layer shirt review

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The best sustainably-made synthetic base layer

At first glance, this thermal top looks fairly basic – it’s here to do a job for a fair price with no bells and whistles, true enough – but there’s more of a backstory to these base layers, because they are made from recycled plastic. Around 10 to 12 discarded bottles go into each garment, and while we know microfibres still get released every time synthetic tops are washed, it’s certainly better to buy something recycled. Craghoppers’ sustainability policies are solid, and the brand also guarantee their garments for life (as in, the clothes expected lifespan), and will take used garments back to recycle them once they’ve been worn out.

A relatively thick top, we found its performance levels were excellent: in our tests it kept us warm, wicked moisture away, and absorbed very little water, letting it keep its warmth-giving capabilities even when wet. On the down side, it lacks thumb hoops, but it is available in a short-sleeve iteration, for year-round use.

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Best base layers comparison table

How we test base layers

Our reviewers test base layers in a range of environments and conditions, from wintry hills and peaks to warm hikes along the coast, mixing day hikes and longer expeditions. Features (including breathability, odor-resistance, ventilation, materials, style, weight and overall comfort) are tested against claims made by the brand, and we assess factors such as value for money, durability, functionality and environmental impact.

Meet the testers

How to choose the best base layer

While there are myriad styles to choose from, the best base layers are there to do one job well: keep the wearer warm and safe. Additional features will add comfort and functionality, but the thermal properties are the most important factor. The following are some things to consider.

Thermal insulation

The best base layers work by trapping air, which is then warmed up by your body heat to provide a thermal layer. For this to work well, the garment must be made from a material that holds on to air well, but gets rid of water quickly.

Materials

Natural fabrics – especially merino wool, but also bamboo – work very well in the best base layers, but you’ll often see manmade materials like polyester and Lycra employed in the mix, and these can help make the garment closefitting (as a base layer should be), maintain its shape, add to its durability and improve the all-important thermal performance, especially if it gets wet. 

Merino wool is a magic material that keeps you warm when you need it to, but can also cool you down when outside conditions are hot. It also wicks moisture away from your body, feels comfortable and boasts antibacterial properties, which stop tops from getting too smelly. Garments with a high percentage of cotton should be avoided, as cotton holds onto water and performs terribly when wet, losing all its thermal properties and keeping you cold.

Comfort

Next-to-skin comfort is very important in a base layer, for obvious reasons. Most people find merino wool extremely comfy, but others prefer bamboo, or synthetics such as brushed fleece. This is subjective, but worth getting right, otherwise you’ll spend all your time itching. Tops with flat-lock seams will be more comfortable to wear.

Fit

Ideally, the best base layers need to hug you tight. You don’t want the back of the sleeves riding up to expose bare skin to the cold, and a top that wrinkles under another layer won’t be comfortable.

Features

Lightweight base layers are less likely to have them, but in a more substantial base layer, a partial-length zips is an excellent feature, allowing you to dump excess heat during activities. We like thumb loops too, which stop sleeves from riding up when you put on another layer, and prevent gaps appearing between your top and your gloves.

Moisture management

While outer layers have to cope with mist, rain and snow, base layers must deal with sweat, so they need to be breathable and have the ability to wick moisture away from your body.

Weight

Base layers are often ascribed a weight (for example, ‘midweight’), which relates to the thickness of the piece of clothing in question. Obviously, the higher the weighting, the warmer the garment will be. It’s definitely possible to have a base layer that’s too hot, so go with an option that best suits the type of outdoor activity you do most often, in the kind of conditions you’re most likely to be out doing it in.

Durability

While merino wool is one of the best base layer materials, it does only last so long and it can lose its shape, which is why many brands use a mix of wool and hardier synthetic fabrics.

Environmental concerns

As always, the most sustainable clothes are the ones you’ve already got, but if you do need to invest in a new base layer, look for garments woven from natural, biodegradable materials (wool, bamboo) or recycled synthetics, made with natural dyes by brands with good environmental principles and robust manufacturing ethics.

Our guide to the most eco-friendly outdoor brands will point you in the right direction.

Thermals, long johns… whatever you want to call the best thermal underwear for women, there’s nothing like a warm layer worn next to the skin to help keep the chill of winter at bay. Whether you’re off skiing, hiking or cold-weather camping, layering up is the best way to trap in heat and keep cosy in the great outdoors – and a good layering system starts next to the skin, with the best women’s thermals – both tops and leggings.

You can choose thermal garments constructed from various comfortable and cosy materials. You’ll find our full buyer’s guide below for help on how to find your perfect thermal set, but among our top picks are BAM’s soft bamboo cold bashers, Icebreaker’s moisture-wicking Merino wool options and Odlo’s eco-friendly recycled polyester thermals, which all really stood out on test. 

If you don’t find what you’re after here, check out our guide to technical base layers and/or running underwear. 

The best thermal tops for women

Merino really is a bit of a wonder material for thermals and base layers – it’s naturally warm but breathable and it wicks away sweat, so it’s perfect if you’re getting active. 

It also naturally resists odors – ideal if you’re camping or skiing in the backcountry for several days at a time, without the luxury of changing your base layers – and it is soft and comfy against the skin, unlike other wool base layers, which can be scratchy. 

Merino can be expensive, but we reckon Keela’s simple, crew neck, long-sleeved base layer is well worth its sensible price tag – it’s smart, easy to wear with everything, great quality and should last you for years of outdoor adventures.

Ultra-comfy, organic and highly breathable, bamboo is a fantastic material for sportswear. And BAM’s sport-friendly base layers aren’t just comfortable – they’re smart enough to wear as regular tops and leggings when you aren’t out on the trail. 

The stretchy Perform top is supremely comfortable and moves when you do whether you’re walking, climbing, skiing or cycling. We also love the thumb holes, handy for trapping warmth in and keeping sleeves in place if you’re wearing gloves on top. 

Effective antibacterial properties make bamboo a clever choice for camping or backcountry expeditions: you can hike for days in this anti-odor base layer jersey without offending the noses of your hiking companions.

A firm favorite with gym fans and sporty types, Under Armour’s Cold Gear range is designed for use in the winter months, and can be relied on when temperatures drop. 

A simple design and a flattering fit make this mock neck top a pleasure to wear, and we found the great stretch was ideal for more vigorous activities, where you don’t want to notice you’re even wearing a base layer as you move. 

What’s more, although polyester is not a very eco-friendly material, of all the base layers we’ve tested, the Cold Gear top proved the fastest to dry, and the best at wicking away sweat. Perfect for anyone who likes to get really active in the great outdoors in milder winter weather. 

Cornish brand Finisterre make great quality outdoor kit in nature-inspired colors, and their bamboo range of thermals and base layers are stand-out pieces for winter layering. 

We like these soft neutral tops (they also do matching bottoms) because they work so well as casual day-to-day clothing as well as for active adventures, unlike sportier-looking base layers. The bamboo wicks away sweat brilliantly and is a vegan option, unlike Merino wool. 

This bamboo layer has some stretch but is quite tight-fitting, so you may want to pick a size up if you like a boxier fit. Wear this breathable top in the shoulder seasons; if you need an alternative for colder winter weather, Merino has sets designed for that too.

The best thermal bottoms for women

Keep the bottom half of your body super snug in these woolly tights. We love wearing these Alpspitze leggings as a base layer for walking and skiing – they’re delightfully warm, they stay put all day, they’re highly breathable and they sport a great wide waistband so comfortable that you’ll barely notice you’re wearing them. 

