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12.4 oz. (353 g) for a US M10,
9.9 oz. (281 g) for a US W8
39 mm in the heel, 30 mm in the forefoot (9 mm drop)
Easy, stable miles
Bouncy ReactX midsole, wider platform, updated Flyknit upper
MEAGHAN: A little over three years ago, Nike introduced the React Infinity along with some bold claims (mainly that this new shoe would prevent all running injuries). I mean, the Swoosh got us good with the Vaporfly 4%, so I kind of understand why it went HAM with the injury prevention statements. All this to say, we’ve moved on to version four of this trainer, and the big message is less about injury and more about “sustainability-minded” practices.
A lot has changed. The Nike InfinityRN 4 now has a ReactX foam midsole, a familiar compound created with a simpler process (injection molding), so it reduces the carbon footprint and provides 13% more energy return. Nike also gave this one a little more juice, jacking up the foam to 39 mm in the heel and 30 mm in the forefoot for a 9 mm drop. Then, the design team added a waffle outsole, rocker design, and wider base for added stability. Basically, it’s a whole new shoe.
The Nike Infinity RN 4 also comes with a new Flyknit upper, midfoot support system, and a water-resistant liner. With all these updates, does it still feel like the Nike Infinity? Let’s dive in.
THOMAS: Meg already covered the concept behind the Infinity above, but I have my own story to share. I was lucky enough to head to Nike’s headquarters in Beaverton, Oregon, to get a whole day of education on the first version of this shoe, designed to keep runners off injured reserve. Nike’s months-long, grand campaign for the shoe was set to end with a half marathon in sunny Los Angeles in April 2020. The point of the half marathon was to show how athletes who trained in the shoe could make it to race day healthy and ready to compete. Unfortunately, Covid had other plans — no race for us (or anyone).
According to Nike’s research, a few design traits help runners avoid injuries. Studies done by Nike showed that shoes with softer, wider bases, added arch support, stabilized heels, and rockered soles could help keep runners injury-free. Altra and Xero are screaming into the void right now, but such is the fate of a natural running shoe brand.
Reading through these findings, however, I found myself wondering why more Nike shoes don’t subscribe to this formula. After all, you don’t really see Nike’s pro athletes using the Infinity. While the injury prevention angle was solid, the execution of the first three versions of the React Infinity Run needed some improvement. Nike seems to have made some big changes for the better. Let’s see if we can make it to infinity… and beyond.
ALDREN: For the last 3 years, the Infinity Run hailed as my workhorse, the shoe I got the bulk of my miles in. As we’ve seen the shoe evolve with different modifications in the upper, the key feature I liked about the shoe stayed mostly the same. A fat slab of React foam and plastic horseshoe wedge made for a stable combo that I ran well over thousands of miles in.
This is the first time we’re seeing an update to this midsole with the introduction of ReactX. That intrusive piece of plastic also seems to be missing, but as long as it’s stable, I can’t complain.
MEAGHAN: The Nike Infinity has always landed in the “meh” category for me, but it was clear this had changed on step-in. While there is apparent arch support (as there was in previous iterations) it now feels slightly less aggressive and a little more comfortable. The knit upper hugs the foot nicely (maybe a little too much, more on that later), and the foam around the collar adds to the comfort and overall structure.
As I’m deep in marathon training and the mileage has continued to increase, I found myself enjoying the extra bit of support these shoes provide, especially for my Achilles. The foam feels pretty dense but also responsive, and the wide base makes them super stable. This isn’t that “light and fast” feeling daily trainer, but it’s a solid cruiser that I’d use for recovery days, easy days, and even those medium-long runs.
THOMAS: I’m not a huge fan of stretch knit uppers. Typically, the material ends up sloppy or feels cheap, but Nike nailed this upper. The toe box is stretchy, while the saddle and heel counter holds your foot securely. Further, the padded gusset tongue feels luxurious with a short lace throat that helps get a good lockdown and creates a lot of space in the vamp. It all worked out really nicely for my narrow foot.
In the past, people complained about the arch bump being too intrusive, and the bump is still there. However, it feels gentler, more like a firmer pillow.
Meg talked about the injected ReactX in the opener. While the React formula is the same, the new injection mold technique brings something unique to the foam. When you land on ReactX, it’s medium soft. It doesn’t feel as soft as the Asics Gel-Nimbus 25, the upcoming New Balance 1080 v13, or the Hoka Bondi, but the comfort is right there with them. I enjoyed the rebound in the foam—the shoe bounds through your stride between the bounce and the rocker shape.
One thing everyone agreed on regarding the previous models was the longevity of the shoe. The React foam holds up, and with the solid rubber coverage on the outsole, this shoe will be with you for a long time.
ROBBE: Whenever I see sustainability in a shoe midsole, I know it’s probably going to suck. Luckily, the ReactX in this shoe is just “sustainability-minded,” so it still uses that same oil-based foam composition of the React that we know and love. The sustainability-minded part comes from the injection molding process, which has a 43% better carbon footprint than the standard React.
If you want true performance, this is a good thing, because the ReactX foam is the result of five years of researching, developing and testing in the Nike Sport Research Lab. Nike figure out a new formulation of injection molding that can produce a long-lasting, high-quality foam, while maintaining a lower carbon footprint. And it’s really good.
It’s soft on landing, but responsive on take-off, providing the best of both worlds. There’s plenty of comfort with the high stack height, but it rolls along without feeling like it’s sapping your energy. The knit upper is one of the best in recent memory, just perfectly done in my opinion (Nike is really good at making knit uppers). Lockdown is exceptional, all around comfort is in spades, and the wide platform provides the right amount of stability. Also, the generous layer of rubber will last a really long time.
