Nike React Infinity Run Flyknit 4 review: a smooth ride, but stretch upper is an acquired taste

Nike's new ReactX midsole foam is pleasingly firm and stable, but the stretch of the knit upper can cause slipping at the heel

Woman's feet wearing Nike Infinity Run Flyknit 4 road running shoes - front view
(Image: © Future)

Advnture Verdict

A stable everyday training shoe with firmer foam and a distinct rocker shape for a smooth ride. The socklike woven upper is an acquired taste, and combined with the low cut you may notice some slipping at the back. They're solidly made though, and should see you through many miles of training rain or shine.


  • +

    Smooth ride from firm rocker sole

  • +

    Plenty of rubber on outsole for grip

  • +

    Plenty of room in midfoot and toebox

  • +

    Customizable colors


  • -

    Flyknit upper too yielding in places

  • -

    Some slipping at heel

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Nike React Infinity Run Flyknit 4: first impressions

The Nike React Infinity Run Flyknit 4 (also known as the Nike InfinityRN 4) is a highly cushioned and good-looking road running shoe. Its sock-like construction means the upper stretches to fit your foot, with different patterns used in different places to adjust the amount of 'give'. Looking at the upper, you'll see stripes of more densely woven material across the top of the foot, resulting in less stretch, while the end of the toebox is much more yielding.


• List price: $160/£155
• Weight (per shoe): 11.1oz/315g average mens'
• Drop: 9mm
• Materials: Flyknit woven upper, ReactX foam midsole, rubber outsole
• Colors: White/Light Lemon Twist/Volt/Black, Black/White/Black and more, plus custom options
• Compatibility: Everyday training

The fit is generous across the upper and toebox, but Nike recommends going up half a size to be on the safe side. There's also an extra wide fit model available if you need extra space.

The laces are thin with little stretch, and the tongue is only padded at the top, near your ankle. Ordinarily this might be a recipe for uncomfortable pressure on top of your foot, but the flexibility of the Flyknit material prevents any discomfort.

The InfinityRN 4 is the first shoe to use Nike's updated ReactX foam, which the company says gives 13% more energy return. It's shaped using injection molding rather than compression molding, which uses less energy and therefore reduces emissions from the manufacturing process. Basically, instead of taking a big piece of foam and squishing it down into the required shape, the new process involves taking a piece of hard material and 'foaming' it until it expands to fit the same space.

Nike Infinity Run Flyknit 4 road running shoes - front three quarter view

(Image credit: Future)

The resulting midsole is firm rather than bouncy, with a mild rocker shape better suited to everyday training than fast racing.

It's available in a decent range of colorways, but if you're not a fan of the standard options you can create your own custom design via the By You design tool on Nike's website.

Nike Infinity Run Flyknit 4: on the road

This review sample was provided by, and has been put through some serious miles during my training for the Manchester Marathon.

The overall feel is that of a stable daily trainer. The rocker sole unit has a generous stack height, but the new foam is on the firmer side and doesn't feel mushy at lower speeds, making this a comfortable and practical option for long, slow miles. However, the outsized heel and high drop are an acquired taste, meaning you might make contact with the ground sooner than you'd expect.

Woman's feet wearing Nike Infinity Run Flyknit 4 road running shoes - side view

(Image credit: Future)

The outsole has enough tread to provide good traction in wet weather. It was even reasonably grippy when a club run took an unexpected detour into a muddy wood, though if you're going to be running in the rain regularly I'd recommend opting for the Gore-Tex version. The standard FlyKnit material isn't water-resistant, although it does clean up well if you give it an accidental mud bath.

The material takes some getting used to though, being thicker and heavier than the mesh of most road runners. The variable stretch is a little strange, too. My big toes are a little upturned, and made visible 'poke' marks in the upper. From past experience I suspect that will be the first part of the shoe to wear out, but it could have been mitigated by continuing the bands of denser knit fabric further down towards the toe.

Woman's feet wearing Nike Infinity Run Flyknit 4 road running shoes - rear view

(Image credit: Future)

The insole is nice and smooth with quite minimal arch support, which is a refreshing change after testing the more aggressively designed Saucony Endorphin Shift 3.

The shoe is cut low around the ankle, and combined with the stretchy upper, this led to some slipping when I picked up the pace. Thankfully this was easily mitigated by making a heel lock, which the laces are long enough to accommodate.

Nike Infinity Run Flyknit 4 road running shoes - rear three quarter view

(Image credit: Future)
Cat Ellis

Cat is the editor of Advnture, She’s been a journalist for 15 years, and was fitness and wellbeing editor on TechRadar before joining the Advnture team in 2022. She’s a UK Athletics qualified run leader, and in her spare time enjoys nothing more than lacing up her shoes and hitting the roads and trails (the muddier, the better), usually wearing at least two sports watches.