Unlike synthetic bottoms, these wool leggings have a soft, natural feel against the skin. They’re also treated with an anti-bacterial treatment that keeps them feeling – and smelling – fresh even if you do get sweaty. 

These are firmly in the “underwear” rather than the “leggings” camp – it’s a pity they’re too thin and see-through to work alone as workout bottoms, but as breathable long johns they’re a great quality choice. 

The best thermal top-and-bottom combos

We’ve put the Blackcomb thermals through many months of outdoor adventures, and they’ve never let us down. These soft synthetic garments are comfortable and form-fitting (yet still flattering), with a ribbed shape that stays put all day – and they’re so light it barely feels like you’re wearing anything at all. 

They’ll keep you snug in snow, but are breathable and comfortable enough to wear alone, and they’re durable too: we’ve washed them multiple times and they always come out looking and performing like new. Tops are available with and without high necks, and with an optional face mask built in for the coldest climates. 

The new Eco versions of the Blackcomb collection are crafted with recycled materials.

Buy the Odlo Women's Blackcomb Eco Long Sleeve With Facemask

Buy the Odlo Women's Blackcomb Eco Bottoms

On bitter winter days when you’re skiing up a storm or trekking to windy mountain tops you’re going to need base layers that go the distance. Enter Icebreaker’s 250 range. 

These thicker, heavier and very warm base layers are less breathable than lighter thermals but they offer instant welcome warmth and can really make a difference when temperatures drop. We also like sleeping in them on winter camping trips. 

Merino wool once again offers a comfortable, moisture-wicking and antibacterial triple whammy. Last but not least, the Vertex top and bottoms look rather fetching, in bold geometric designs that Icebreaker call “Fractured Landscape”.

Buy the Icebreaker Women's Merino 250 Vertex Long Sleeve Crewe Thermal Top Fractured Landscapes

Buy the Icebreaker Women's Merino 250 Vertex Thermal Leggings Fractured Landscapes

A cult favorite among fitness bloggers, Sweaty Betty’s retro-looking thermals bases aren’t just good-looking, they’re also wonderfully comfortable and warm to wear. 

These synthetic knitted layers are primarily aimed at skiers, but the seamless design means they won’t dig in anywhere, so they’re ideal for sports and fitness, as well as providing warmth when you’re out and about. 

We particularly like the high waist and wide waistband on the leggings and the zip neck of the top. Our only criticism is that the insides of these thermals are quite delicate – they need gentle washing, and threads can come loose or snarl up if you catch them on jewellery.

Buy the Sweaty Betty Ski Jacquard Base Layer Leggings

The best thermal onesies

Okay, so it’s cute, but before you write off Mons Royale’s Monsie as a style-focused option, take a closer look. 

The New Zealand brand call their one-piece “the ultimate base layer”, and it’s actually a pretty clever choice – it’s made of 100% Merino wool, for great softness, moisture wicking and breathability, and on test we found that wearing an all-in-one did trap in more warmth than two separate pieces. 

A front and rear zipper make it easy to ventilate the suit (and to stop for loo breaks), the hood protects your head and at just 190g this suit won’t weigh you down. Plus, the Monsie looks enough like casual clothing that you can lounge around it in at après ski. 

Coolest base layer for warmer weather

Most base layer tops we recommend have long sleeves, but when you’re hiking in changeable conditions in spring and fall they can be overkill. 

Montane’s Dart T-shirt is a great versatile base layer that can be worn alone to keep your core warm in warmer weather, under a light mid layer in the shoulder seasons or just down the pub with jeans when you’re back from the hills. 

Round neck or zip neck versions are both available. At a smidge under £30 each it’s definitely worth adding one to your base layer collection for chilly but sunny days.

How we test women’s thermal underwear

Our testers have used the best thermal tops and thermal leggings for women on cold-weather hikes and ski trips, and compared them for warmth, breathability, comfort, cost and durability. 

How to choose women's thermal underwear

What constitutes the “best women’s thermal underwear” largely comes down to personal preferences, but comfort and functionality should really take precedence over fashion, since they’re not usually going to be a garment that you’re seen in out in public. We recommend that you take the following factors into consideration when looking for the best women’s thermals for you.

Fit

It’s definitely worth trying thermal base layers on in person, especially if you’re on the tall or short side – they should hug your body without feeling too restrictive around the waistband, ankles, neck or sleeves. Some base layers are stretchier than others – we reckoned thermals with some stretch offered more warmth on test, as there’s no empty space between the fabric and your skin for the cold to creep in. When you try on leggings and tops, check that you can move your arms and legs freely, with no baggy space. In particular, look for snug cuffs on arms and ankles; we always look for a wide, comfortable waistband on leggings too. 

Style and length

Thermal tops usually have a round crew neck or a high, zipped neck – the latter can double up as a neck warmer, and some tops also sport hoodies for extra warmth around your neck and face. Base layer tops are available with long sleeves or in T-shirt cuts; we usually pick long-sleeved options as they feel comfier worn under mid layers or a waterproof shell. We also look for base layers that use flatlock seams – this avoids any rubbing against your skin.

Materials

Base layers are usually made from either synthetic materials, such as polyester or a polyester blend, or natural materials such as wool and Merino wool. The advantages of polyester are that it’s very light and quick to dry, and that it’s often more affordable. Merino wool (either 100% Merino or a stretchier blend) tends to be pricier, but it’s very soft, long-lasting, naturally antibacterial and can be better at wicking away sweat, so it typically doesn’t need washing so often – perfect if you’re planning an extended camping trip that will take you away from showers and washing machines for a few days.

Wool base layers can be slightly itchy, so they’re definitely worth trying on in person to check before you buy. You may also find that a Merino blend will have more stretch than pure wool. A third, relatively new option, is bamboo clothing – this vegan material is also antibacterial, often wonderfully soft to wear and more eco-friendly to produce than synthetic materials. 

Thermals and base layers by numbers

You may see base layers listed with a number, such as 140 or 220. This refers to their weight in grams, and the higher the number, the warmer, but heavier, the base layer will be. For example, a 140g base layer is ideal for spring and fall, while a 220g will do a good job of keeping you warm in winter. If you can afford to, invest in two sets – one lightweight and one heavyweight – and you’ll be sorted year-round. 

What to do with your old thermal underwear

Naturally there isn't much demand for second-hand thermal underwear, but you can make yours last longer by doing a few DIY repairs. Don't worry if your work isn't the neatest, nobody will see it.

Once your thermals are well and truly worn out, you still have some options to keep them out of landfill. If you're in the UK, the Waste and Resources Action Program (WRAP) has a postcode search tool that will help you find your nearest textile recycling drop-off point. If you live in the US, Subset  (formerly known as Knickey) specializes in taking underwear and socks, which are then turned into things like insulation, carpet padding, and furniture batting. You'll also get a voucher for up to $20 off your next purchase.

Highlander Bamboo Base Layer Long Sleeve Top: first impressions

Scottish outdoor company Highlander has been making affordable outdoor gear since the mid 1980s to help more folks weather the elements without breaking the bank. In this base layer, they’ve combined flat lock seams with the soft, breathable properties of bamboo for next-level comfort and created a first layer that will help keep you cool in mild to warm conditions. 

The body-hugging fit of this base layer looks great and makes it really easy to layer a fleece jacket on top. Though like most bamboo products, it’s slow to dry once it gets soaked, the antibacterial properties of bamboo mean it doesn’t get too stinky and doesn’t need to be washed after every use. It doesn't feature thumb holes, but since the thin construction slow-dry properties make it better suited for warmer weather, that really doesn’t matter, and the sleeves are nice and long. At such a low price, it’s worth picking up one or two of these for milder adventures, especially if you have sensitive skin.

