Nike’s new “injury beaters” were a big surprise.


The new Nike React Infinity Run Flyknit shoes may have structure and injury prevention in mind, but our review paints a different picture.

Basics: Lots of foam, great aesthetics, and an innovative upper with multisport bells-and-whistles, but some odd comparisons from Nike
Pros: Lightweight for a trainer, big offset/rocker for those who like that feel
Cons: Abject lack of stability, narrow fit, issues with foot retention

Related reviews:
Unboxed: Nike React Infinity Run Flyknit
Hoka or Nike? We Compare Two Carbon-Plated Running Shoes
Video Review: New Hoka Carbon X Running Shoes
Hoka Arahi 3

Nike’s latest shoe, the React Infinity Run Flyknit may not generate as much titillating excitement as their (now) controversial “percent” line (the 4%, the NEXT%, and now the alien-like Alphafly NEXT%). There’s no carbon plate to draw federations’ possible ire, but triathletes should be excited about the concept behind the new shoe because they’re said to greatly reduce injury. Nike’s claim from their website:

To see if the shoe could help reduce injury compared to our motion control shoe, we commissioned a study through the British Columbia Sports Medicine Research Foundation where runners followed a 12-week variable training program ending in a half marathon. Based on the results, we think we’re on the right track: In testing*, the Nike React Infinity Run showed a 52 percent lower injury rate compared to the Nike Structure 22, our leading motion control shoe.

*The Nike React Infinity Run reduced running injuries by 52% compared to the Nike Air Zoom Structure 22 in a study of 226 men and women during a 12 week run training program (injury = missing 3 or more consecutive runs due to running related pain). Our study found that 30.3% of Nike Air Zoom Structure 22 runners experienced an injury but only 14.5% of Nike React Infinity Run runners experienced an injury.

Nike React Infinity Run: Comparing The Comparison

Now I’m not one to post information from brand websites word-for-word, but this is a pretty bold claim, and it does two things: First, it sets up the Nike React Infinity Run as a product that will significantly reduce injury—so the study says. If there was ANY product that actually reduced injury rates by 50%—heck even 20%—this would be nothing short of a miracle. While this review doesn’t have the scope to investigate that claim, we will address the second part of the above statement comparing this shoe to the Structure 22.

As a quick primer, the Structure 22 is a 10mm offset shoe that is considered one of Nike’s most stable pairs. This stability is accomplished via a sort of hard plastic heel cup that runs around the back of the foot and also extends down through the rear of the midsole. Though we don’t use the term as much any more, the Structure 22 is more like a motion control shoe.

Nike’s React Infinity Run is really nothing like that. There’s a lot of foam—in fact, Nike’s biggest reasoning for this pair’s injury prevention is quite literally “we put in more foam.” They claim 24 percent more foam than their Epic React 2, which is another strange comparison given that it’s a slightly lightweight trainer. The React Infinity Run has no sort of hard EVA or structure other than simply more foam to help with support duties—and it shows.

Nike React Infinity Run: A Pretty Picture

Without wasting too much time on the aesthetics of the React Infinity Run, it’s actually a really cool-looking shoe. I imagine this is something high schoolers/college runners would really be into—it’s got a really cool modern shape, and it’s got a very light, nice-feeling upper with a great seamless foot entry area. Out of the box, the React Infinity Run feels much lighter than you think it should be. It looks like a lot of shoe (remember all that foam?), but it doesn’t feel that way. The sewn-in tongue, minimal laces, rocker, and heel tab definitely scream “triathlete!!” But like anything, the proof is in how it performs out on the road.

Nike React Infinity Run: How It Feels

Right out of the box, it’s important to note that like many of Nike’s shoes, this is a very narrow last, so those with wide feet should probably take a pass. The React Infinity Run’s narrow last is further exaggerated by the literal height of the wearer’s foot off the ground, due to the mountain of foam beneath. Though no one would admit it publicly, it’s very clear that this shoe is a light jab at Hoka—lots of foam, a slight rocker, and claims to reduce injury—maybe in retribution for “borrowing” the carbon-plate concept in the recently released Hoka Carbon X. Who knows? While we’ll be doing a face off between Hoka’s Arahi 4 (the closest equivalent to the Structure 22 that Nike compared the React Infinity Run to) soon, it’s important to note that the great majority of Hoka’s shoes have a high amount of foam that cause the foot to rise up of the great, but they also have a very stable platform to help reduce movement from that height. This is where things on the React Infinity Run get a little weird.

Nike React Infinity Run: Riding High

After a few runs on this shoe, it’s very apparent that while the heavy amount of foam does cushion your legs from direct impact, the lack of structure, the height, and actually the upper/lacing system make this an almost tenuous shoe. Whereas Hoka is careful to make sure there’s a good wide platform underneath all of that foam (and usually no more than 5mm of drop), the React Infinity Run’s foam moves around a lot when you run. This can feel a little bit unnerving as the tiny muscles in your lower extremities work to keep you stable. In my runs, I could feel my IT bands and my inner leg muscles working to keep everything in line.

Nike React Infinity Run: The Upper Limits

The next part of this shoe that gave me pause was the upper. While I was very excited by the lightweight material, few lace, sewn-in tongue, and heel tab that made this look great for triathletes, unfortunately this combination also made for a lot of movement in certain types of socks. While the shoe itself was certainly the right size, I found my foot sliding around often in the slippery synthetic material, unable to properly tighten the few laces without crunching my normal-widthed foot inside the narrow last. This was most apparent with thinner, lightweight synthetic socks, and particularly on downhills. Though some may cry “You had the wrong size!” I’ve tested a lot of shoes in my day, and slightly too big or not, this has never been an issue for me. It also bears mention that my hopes of running sockless in this shoe were dashed by the rough material at the lip of the foot’s opening that rubbed and also put a slight amount of pressure on the sensitive achilles area.

Nike React Infinity Run: Conclusions, I’ve Got Some

There’s a lot of movement in the React Infinity Run. When you’re running efficiently and quickly, this is fine, but for those who are thinking this might be a good long, slow run-day shoe, you may want to reach for the Structure 22s or something similar. This was great for mid-length tempos, when I was really on my forefoot and on flat ground, but downhills felt almost sketchy and slow days just put a lot of confusion into the muscles on my legs, ankles, and feet that help keep this ageing building of an athlete from crashing down.

Now, there is a school of thought that says muscle confusion is a good thing—that weird feeling in my lower body could also have been those tiny muscles strengthening themselves and therefore reducing injury in the long run. But my fear is that people who require structure and support will reach for these shoes thinking they’ll be placed in a sort of framework that will prevent injuries based on biomechanical inefficiencies that can’t simply be “strengthened out.” While this isn’t a bad shoe necessarily, it’s very important that people are aware of what they’re getting into—particularly younger runners/triathletes who may be drawn in by the React Infinity Run’s aesthetics and big claims.