I’m not skeptical of the performance of that shoe, just their claims of what’s actually going on. I’ve read quite a bit of the material they’ve published. My hot take: all they’ve done is figured out is how to stabilize a shoe with a sole so tall it artificially increases your stride length without sacrificing energy efficiency to all that squishy foam. They can go on and on about foam formulations and the specifics of the carbon stabilizer…but at the end of the day longer stride = faster time.
They have successfully created an outsole that is fore-foot strike (similar to Newtons) first friendly at the same-time just as comfortable for heel strike first runners. The forefoot has a much larger strike zone than the heel which has a narrow extended strike zone.
Forefoot strike shoes are nothing new, neither are shoes that are good for both. Until I see a convincing case otherwise I stand by my hypothesis that 99% of the increase in performance (decrease in time) comes from artificially lengthening the user’s stride. Shove a stabilizer in a Hoka midsole and I bet you’d get the same boost in performance.
As a runner and a shoe designer, here’s my take (I’m no Kipchoge, but ran a 2:50 marathon Sunday so feel I’m somewhat qualified to talk on this) …
Since the first gen Nike 4% (the next% is gen 3), it has been the go to shoe for elites (putting aside the actual Elites have had a slightly different version than the $300 one available to the public). Records have been dropping for 3+ years now (There was some analysis a year or so ago post Berlin from New York Times I can’t find at the moment). Look at any major marathon and the majority of Elites are in these. They wouldn’t use them if they didn’t work. Even non-Nike athletes have been spotted rocking 4% with asics logos painted on…
I haven’t run in the next%, but race in the 4% Vapor Fly Flyknit. Was going to get the next%, but I prefer the Flyknit upper. I still may get the next% or wait for the commercialized version of the shoe Eliud ran in with 3 carbon plates and 2 zoom air bags if it ever comes to market. (Got a fresh pair of 4% already in a box anyhow for Boston next year). The difference between the Vapor Fly (4%/next %) and Zoom Fly is the foam. They both have the same carbon plate (and upper on the 4%- next% has different uppers). It’s not only the carbon plate, but indeed the rebound on the ZoomX foam in combo with the React foam. The weight difference alone is incredible and weight makes a difference over 26.2 miles (they say 1lb in body weight = 1 min in a marathon).
The mechanics of the shoe is not a forefoot strike thing. Just look at his stride. It’s pretty even/midfoot to be most efficient. The shoes feel like they literally push you forward when you run in them though are weird to walk in. That being said, a good stride while running is more about the vertical oscillation and cadence than stride length. You actually want to use your legs as pistons to pump up and down, and not extend your legs forward or you end up landing on the heel and braking. Very hard to actually do. I’ve been working with several coaches on this for years to improve.
There is actually very little stability in them. The next% in particular has a very narrow heel and pretty much zero heel stability and little forefoot stability but don’t feel as much stack height as they are. I think they have more drop now than previous.
The stiffness is not so much about stability but spring. Track spike likewise are super stiff and give the runner a push, but usually have zero stability (or even midsole on true spikes).
Material wise, I’m not sure the formula of the foams they use, but know there is a difference in “squish”/softness vs. rebound vs. compression set vs. weight. The ZoomX/React foams have a dialed in combo of the above, but it is certainly not just a soft HOKA like foam. Adidas boost (or the Sketchers knock off foam) TPU foam has a lot of rebound/bounce but my impression is bad compression set (gets squished down quickly and stays down). The Nike foam wear out (why they say these shoes only last ~200km vs. usually pair that lasts 400km), but in my experience on my second pair of 4% it’s as much the poor abrasion resistance as it is the compression set.
Kipchoge’s sub 2 hour marathon (1:59:40) was an incredible feat! It was certainly not a “race” and not able to be sanctioned (though it is certified I think) as World Record due to the condition, but the human effort involved is amazing. Just try running that pace… I’d be lucky to run it for 500m maybe as an all out interval. For sure the shoes and pacers and gear and course and weather contributed to the perfect conditions to break the barrier, but it is no less impressive!
Every brand out there now is chasing the carbon fiber benefit. HOKA already has the CarbonX. New Balance has one coming in the spring (already released the miler version 5200), Asics, etc. has been spotted on athletes testing them at Chicago and Berlin.
As an aside, an interesting discussion going on now in the sport and IAAF about what kind of advantage and technical benefits are allowed in shoes. There was some discussed about this when the first Nike 4% came out, but the latest shoe Kipchoge wore really pushing the boundaries. As I’d hope we all would want to do as designers!
damn, that spike is crazy! I’m too close to people there to say anything other than the amount of R&D and testing that goes into this stuff is pretty crazy. The facilities alone are unrivaled compared to anything else I’ve seen.
For sure I’d love to be a fly on the wall in the Nike Kitchen when these things were being designed and tested.
Funny thing to me as a designer and runner is how little both sides seem to talk and how little crossover there is. I have seen far too many shoes that seemed to have no design whatsoever with not much appeal to actual runners (or maybe marketing/sales just had final say), and ran in too many shoes that make me wonder if the designer has ever run.
I ran my first marathon in a shoe I designed (SKORA) and would love to do that again especially as I get faster. If anyone know of the next up and coming performance running brand, let me know. I’m actually working on launching an running footwear incubator project soon with prizing for the winning startup.
Nice to hear your insight Richard. I have seen far too many shoes not designed for my foot, taste, or running style in particular. I grew up running cross-country, track, 5k & 10k races so am more familiar than non runners. In high school I used to run 4 minute miles barefooted. My preference is zero drop or extremely minimal m.s/o.s support. In my experience, I think the problem with poor footwear design lies with sales/marketing/deadlines/budget. As a footwear designer, I am always trying to get away with more comfort, better materials and overall mass appeal. Ultimately unless you work at large footwear brand and have months and years to work out details, it’s tough to deliver a top notch performance specific sneaker.
Last week at the industry trade show The Running Event in Austin, Texas there was no shortage of running shoes featuring next generation foams with increased midsole thickness and carbon fiber plates. Saucony has one (or more), as do Asics, Brooks, Sketchers, New Balance, etc.
But here’s the thing - These shoes are already out of date…To beat the Nike at their own game, is impossible. Playing catch-up and following the same formula, but 2 years later, is a losing proposition…To truly design and develop the next generation of performance running shoes will take a “Big Idea”. So here’s some Big Ideas…