Highlander Bamboo Base Layer Long Sleeve Top: in the field

My first impression upon pulling this base layer out of the packaging was how velvety soft it is. Like, even for bamboo it’s crazy soft! But, sure, it feels amazing against my skin, but is it really up to the challenge of sweaty adventures where I need to regulate my temperature?

Here’s how it performed:

Comfort and fit 

I’m typically slightly larger than an XS and smaller than a S in most brands, and for this one I decided to size down. I think it fits perfectly, it is really snug, but that makes it easy to layer on top, and it’s so stretchy that the snug fit doesn't hold me back. Either order your normal size, or size down if you like your base layers to be body hugging.

As for comfort, well, wearing this thing is like wearing butter. It feels incredible on my skin. All bamboo clothing is soft, but this one really takes the cake. Flat lock seams add to the comfort level, which means no chafing or rubbing anywhere.

Temperature regulation and breathability 

Here’s where I get a bit stuck with bamboo. Everyone who makes clothing out of bamboo rayon or viscose says it’s quick drying, but I don’t find that to be true, at all. In fact, I find that this top, like other bamboo clothing I’ve worn, gets quite damp when I work up a sweat in it, and it stays wet. In fact, I’ve been caught out when I’ve tossed it in the laundry basket, then decided I want to wear it again the next day only to discover that it’s still wet. So, it’s definitely not quick drying, unless you’re comparing it to a rubbish bag, but it is breathable, which means that sweat is able to passively leave my skin while I’m on the go, so I don’t feel like I’m running in a rubbish bag.

All this means that it does help keep me cool when it’s mild or warm, but, combined with fairly thin fabric, I wouldn’t say it’s the best for keeping warm. However, if you’re not working up a sweat, it will provide some warmth as a first layer.

Weight and packability 

This base layer is thin and lightweight, ideal for fast adventures, and it folds up nice and small. It also doesn’t get crumpled easily (unless it’s wet) so it’s great for travel.

Odor control and durability

Bamboo might not be as quick drying as people make out, but one thing I do like is its odor control. Due to natural antibacterial properties, I’ve left this base layer sweaty and scrunched up in my backpack, then hung it up to dry and found it easily passes the whiff test. It might not have quite the odor-control of merino wool, but it’s miles better than synthetic. I haven’t had this long enough to see how it stands up to multiple uses and washes, but I will say that my experience with bamboo is that it’s not as durable as other fabrics. Time will tell.

• How Advnture tests products

EDZ Merino Base-Layer Long Sleeve 200g: first impressions 

EDZ is based in Cumbria so they know a thing or two about cold, wet weather, and they’ve come up with just the solution in this base layer. They’ve gone all in on performance and sacrificed flashy patterns, zips and thumb holes to deliver serious warmth in a classic cut base layer that looks as good around town as it does under your best fleece jacket or waterproof jacket when you’re out in the hills.

The 100% merino wool composition means this is a winner for wicking away sweat and staying dry when you’re pushing boundaries, and it remains odor-free for quite a few wears without getting wrinkly, making it great for travel, too. Though merino wool is also known for helping you stay cool in hot weather, this base layer is definitely better suited for cold weather expeditions since it traps some serious heat, and for the price it can’t really be beat. 

EDZ Merino Base-Layer Long Sleeve 200g: in the field 

I love a good merino wool base layer for the majority of my outdoor adventures in most seasons, so I’ve been enjoying testing out a few new ones for Advnture this year and I have to say, this is easily the toastiest one I’ve worn. Made with 100% merino wool, it’s a high performer and I still can’t believe the price.

Here’s how it performed:

Comfort and fit 

This base layer fits true to size and wears close to my skin with a classic cut. Though it doesn’t have any added stretchy fabric, it’s woven to provide ample mobility (I’ve even worn it during yoga) and it doesn’t rub or catch anywhere.

I don’t want to go so far as to say it’s scratchy, because it isn’t, but I have worn merino wool base layers that are softer (because they were blends). My boyfriend is particularly sensitive to wool and, having felt this, he doesn’t think he could comfortably wear it, so I think if you’re sensitive to wool, you may not be able to wear it, but for me it’s no problem.

Temperature regulation and breathability 

Because the wool isn’t blended with anything else and it’s their heaviest duty base layer at 200gsm, this base layer is seriously toasty. I’ve taken to wearing it around the house and a couple of times I’ve gone out wearing it with a winter coat on top, hopped on the bus and almost melted. It is fantastic for cold weather adventuring, but I think it would be too hot for summer, even if it does wick sweat.

It’s merino wool so I probably don’t have to tell you it’s really breathable and doesn’t get soggy, even when I’ve worn it out on a wet, cold trail run.

Weight and packability 

I tested a women’s small which tips the scales at just five ounces, so there’s never going to be an instance where I would question throwing this in my backpack, and without extras like zips it folds up nice and small.

Odor control and durability

I’ve been able to wear this for multiple hikes in a row without washing it, which is ideal, and I’m pleased to say that it is machine washable when it does get stinky. Merino wool isn’t typically as durable as synthetic fabric, but with a couple of months of use it’s still looking great. 

• How Advnture tests products

Gearing up for a winter outdoors requires a whole slew of insulated clothing that you might never have needed before, all the way down to your skin where you’ll want to wear thermal underwear beneath those thick, outer layers. But wait, does that just mean a fleecy pair of boxers or a G-string made using goose down? 

What is thermal underwear and do your nether regions really need that much protection from the cold? In this article, we answer all your common questions about thermal underwear, including what to look for and how to wear it to stay warm and dry all winter long.

What is thermal underwear?

Thermal underwear are thin, stretchy pants that are usually worn underneath clothing, such as your hiking pants or ski pants, to provide an additional layer of insulation during outdoor activities. They look a lot like a pair of leggings and are also known as long underwear or long johns.

In the hiking layer system, thermal underwear forms part of your base layer, along with a long sleeved top made of the same material, and the two terms are often used interchangeably to describe both the top and bottoms, a bit confusingly. For this article, however, when we say thermal underwear we’re speaking about the bottoms.

We also find that thermal underwear can also make good pajamas to wear inside your sleeping bag when you’re camping in cold weather.

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What makes thermal underwear thermal?

• Thermal underwear is usually made from either Merino wool or polyester
• Merino wool traps air, providing excellent insulation  
• Both wick moisture brilliantly, making them very quick drying
• Polyester is more affordable than Merino

If thermal underwear looks and acts a lot like a pair of leggings, can you just wear an old pair of cotton leggings under your hiking trousers to stay warm on a winter hike? Assuming you’re not going to sweat or otherwise get wet, this would certainly provide some more warmth, but what makes true thermal underwear thermal is typically the fabric that it’s made from, and sometimes the construction. 

When we’re talking about thermal underwear for active pursuits like hiking and skiing, then good thermal underwear is usually made using Merino wool, such as the Icebreaker Merino 250 Vertex Thermal Leggings. The benefit of Merino wool is that it traps air to provide insulation, and wicks away moisture to keep you dry if you get sweaty, and dries quickly.

