Nike ReactX Infinity Run 4 Review: A Big Step Forward

Introduction

The ReactX Infinity Run 4 is not the same shoe the Infinity line has been for its past three editions. The previous version was a solid daily trainer that some runners found decent rather than great, with complaints about a too-high arch and other fit issues. This fourth edition changes enough that it genuinely surprised us: it is simply a better shoe, and it earns its place as a comfortable, durable daily trainer with a supportive edge.

Upper and Fit

The shoe gets a brand new stretchy knit upper with a water-resistant liner. Nike says it is more accommodating in the forefoot than before, but it also runs a little short. Nike itself recommends going up a half size from your normal size, and in our testing the regular size did feel short, though the stretch of the knit mitigates some of that. If you like a snug, race-like fit, your regular size still works, with your toes right up against the top.

Normally a knit upper can feel sloppy, but this one locks the foot in well and the stretch works with the shoe rather than against it. The tongue is gusseted at the side, foam lines the collar for extra support around the heel and ankle, and there is a pull tab for easier entry. No heel lift was reported in testing.

ReactX Foam and Ride

The midsole uses ReactX, not an entirely new foam but a new way of making it. Previously the midsole was compression molded from a puck, with excess material cut away and wasted. Now the foam is injection molded straight into shape with no waste, a more sustainable process that Nike says also delivers 13 to 33 percent more energy return, and the performance is better than the previous model.

The feel is hard to pin down: it is not soft, but it is a bit; not squishy, but it has rebound. It reads as a dense foam that is also bouncy, slightly heavier than a light bouncy foam, and it delivers a comfortable ride. The rocker shape rolls smoothly through the stride and was a clear highlight.

Weight, Stack, and Outsole

More foam and more rubber mean more weight. The stack is now 39 mm in the heel and 30 mm in the forefoot, a 9 mm drop, and the outsole is a waffle design with extra rubber for traction and durability. A women’s size 7.5 came in at 9.6 oz (around 227 g), while a men’s size 10.5 came in over 12 oz, nearly 12.25 oz or 350 g.

The surprising part: it does not feel that heavy on the foot. The rocker keeps it rolling, and easy paces clicked along faster than in some lighter shoes. One possible critique is that there may be too much rubber on the bottom; an earlier lightweight model exposed more foam, and trimming some rubber could reduce weight. Still, durability looks strong: the original Infinity routinely delivered 400 to 600 miles, and this version looks capable of similar mileage.

Arch Support

Like most Nike shoes, there is fairly high arch support here, and you feel it when you slide your foot in. It is more forgiving than past Infinity iterations, smooth rather than that stabbing arch sensation. One tester found it helpful while dealing with a bothered foot, and another noted it made their Achilles happier. If you need some support in a shoe, this one delivers it without being aggressive.

Everyday Use and Comfort

This has been mainly an easy run and daily trainer shoe in testing. It also works well as a casual shoe and even a walking shoe thanks to its comfort. It is available now for $160, with shipping noted for mid-August.

Things to Consider Before Buying

Sizing is the biggest decision. Nike recommends going up a half size, and if you are between sizes or find your usual size slightly roomy, that is the safer bet. If your size already fits a little snug and you like that feel, staying true to size can work, but expect a short fit with toes near the top. The weight is also worth knowing upfront, even though the ride masks it well on foot.

Buying Advice

Do not be afraid of the weight. If you want a comfortable daily trainer that can take lots of miles and has that added support feature, this is an easy recommendation. One tester said they would recommend it over the Pegasus as a daily trainer and called it their favorite non-race Nike shoe this year. Both testers gave it a clear green light.

Conclusion

The ReactX Infinity Run 4 is a genuinely good shoe: comfortable, supportive, durable, and a clear improvement over its predecessor. Size up a half size if you want to follow Nike’s recommendation, stay true to size for a snug fit, and it should serve you well as an everyday trainer and beyond.