It’s a bit heavy (more on that later), but it feels much lighter underfoot. And at $160 (still the same price as the original React Infinity), the value is undeniably there.
ALDREN: This is the softest the Infinity Run has ever felt. In the previous models, I felt that the midsole needed to go through a break-in period. For the first 50 miles, the Infinity was a firm, heavily rockered daily trainer, somewhat similar to the Saucony Endorphin Shift. After that, the midsole would start to soften up, similar to a Hoka Clifton level of cushioning — not a big jump, but still softer. That right there is the sweet spot for cushioning, and that’s where the InfinityRN 4 starts.
The ReactX feels great out of the box. It’s not too soft like Fresh Foam X or FlyteFoam Blast, which is probably for the better. If Nike went with ZoomX instead, the shoe would be treading in Invincible territory and get too unstable. This brings up the main reason why I’m on the review and begs the question, “Is this shoe in the stability category?” I’d say, “Sure.” This feels stable to me how the ASICS Superblast feels stable to me.
There’s a wide-based, rockered midsole that somewhat doesn’t allow my foot to pronate. When I started to run slower and sloppier, I could feel myself pronating more, but at a regular cruising pace, the shoe felt sturdy. I wouldn’t recommend this if you needed a heavier type of posting or support, but anyone in that mild pronation group would enjoy running in the InfinityRN 4.Shop Nike InfinityRN 4 - Men Shop Nike InfinityRN 4 - Women
MEAGHAN: While I think Nike did a good job with the knit upper, I found it to be a little too snug. The knit is super stretchy, but I still wanted a little extra room in the toe box. I would suggest (as does Nike, per their website) going up half a size in this one.
Also, this guy is not light. My US W7.5 came in at just under 10 oz(!), which might be the heaviest shoe I’ve received all year… With that said, the weight didn’t bother me much on the roads.
THOMAS: Normally, I wouldn’t even consider running in a shoe that weighs more than 12 oz. (340 g). Weirdly, this trainer does not feel like a heavy shoe. I never even considered it heavy before I weighed it, and my paces reflected a much lighter shoe. My easy runs are prescribed by my coach (Meaghan) between 8:50-9:44. Without thinking about it, most of my easy runs ended up between 8:30-9:20. Even so, I would love to see Nike knock some weight off the Infinity Run.
ROBBE: I don’t have much negative to say about this shoe. If anything, maybe that the knit upper is a bit warm. Obviously, it’s a little heavy but it’s not a dealbreaker whatsoever. I’m not a huge fan of the design, but something tells me I’ll change my mind once new colorways come around.
Oh, I guess one more thing– there’s a lot of “protect the planet” messaging around this shoe, revolving around reduced carbon footprint during the production process of the ReactX midsole (43% less than the previous React foam according to Nike). But as far as I can tell, the carbon reduction only applies to the midsole, which still uses the same oil-based foam it always has. And really– how much carbon is even used to blow up midsole foam? Not really sure. Also, notice how Nike uses the phrase “sustainability-minded,” not “sustainable.” Because it’s not sustainable, just like every other running shoe out there. I know every brand is trying to get their ESG score up, but making this a focal point of the marketing push is *just* a bit greenwashy.
ALDREN: As Meaghan mentioned, Nike recommends going up half a size. I did not. My little piggies were getting baked on my runs and had no air to breathe. There’s also this weird grip on the tongue that kinda gives me the heebie-jeebies when I touch it. It feels like overused velcro or a pencil gripper from 3rd grade.
The protruding area underneath the arch is dialed down a lot too. I, unlike many others, really enjoyed that part of the shoe. It caressed against my lack of an arch in previous models, and that feeling is gone. There’s still a slight lift there, but I want more of it.Shop Nike InfinityRN 4 - Men Shop Nike InfinityRN 4 - Women
MEAGHAN: The Nike InfinityRN 4 has been a nice surprise this summer. It came at just the right time in marathon training (mileage and intensity on the rise), where a little extra support is pretty desirable. Yes, it’s a bit heavy, but if you’re looking for that shoe that goes into auto-pilot on easy days, this is your guy.
THOMAS: I ended up enjoying every run in the InfinityRN 4. The cushioning feels terrific. I love the extra arch support, and the upper fit my foot like a glove. Meg described it best with the auto-pilot comment. I can zone out in this shoe, and the miles tick off.
ROBBE: I feel like this is the best non-racing Nike shoe right now. I was definitely a bit nervous about the weight, but the underfoot feel is that perfect combination of bounce and responsiveness. I was wondering how Nike was gonna follow up on the React, and now we have our answer. And it’s a good one.
ALDREN: I’m still a fan of the InfinityRN 4. It’s stable enough for me, and that’s all that matters. Nike did a great job with this ReactX midsole which really revived the Infinity Run this year. I’m sure the shoe will reach well above 500 miles with how durable React has been in the past and all the rubber underneath, so grabbing two or three pairs should keep you set for the year.
You can pick up the Nike InfinityRN 4 for $160 directly from Nike using the buttons below.
Meaghan signed up for her first marathon three weeks before the race, because it was $10 more than the half she planned to run. She learned everything in running the hard way. Now a USATF & UESCA certified run coach, she loves encouraging friends to go for big goals as she continues to chase faster times. She enjoys a hot cup of coffee, a cold martini, and making bagels for friends and family.More from Meaghan
As the founder of Believe in the Run, Thomas’s goal is to help runners pick the shoes and gear that will make their running experience the best that it can be.More from Thomas
Robbe is the senior editor of Believe in the Run. He loves going on weird routes through Baltimore, finding trash on the ground, and running with the Faster Bastards. At home in the city, but country at heart. Loves his two boys more than anything. Has the weakest ankles in the game.More from Robbe