The main downside of merino wool, however, is that it’s expensive, so lots of great and more affordable thermal underwear is being made using synthetic fibers, such as polyester, which shares similar moisture-wicking properties to keep you warm and dry.  Some, such as the Smartwool Intraknit Merino 200 bottoms, are made using a merino wool/synthetic blend. If you’re very sensitive to wool, you’ll appreciate the non-itchiness of synthetic alternatives, too. You might also see some thermal underwear made using bamboo rayon, which will trap air and wick sweat, but most bamboo clothing is slow to dry, so for high-energy frigid adventures, it may not be your best choice.

Active thermal underwear may also be constructed using two thin layers of fabric, to better help trap heat. The most important thing to know is that if you’re shopping for thermal underwear for outdoor adventures, you’ll want to avoid cotton since that won’t dry quickly or keep you warm if it gets damp – save these for days when you’re working from home and want to keep your central heating bill down.

Do you really need thermal underwear?

• Thermal underwear is for cold winter adventures
• They're great for downhill skiing, winter mountaineering and wild camping
• Wear your usual underwear underneath them and your hiking pants over the top

If you’re adventuring in cold weather, it’s a good idea to own thermal underwear though you won’t always wear it. It all depends on how cold the weather is, and what you’re going to be doing. Assuming we’re only talking about the bottoms, your legs probably don’t feel as cold as the rest of you in winter, so if you’re really exerting yourself on a hike or uphill skiing, you won’t need long johns unless it’s well below freezing, especially if you’re wearing insulated pants. 

However, for very cold temperatures, downhill skiing, winter mountaineering and winter camping, they can be life-saving. Wear them with your regular underwear underneath, and warm layers like a down jacket and windproof hiking trousers over the top and you’ll stay toasty all day.

Should thermals fit tight or loose?

• Thermals should have a body-hugging fit
• This is because their insulating properties work best when tight against the skin

Any base layer should be snug-fitting, and that’s not simply so you can get your clothes on over the top. The air-trapping insulating properties of your thermals work best if the material is held close to your skin. If slim-fitting clothes annoy you, look for thermal underwear with more than 10% stretchy fabric to make it easier to move.

How long can you wear thermal underwear?

• You don't have to wash thermal underwear as often as regular underwear
• Merino wool has antimicrobial properties, which means it's resistant to odors
• Even polyester thermals are often treated with an antimicrobial treatment
• General guidance is that you can wear the same pair for 3-5 days

Hopefully you wash your regular underwear and each use, but the good news is that you won’t have to wash your thermals quite so frequently. If your thermal underwear is made using Merino wool, it will have some naturally antibacterial properties while synthetic garments meant for active use are often treated to be antimicrobial. All this means is that they inhibit the growth of microorganisms and don’t get as smelly, especially if you go for Merino wool – for hopefully obvious reasons, you can enhance this by wearing regular underwear underneath your thermals.

So to get back to your question, how long can you wear thermal underwear? Lots of outlets say you can wear them for 3 - 5 days, based on manufacturer recommendations, but obviously it all depends on what you’re doing in them, how much you sweat and whether or not you air them out when you get home or leave them scrunched up at the bottom of your backpack to fester. Basically, hang them up to air them out after a hike and use the good old fashioned sniff test and know that you’ll be able to wear them for at least a handful of adventures without washing them.

Can thermals be worn alone?

• Thermals work brilliantly on their own for dynamic winter activities
• However, they don't provide much of protection against wind and precipitation

If thermals are body-hugging, sweat-wicking and insulating, you might well be wondering if you can wear them without clothes on top, and the answer is yes. Particularly for sweaty adventures like winter running and cross country skiing, they can provide better protection against the cold than a simple pair of leggings without making you overheat. 

They won’t offer a ton of protection from the wind or any shield against wet weather, but in dry climates like Utah and Colorado, you could wear them for a winter hike without outer layers if you see fit, and then there’s no annoying swishing of weatherproof membranes like Gore-Tex while you walk. Some look a lot like underwear, but lots of them are fairly stylish nowadays, so you can wear them around town too if you want.

So you’ve been reading articles about what to wear hiking or perhaps shopping for a new hiking shirt and you’ve seen enough to know that you absolutely need a base layer any time you’re going out into the hills. But what is a base layer anyway, and why does it matter when you’re active? It turns out that a lot of you have a lot of reasonable questions on this topic, so we set out to answer them here to help you set off on your next adventure fully prepared and comfortable. 

What is a base layer? 

As you may have heard, there’s no such thing as bad weather, only the wrong clothing. In hiking, as well as winter sports and trail running, we dress for all conditions using the hiking layer system and a base layer is the layer of clothing that you wear next to your skin, over which you layer warmer and waterproof clothing. The term is usually used to describe your top, however it can also include bottoms, such as long johns that you might wear under your hiking pants. Beyond that, a base layer can come in a variety of different fabrics and styles, from tank to tee to long sleeved.

What is the point of a base layer?

OK, so if a base layer is just the piece of clothing you wear next to your skin, can’t you just call it your T-shirt and be done with it? Well, sure, but there’s another element to base layers that we haven’t discussed yet. A base layer needs to provide some thermal properties, and also, importantly, it should help to transfer sweat away from your skin to keep you dry while you’re active. In order to form part of your layering system, your base layer needs to be breathable and moisture wicking. This allows you to stay cool once you start to break a sweat in warmer weather, and keeps you from becoming chilled in cooler weather since it won’t simply absorb liquid and leave you hiking in a clammy shirt.

For this reason, a good base layer will be made with fabrics such as merino wool, like the Icebreaker 200 Oasis, or synthetic materials like the Montane Dart which is made from polyester.

Is a base layer the same as thermals?

Yes, while base layer is the more common North American term, in the UK the term “thermals” is more common to describe the layer closest to your skin that helps you manage your temperature.

Do you wear anything under a base layer?

Great question! On a chilly day, you might be used to wearing a cotton tank (or vest in the UK) under your shirt, but this will actually impede the effectiveness of your base layer as once you get going you’ll just be wearing a damp, cotton undershirt against your skin. Base layers are meant to be worn on their own, however if you hike wearing a bra, it’s a good idea to use a sports bra that is also sweat wicking so that it forms part of your layering system. Similarly, if you’re wearing long underwear, it’s a good idea to wear regular underwear for hygiene purposes, and if that means something with a lot of coverage like boxers, look for something sweat wicking such as running underwear.

Can you wear a base layer on its own?

Yes, definitely. Even though your base layer might essentially take the place of an undershirt, in many instances it will actually be the only layer that you’re wearing. In warm weather, you might set off wearing only your base layer and carrying a fleece and waterproof jacket in your backpack. However, even in cold weather, when you start climbing you can get warm and start sweating quite quickly, so there’s a good chance you’ll be stripping away those outer layers until you stop for lunch.

How tight should a base layer be?

In order for a base layer to work properly and wick away sweat, it does need to be fairly form-fitting and actually touch your skin. For that reason, it’s good to look for one that has a decent amount of stretch such as the Megmeister Drynamo Winter High Neck to allow for good freedom of movement. That said, perhaps a better technique is to simply try it on and make sure you can move your arms comfortably in it.

The only exception to this is a base layer that you plan to wear on its own during warmer weather – since it’s not part of your layering system, it can fit a little looser.

At what temperature should I wear a base layer?

There are differing opinions on this, with some people saying that you need a base layer for any adventure taking place in below 60°F (15°C) weather. In all but hot temperatures, where you can probably hike in your favorite tank top, we think it’s a good idea to wear a base layer, especially since they can be worn on their own. The key is to own several different base layers, including a very thin and light one such as the Rab Forge for milder conditions, and a thicker shield against frigid temperatures, like Helly Hansen’s Lifa Merino. 

