When Nike first introduced the React Infinity back in early 2020, the company claimed it would prevent injuries. That’s a bold claim. And while it may have been proven in a few small, Nike-backed studies, there’s no specific evidence that the type of running shoe you wear can prevent injuries, according to a more recent meta-analysis of existing studies. But we will say this: We’ve run every iteration of the React Infinity nearly into the ground because it’s such a comfortable, multi-tasking shoe.
However, as the company’s most sustainable version of the shoe yet, the Nike InfinityRN 4 is a deviation from the past. It’s built around a brand-new foam that not only delivers a higher energy return for runners, but also has a lower carbon footprint to make you feel better about buying yet another pair of running shoes. (That doesn’t mean it’s a wholly “sustainable” shoe, FYI, just that the manufacturing process is a little better for the environment.) Is it worth the $160 investment? We put it to the test while training for the New York City Marathon.
The newest Nike InfinityRN 4 is the company's most sustainable shoe yet. Plus, a new foam promises higher energy return for all types of runners.
What we liked about it
The new ReactX midsole
The big hook for the InfinityRN 4 is the debut of Nike’s sustainably minded ReactX midsole foam. Instead of traditional compression molding, the ReactX foam undergoes an injection process. And the only thing you need to know about that is that you, the wearer, get a much higher energy return (i.e. more bounce with every step). In fact, Nike says ReactX increases energy return by 13%.
The other benefit of the injection process is it cuts down the carbon footprint in a pair of midsoles by at least 43%, according to Nike, due to reduced energy in the manufacturing process. We didn’t lab test these shoes, so we can’t confirm the energy return percentage, but they definitely felt springier than our Infinity Run 3 (with cushioning more akin to the Invincible 3) on one hour-long easy run — and significantly more responsive than the brand’s previous “most sustainably minded shoe,” the Nike Air Zoom Alphafly Next Nature, which felt like a brick.
It feels really secure
Nike markets the Pegasus 40 as the workhorse of their running lineup, but we’ve always gravitated to the Infinity as our do-anything shoe thanks to its stability, reliability and durability. The InfinityRN 4 improves on all of the above. It’s equipped with an all-new Nike Flyknit upper that’s flexible where you want it to be and secure where you need it to be (plus, the fabric uses an average of 60% less waste than traditional footwear-upper manufacturing). This is a shoe you don’t need to break in; it’s comfortable right out the box. While it was snug enough to eliminate any excess movement of the foot (especially around the heel), we did notice the increased volume in the toe — an appreciated update, since Nikes tend to run narrow. There’s also a wide base, and plenty of support underfoot; while the previous version had 30 millimeters of foam under the heel and 22 under the forefoot, this has 39 under the heel and 30 under the forefoot. That’s a big jump, and one that’s right in line with the current maximal cushioning trend.
What we didn’t like about it
The sizing is a little off
While we found the InfinityRN 4 to be true to size (we wear a women’s size 10), Nike does recommend going up half a size. Shoe fit is hard enough as it is, and we find it frustrating when a shoe doesn’t conform to standard sizing. Fit and comfort are the number one factor to consider when it comes to running shoes, so order two sizes if you’re not 100% sure which will feel best.
The “sustainability” angle is a bit misleading
It’s awesome that a huge shoe company like Nike is adapting their most popular running shoes to be more environmentally friendly, but in the case of the InfinityRN 4, that’s only referring to the injection molding process. This is not a recyclable shoe à la On’s subscription-based Cyclon or Salomon’s Index.01; it’s also not carbon-neutral, like Brooks’ bestselling Ghost 15. That’s not necessarily a bad thing, but this isn’t exactly a groundbreaking move in terms of sustainability.
How it compares
We’ve always liked the Infinity because it’s a great multitasking shoe: It can handle long runs, easy runs, even workouts (it’s a great shoe to travel with, especially if you don’t want to bring multiple pairs of sneakers for walking and running). We’d liken it to the recently revamped Asics Gel-Nimbus 25 or the upcoming New Balance 1080 v13 as a comfortable daily trainer that can also pick up the pace.
Bottom line
After spending a couple weeks running in this shoe, we definitely think the Nike InfinityRN 4 is worth the investment. OK, you’re not totally saving the environment by purchasing it, but it’s also not a slapdash attempt to appease sustainably minded runners and those with performance goals. For us, this is a shoe we can always count on, and the addition of the ReactX foam only put more pep in our step.