Can I use leggings as a base layer?

If you’re thinking about your bottom half, you can definitely wear leggings as a base layer since they are snug, but remember, they have to also be sweat-wicking to work. That means no cotton leggings, but any of the best running leggings will be ideal and of course can double as outerwear too.

• Why is cotton bad for hiking?

If you leaf through an outdoorsy magazine, you could easily come away from it thinking that flannel shirts are synonymous with hiking, filled as they are with shots of broody-looking men wielding camping axes and gazing wistfully into the woods. The lumberjack look of a cozy flannel might scream rugged and capable in the outdoors, but a flannel shirt is a far cry from the synthetic hiking shirts and merino wool base layers that tend to dominate the hiking market and trails today. So is flannel really good for hiking? Or is it a product of cultural nostalgia that belongs with jeans and Doc Martens – in your closet but not actually on the trail? Let’s take a look at this outdoor staple to see if it’s really just for hipsters, or if you should wear it on your next hike.

What is flannel?

First off, it’s helpful to understand what flannel is, and isn’t. Rather than being a distinct material, like nylon or silk, flannel is a woven fabric that was originally made from yarn or wool, and today is usually made from cotton or a synthetic fiber like polyester. Flannel is brushed on both sides after it is woven, which gives it its distinctive soft feel against your skin, and is commonly used to make shirts and bed sheets for winter.

Is flannel good for hiking?

First off, what clothing is good for hiking does depend in large part on where you’re hiking. Colorado’s arid climate and perpetual sunshine differ in almost every way from the rainy UK, for example, with the latter requiring serious wet weather gear like a waterproof jacket and pants, while in the former, rain coats usually stay squashed in the bottom of your backpack and quick drying fabrics will suffice.

Generally speaking, flannel is soft and warm, breathable and durable, so on the surface of things, it sounds great for working up a sweat somewhere chilly. It feels good against your skin, keeps you cozy when there’s a cool breeze, has a loose enough weave to let perspiration evaporate and will hold up against backpack rub and sharp branches overhanging the trail. But as we’ve already mentioned, flannel can be made from different materials, so it’s important to seek out the right flannel if you’re planning on hiking in it.

Flannel made from cotton will have similar properties to other cotton clothing, and if you’ve read our article on why cotton is bad for hiking you’ll realize it usually isn’t ideal for a day in the hills. Cotton is a very absorbent material, meaning that it holds water, so if you get rain or sweat-soaked, you’re going to stay soaked. In hot weather, this may just mean that your natural cooling system (sweating) doesn’t work as well because your sweat isn’t able to evaporate off your skin (and who wants to wear a flannel shirt on a hot hike, anyway?) while in colder weather it can be positively dangerous, because you’ll get cold and stay cold. In arid, mild conditions, a flannel shirt made from cotton is probably alright for hiking, but generally speaking, it’s a good idea to save these shirts for hanging out in Brooklyn.

Now, true flannel made from wool will have similar properties to regular wool, which you may know is a great fabric for hiking. Wool keeps you warm when it’s cold out, but is breathable and moisture-wicking, meaning it helps to cool you off when it’s warm out and you start to sweat. It’s also somewhat hydrophobic, meaning it’s even functional in a rainy climate, and it doesn’t get stinky easily even when you sweat in it a lot. So a flannel shirt that is made from wool could actually be a great choice for hiking in lots of places in all but very hot conditions, and when it’s very hot of course you can just tie it around your waist.

Then there’s a third option, and that’s flannel made from synthetic material, such as the Alpkit Woodsmoke or the Marmot Ridgefield Sherpa-Lined Flannel which are both made using polyester. This means they are breathable, moisture wicking, quick drying and also combat odor effectively. Again, these will likely be too warm for summer adventures, but that’s just the nature of flannel shirts, no matter what they’re made from.

So, as long as you get one that isn’t cotton, you could actually do a lot worse than a flannel shirt for hiking in mild or cold temperatures, however, there are a couple of stipulations to that. 

First, to be effective, your flannel shirt should really be part of your hiking layering system and should be considered a mid layer. Since you may get too warm in it once you start climbing, it’s a good idea to wear it over another thinner layer, and that also has to be moisture wicking in order for the whole system to work. Layer yours over a white cotton tee like you do in Hipsterville and you’re back to square one, but wear it over a tank top or thin tee made from merino wool or another moisture-wicking material such as Icebreaker’s Cool-Lite Amplify Short Sleeve or the Montane Dart. Then, make sure you layer something breathable over it as well, such as a fleece jacket. With this system, you should be able to find comfort in many different temperatures even while moving vigorously.

The other thing to pay attention to is the presence of stretch. Traditional flannel shirts didn’t have any stretch at all, which doesn’t make them ideal for hiking or anything else where you’re moving fairly dynamically, reaching up to tighten your hood or taking your backpack on and off. Nowadays, however, you can find flannel shirts that are intended to be activewear and therefore have some stretch – particularly if you like your flannel shirt to be form-fitting, look for at least 5% spandex, lycra or elastane so you can move comfortably.

So there you have it. If you just love the look and feel of a flannel shirt, now you know how to make the most out of yours on cool hikes.

• The advantages and disadvantages of bamboo clothing

The North Face Mountain Athletics Bra: first impressions 

The North Face Mountain Athletics Bra is designed to create support during high intensity activities as well as long-lasting comfort when you’re hitting the trail for hours on end. Made using The North Face’s FlashDry fabric, this good-looking sports bra wicks away sweat and dries quickly to keep you cool and comfortable.

The square-shaped collar, thick straps, and broad elasticated band around your ribcage provide good coverage and give maximum support when you’re running, while soft jersey fabric and flat-locked seams mean no chafing, even on long days. This bra is definitely built for performance, which means it can be a little hard to pull on and off, but the trade-off is that once it’s on, it keeps everything in place even when you're sprinting for the finish line.

The North Face Mountain Athletics Bra: in the field 

I’ve been wearing this bra on every trail run as well as hiking the West Highland Way for about a month now and I’m really pleased with its performance. Not being especially busty, I actually don’t usually give a huge amount of thought to my sports bra and I’ve been running in old yoga bras for years that don’t actually offer much support, so I was interested to see how I’d like something so robust. 

The first thing that caught my eye was how nice it looks on. It’s super stylish and even if it’s going to be covered up with my running top, it’s still a nice detail. I got a small, which is my usual size, but when I first went to put it on it felt a little tight and I was afraid I’d got the wrong size. In reality, it fits perfectly and feels really good on, but I think the tightness is the price you pay for extra support in the field. I’m not sure how this will translate if you have a much bigger cup size, other than to say that I can’t imagine finding something more supportive than this, because you’ll lose that support with good stretch.

When I’m running, it is definitely really supportive but somehow manages to not be too tight as to restrict my movement or breathing, which is obviously super important. The FlashDry fabric definitely works well. Even with a good sweat going, I just get a little damp around my chest but I stay cool and it does dry quickly – not as fast as their Flight Series Weightless running top but I definitely don’t feel soggy after my run. Being synthetic material, it does get smelly faster, but not more so than my other synthetic bras.

When it's time to get it back off, I still have to do a little wrestling and I can hear the odd stitch giving way, so I’m not sure how it will hold up over time – it seems really robust otherwise – but right now, it still looks brand new.

Here’s how it performed:

Sizing

Don’t be fooled by it being a little hard to pull on and off, this fits true to size. 

Comfort 

Really comfortable thanks to soft jersey fabric, flat-locked seams and good coverage. 

Breathability 

FlashDry fabric keeps you dry and cool and dries fairly quickly. 

Durability 

Sturdy construction and design but the seams do pop a little when pulling it on and off. 

Here’s where we tested The North Face Mountain Athletics Bra:

The Strathblane Pipe Track is a classic fell running track just outside of Glasgow at the start of the Highlands that follows the route of the pipe that brings water from Loch Katrine to Glasgow, at the foot of the Campsies.

• How Advnture tests products

The best running tops are the ones you forget you're wearing. They do their job so well and feel so light that you can fully focus on what really matters during your run. Whether that's checking your split times on the roads, not getting lost on a trail run or not being blown off a mountain ridge on a sky run, your best running top will be with you for bead of sweat that leaves your body.

Performance is what sets the best running tops apart from standard t-shirts. Designed to feel soft against the skin, wick moisture away, keep you cool and to dry quickly, they enhance your running experience. Some even boast anti-microbial qualities, which means they repel sweaty odors.

To test the best running tops, we've laced up our trail running shoes and road running shoes and threw ourselves at adventurous training runs and spicy races. Every top in our selection is there on merit, thought we especially like the eco-creds and all round performance of the Patagonia Ridgeflow running T-shirt, which we think is the best running top money can buy.

We've found today's best prices for each top below, but if you're looking for a bargain then you might want to wait until Amazon Prime Day, which will take place on 11-12 July. We'll be rounding up all of this year's best Amazon Prime Day hiking deals, camping deals and Garmin watch deals, so stick with Advnture to make sure you get the best prices.

The best environmentally friendly running tops

Impressively made with entirely recycled poly material, and fair-trade sewn in Sri Lanka, Patagonia’s Ridge Flow running T-shirt is ideal for tackling trails throughout the summertime and in warmer climates. The jacquard patterned T has a mesh design, which allows air to flow through the garment constantly while you’re running, and any sweat that does build up is wicked away and very quickly dries. Unsurprisingly, given its mesh construction, we found the T-shirt is extremely lightweight and very comfortable to wear, with flat seams throughout. 

It also features HeiQ odor control, which prevented the build up of nasty smells on test. It won’t keep aggressive flora and fauna at bay, however, and the level of sun protection isn’t particularly high. Also, while the Patagonia logo is reflective, road runners going out amongst traffic after dark should be aware that there is no high-vis detailing on the back. Overall, though, this is an excellent, if slightly pricey, top for summer running. 

Read our full Patagonia Ridge Flow running T-shirt review

This relaxed-fit active-wear T-shirt from Norwegian brand Helly Hansen is extremely lightweight and on test we found it breathes well when worn during trail and road running outings. The Lifa Active poly material, which is 60% recycled, wicks sweat away beautifully, and the fabric has been infused with used coffee beans (a process HH call S.Café), which heightens the garment’s ability to protect the wearer from the harmful effects of the sun, giving the T-shirt a UPF sun protection rating of 50+. 

The coffee – which the brand claim will not wash out – also helps prevent the build up of bad odours caused by bacteria. While good for a range of outdoor pursuits, the lack of any reflective detail on the T-shirt is a shame for road runners who venture out after dark.

Read our full Helly Hansen Lifa Active Solen T-shirt review

The best trail running tops for long-distance runs

The perfect accompanying top half to the Jason Schlarb running shorts, this running tee has been designed for long outings in all sorts of conditions and on varying terrain. To perfect this garment, Boulder-based brand Ultimate Direction collaborated with Schlarb, an endurance athlete who has many ultra run achievements and accolades to his name.

So, what makes this tee good for big runs in tough conditions? Mostly the fact that it’s made half from merino wool and half from a partly plant-based fabric called sorona, all body-mapped into high sweat zones for optimal breathability. A magic material, the merino wicks moisture, provides warmth when required and keeps you cool when conditions are hot, doesn’t stink up easily because of its natural antibacterial properties, and feels lovely next to your skin. Merino’s many qualities do not, however, extend to longevity, so this is where the sorona fabric comes in, helping the tee last longer and keep its shape, so you can wear it for multiple marathon-plus escapades, or just for lots of training runs. 

On test we liked this tee. The flatlock seams, combined with the merino feel, do make it super comfortable, and the underarm gussets help with free arm movement. But, it is pricey, and we would like to see it offered in some different, lighter colors (the onyx is very dark and attracts and holds heat in the sun). It also gets pretty heavy once it’s wet – from sweat or rain – and takes a while to dry.

The best running tops for racing

The inov-8 Elite Base Layer running tee is exactly what most people are looking for when hunting for an all-purpose trail training and racing top. It’s lightweight, boasts breathable mesh panels right across the back and under each arm, and has been treated with an anti-stink treatment to prevent the build-up of friend-losing aromas. 

Despite being synthetic, we found the next-to-skin comfort levels are good, and we experienced no rubbing during testing, even wearing it straight out the packet for a 20-mile race. Being entirely synthetic, it dries super quickly, doesn’t get heavy when wet and still provides some level of thermal cover even when drenched – although the amount of mesh in the design does mean that this top is far from windproof, so it can be a bit breezy while you’re waiting on the start line (once you’re running, this turns into a real positive). 

While the design is quite loose, allowing for plenty of freedom of movement, and feels aimed more towards trail runners, there are reflective flourishes that will help drivers see you if you’re running on dark lanes and roads at night (although these are very small). And, of course, it’s made almost entirely with recycled polyester, which each top accounting for around eight 500ml PET bottles. 

It’s available in both long and short-sleeve versions, and the longie has thumb loops.

Read our full inov-8 Base Elite Short Sleeve Base Layer 3.0 review 

Pulling the Ultra S-Tech Trail Running t-shirt over your head instantly puts you in a racing frame of mind – the material mix and very close-fitting cut of this dynamic tee means it clings on tight to your torso, which is perfect if you’re in top fighting fitness form and want to avoid snagging on anything while running through the mountains and woods (but it leaves nowhere to hide if you’re carrying a few extra rations in the belly department). 

Despite the tightness, the material boasts four-way stretch, so we found it didn’t feel restrictive on test, even when we were hopping over rocks and tackling other trail obstacles. It’s unbelievably light, and the poly material barely takes on any moisture if you get caught out in the rain, so it won’t get any heavier no matter what the weather throws at you. 

The breathability levels are decent, with good mesh elements employed across the back and chest, and the design is seamless, which adds to comfort levels. On the downside, there is no recycled material content in this top, and it hasn’t been treated with an anti-pong/bacteria substance, so odors could accumulate after extended use. You need to be a bit careful how you wash it too – there’s not much room for it to get any tighter.

Read our full Dynafit Ultra S-Tech Shirt running top review

Firmly a running top for people who run hot, or who run regularly in warm conditions. This collaborative product, made by Italian brand Karpos with Polartec Delta as the main component, is comprised almost entirely of a mesh material, which meant it breathed like an absolute dream when we were working up a sweat on test, and we also found it wicks moisture away from the skin like a champion, but it did leave us shivering somewhat when we got caught out in less warm or more windy conditions. 

However, this is exactly how it’s been designed, and so long as you’re aware of this and wear it in appropriate scenarios, it works really well. 

It’s a real body hugger this one, which most faster runners will appreciate. There’s plenty of dynamic movement across the garment, but it can ride up a little bit under other layers or packs.  The fabric has been treated with polygiene to reduce the accumulation of pong, and we wore this top on sweaty runs all last summer, and can happily report that it remains relatively stink free. 

Read our full Karpos Moved Evo Jersey with Polartec running top review

Designed to offer a dynamic race fit, the Sabre hugs your torso and upper arms tight, so there’s no excess material to flap around in the wind or get caught on brambles and bushes when you’re out on the trails. On test, we found It didn’t feel restrictive, however, as the material has a reasonable amount of stretch – more than expected for a 100 per cent polyester garment. Weighing in at just 105g / 3.8oz, the Sabre barely feels like you’re wearing anything when you out it on. 

Equally functional for on-road or off-road running adventures, the tee comes in three pleasing colors and boasts reflective flourishes on the side and back, so car lights should pick you out (although, as with many designs, these are not very big). The rounded, low-profile merrow-stitched seams don’t rub or irritate during wear, and the material wicks moisture away when you sweat (and barely takes on any extra weight when it’s wet). 

The Apex PK fabric features polygiene permanent odor control – we will report on how this holds up after extended use. Sadly, there doesn’t appear to be any recycled fabric in the material mix, which is a bit of a let down. 

Read our full Montane Sabre running T-shirt review

The best running tops for value

As we have come to expect from the British brand Berghaus, this running top is a no-nonsense garment that does exactly what you want it to do, for a very reasonable price. No bells, no whistles, just a functional tee that’s ideal for running trails or roads. 

It’s made with entirely synthetic poly materials, which means it’s light, won’t absorb water (and therefore gain weight) if you’re running in rain, wicks sweat away excellently, and will still provide a level of thermal protection, even when wet. On test, we also found it dries very quickly. 

On the downside, such materials are not great for the planet – we’re pleased to see the fabric used is bluesign approved (although we’re not sure why, as there doesn’t appear to be any recycled content). The material has been given an anti-stink treatment, which is also a relief, since synthetics do tend to get a bit nose-wrinkly after a few good hard wears. 

We found the fit to be a bit on the baggy and generous side, with quite a lot of excess material. There are no reflective flashes on the top, which would have been nice safety addition for running on roads and lanes in the dark. 

Read our full Berghaus 24/7 Tech Tee Baselayer running top review

How we test running tops

We tested the best running t-shirts during road-running sessions, trail-scampering adventures and races in a range of climatic conditions, both with and without secondary layers and hydration packs.

How to choose the best running top

Everyone’s running needs are a little bit different, but here are some things to consider when buying a top to make sure you get the the best running t-shirt to suit your needs.

Materials

Probably the single biggest factor in any of the best running tops is what material to go for. The choice is typically between synthetic (which will be lightweight, quick-drying, good in wet weather and quite cheap, but are terrible for the environment, can be more abrasive to wear, and often start to pong) and a natural material, like merino wool or bamboo – both of which offer far better comfort, breathability and thermal performance levels than synthetics, and tend to stay nicer smelling. However, they do tend to cost a bit more and don’t last as long. A lot of brands use a mixture of synthetics and natural material, and this can offer the best of all worlds.

Design

A running top is a running top, right? Well, yes and no – not all tees are made equal. There are some obvious considerations to take into account, such as whether you want long or short sleeves, but other things to look at are mesh inclusions in sweaty areas (under the arms and across the back), which will really help with breathability, and extended back panels or good quality waist hems, which prevent tops riding up when you’re wearing a hydration pack. 

Fit

Some are looking for something baggy in the best running tops, others like their gear to be as streamlined and performance-focussed  as possible – it’s a completely subjective choice. Obviously, if a top is too loose, you may end up getting it snagged during trail runs.

Odor control

Synthetic tops in particular are prone to accumulating nasty sweat smells (which boils down to bacteria building up), so it’s worth seeking out tees that have been treated to deal with this.

Sustainability

Natural materials like merino wool and bamboo have a much lower carbon footprint, and are far less damaging to the environment all round than synthetics, not least because garments made with natural fibers are biodegradable at the end of their useful life, while synthetics t-shirts will be hanging out with the cockroaches long after the rest of us have become extinct. Increasingly, brands are using recycled plastic to make garments such as running tops – this isn’t perfect, because micro-plastics can be released during washing, but it is a step in the right direction. 

Safety features

Whether you run on trail or road, or a mixture, it’s likely you will find yourself jogging along a dark street or lane at some point, and a couple of reflective flourishes on the back and arms of your top can make the difference between a driver seeing you or not. These are always good inclusions. 

Price

The price of seemingly quite similar tops can vary an awful lot. If a top seems expensive, drill down into what it’s really offering you – including elements such as anti-odor treatments that should improve the usable lifespan of the garment – and make an informed decision. 

Black Diamond Long Sleeve Rhythm t-shirt: first impressions

Black Diamond claim their Long Sleeve Rhythm T-shirt is the world’s lightest ultimate high output, breathable layer and weighing in at just 104 grams, they can’t be too far off. This high quality base layer comes in a classic design but is made using Nuyarn merino wool technology which is touted as lighter, faster drying and 35% more stretchy than standard merino.

Sure enough, this soft, featherlight top is designed for movement, with a slim-but-not-tight fit, underarm panels to aid movement and a wide crew neck. It’s thin enough to fit under any mid layer in colder weather, makes the perfect breathable trail running top for when you’re covering a lot of ground in cooler temperatures and looks and works great for everyday use too. It holds up to a lot of action without needing to be washed after every adventure, so though it comes at a premium price, you’ll barely take it off once you pull it on.

Black Diamond Long Sleeve Rhythm t-shirt: on the slopes

Every few years, a base layer comes along that relegates all other base layers to the bottom of the pile for me. It’s either on my body, or folded at the very top of the drawer waiting to be worn out on my next adventure. The Black Diamond Long Sleeve Rhythm t-shirt definitely fits that bill for me and has honestly barely come off since it arrived.

I’ve worn this shirt on multiple hikes, trail runs, on my yoga mat and around the house. It’s soft and so lightweight I can barely feel it, and the classic fit isn’t too tight which, combined with good stretch, means I can move in any way I want without it catching or rubbing anywhere. I find the fit flattering enough that I frequently wear it with jeans around town, but it is slim enough that I can easily layer it under my fleece or down jacket, and it's long enough to comfortably tuck in.

For trail running, it definitely keeps me cool once I’m a few miles in and I couldn’t help but notice how quickly it dries. Rather than change as soon as I get back to the car like I do with my all-synthetic tops, this one stays on comfortably for the drive home. Because it’s made using natural materials, it can also hold up to quite a few hikes before it needs a wash, which is always a winner in my book.

The wide neck is really flattering and comfortable, however I think on a colder day I might opt for a top with a high zipped neck for snowshoeing if it was likely to be my only layer on the uphill, and it’s certainly on the pricey end of the spectrum, but for how versatile and durable it is, I think I’m getting my money’s worth on this one.

Here’s how it performed:

Sizing

True to size.

Fit

It’s not a skin tight top, but a flattering slim fit. Long enough to tuck in with a wide crew neck.

Comfort 

Soft, barely there feel to the fabric with added arm and underarm panels to support movement and no rubbing seams.

Temperature regulation 

Keeps you warm as a first layer in colder weather and keeps you cool once you start sweating on a trail run.

Breathability 

Ultra breathable, this shirt keeps you drier on the trail and dries quicker once you get back to the car or camp.

Durability 

So far, it’s standing up to the test of my adventures. The nylon/merino blends adds some stamina. Like any high end piece of gear, I recommend washing it on gentle, less frequently, and line drying to make it last longer.

Here’s where we tested the Black Diamond Long Sleeve Rhythm t-shirt:

From many high points in Glasgow, you can see the distinctive hill of Dumgoyne which is technically at the beginning of the Highlands. This volcanic plug makes a short but very steep hike on its own, or you can pair it with Earl’s Seat to the north for a longer hike or trail run.

Smartwool Intraknit Merino 200 bottoms: first impressions 

On the rack, these medium weight, minimalist bottoms are meant to keep you both warm and moving in cold weather. These slim-fitting pants can be worn under your hiking pants on cold expeditions, as sleepwear at camp or as leggings for hiking in fall, winter and spring. Combining the moisture-wicking capability of merino wool with the fast-drying time and durability of polyester, these bottoms are meant to keep you dry and comfortable no matter how technical the terrain.

The Intraknit Merino bottoms use 3D mapping technology to result in a snug, precise fit enhanced with ribbed knees that allows for total freedom of movement whether you’re curling up in your sleeping bag or scrambling up steep stuff. A high rise waist means no having to pull them up as you’re hiking, and protects you from rub from your hiking pants.

The medium weight means these bottoms don’t feel quite so soft and comfortable as some of Smartwool’s other garments, but once you wear them for a few minutes you won’t even notice them on your skin. These high quality bottoms come with a high price tag but it’s hard to find a better pair – if you take good care of them, they’ll be a staple in your cold weather kit for years to come.

Smartwool Intraknit Merino 200 bottoms: on the trails 

I’ve been testing these bottoms (along with their matching base layer) out for a while now as hiking pants and long underwear and true to Smartwool form, they stand up to pretty much any cold weather test. Smartwool have definitely perfected the art of thermoregulating fabric that wicks sweat away, dries quickly and leaves no stink.

Though I’d typically reserve them for long underwear under ski pants or sleepwear at camp, the sleek design can definitely serve as outer leggings on a hike. The high waist is definitely a big plus in terms of comfort and function – there’s nothing more annoying than having to hike your pants up every few steps. And the 3D knit and ribbed knees mean I can move in all directions without even noticing them – they’re almost better in that regard than some of my yoga pants.

The best way to wear these base layers is close to the skin, and I found these to run slightly large, so if you’re on the small side you might want to size down. Though they’re certainly not scratchy, I did notice that when I first pulled them on, they weren’t quite a soft as some of my other Smartwool garments, but once I wore them for a while I could barely feel them on my skin.

Finally, I still haven’t washed these and they smell fine, so they get full marks in the odor-resistant and durability categories. These bottoms don’t come cheap, but they’re high quality, long lasting and low maintenance.

Here’s how they performed:

Sizing

Slightly on the large side. If you tend towards the small end of your typical size and want these to be form fitting, size down. 

Fit

Slim fitting, high waist leggings. The company uses 3D knitting technology to produce what they call a “near custom fit” and I don’t know how they do it, but it works. 

Comfort 

Very comfortable seamless knit aids movement and any tiny scratchy wool sensation wears off after a few minutes. 

Temperature regulation 

These bottoms do the job they’re supposed to do: keep you warm in cold weather and cool you off when you start sweating by wicking the moisture away and drying quickly. The medium weight is good for very cold temperatures, but might be too warm under some conditions. 

Breathability 

Highly breathable composition and mesh ventilation. 

Durability 

Ribbed knees add durability and fantastic odor protection means you’ll barely ever wash these. They’ll last years. 

Here’s where we tested the Smartwool Intraknit Merino 200 bottoms: 

Ben Arthur, otherwise known as The Cobbler, is a distinctive peak at the head of Loch Lomond. The true summit requires some technical scrambling that many choose to miss.

Rab Mantle Tee: first impressions

At first glance, the Rab Mantle Tee is a robust and hard-wearing garment. It looks practical yet has an unflashy style that we found pleasing. It oozes the quiet confidence of a solid workhorse that won’t ask for much and never lets you down.

Built from lightweight, quick-drying and highly breathable polyester, the Rab Mantle Tee has soft, low-bulk seams to keep you comfortable on longer hikes. The classic round-neck t-shirt is treated with Polygiene, which permanently reduces odor-causing bacteria by more than 99%. As such, it’s a good choice for challenging activities or multi-day adventures. 

Rab pitches the Mantle Tee as ‘multi-purpose’, a phrase that often fills us with horror. However, it has all the hallmarks of a top that will do the distance on hikes, trail runs, bike rides, gym sessions, et al. So, in theory, a strong contender for one of the best men’s hiking shirts, but how did it perform when we put it to the test.

Rab Mantle Tee: on the trails 

The moment we pulled on the Rab Mantle Tee, it felt wonderfully well made. The stitching is absolutely cast-iron yet manages to feel discrete. Fit-wise, it's a classic t-shirt but not the kind that your body shape disappears into. It’s complimentary without looking overtly so. 

It’s a comfortable number, too. The robust, high-quality build feels reassuring. The only qualm comfort-wise is that the fabric might be a little coarse for some. 

On hikes and trail runs, the shirt performed like a dream. We loved it. Under exertion, it’s breathable and wicks moisture away quickly. Fast drying doesn't even begin to cut it. Wearing the Mantle Tee, we felt comfortable, dry and ready for action. It’s can also be easily used as part of your layering system (see our guide to hiking layers).

Due to the fit, comfort and look of this shirt, we found that it soon slipped into everyday life. Strictly for research purposes, we took this on a few sweaty outings without any washing and can vouch for the Polygiene treatment. As billed, this is most definitely a consummate all-rounder that will rise to any occasion. 

Columbia Newton Ridge: first impressions

The Columbia Newton Ridge is a lightweight hiking shirt that’s billed as ideal for the warmer months. Complete with Columbia’s own Omni-Wick technology, it promises high-performance wicking to quickly move moisture away from the skin and disperse it across the outer fabric for rapid evaporation.

The Newton Ridge has been designed with performance in mind. It has some nifty features including decent-sized breast pockets, a zip-up security pocket, well-tailored back vents and a sunglasses wipe. Columbia has strived to create a durable shirt that keeps you dry, using a blend of nylon and elastane,

At £55, it’s the most budget-friendly of all the button-up and collared offerings in our guide to the best hiking shirts and promises solid trail performance without breaking the bank.

Columbia Newton Ridge: on the trails 

When we slipped on the Newton Ridge, the first thing we noticed was how lightweight, spacious and breathable it felt. The fabric might not be the softest, but it almost seems to levitate over the skin allowing air to sweep through and cool.

As we climbed a steep and sustained woodland path in humid conditions, the shirt did a great job of keeping us cool. Without packs, the tailored back vents are able to get to work. As we started to perspire, the Newton Ridge rose to the occasion; effortlessly wicking moisture away, dispersing it efficiently and drying very quickly indeed. 

The Columbia Newton Ridge is, of course, a hot weather performer. In the latter stages of the hike, a misty rain descended and the afternoon cooled dramatically. It didn’t take long for us to feel chilly and reach for an outer layer. Then again, Columbia never promised insulation. 

We found the Newton Ridge to be quite a loose fit. While this inevitably helps with ventilation, you might consider sizing down if you're on the size border or prefer a tighter fit. Looks-wise, it’s very much the classic hiking shirt. If you’re looking to make a fashion statement on the trails, the Newton Ridge might lack chic. But if you want a hot weather workhorse, it’s a good choice.