On recent shoe tech development following the launch of the Nike Vaporfly

With recent speculation about a possible upcoming ban for some running shoe models from the Nike Vaporfly series I have written this post in an attempt to summarize what it's all about. It's a fascinating stories about marketing hype, shoes in disguise and performance benefits.

No one interested in the running shoe business in recent years have probably missed out on the debate following the launch of the Nike Vaporfly in association with the Breaking2 project in Monza, Italy in 2017. For those of you still unfamiliar with the Nike Vaporfly there's a ton of reading just a google moment away but here's a quick recap of what they are and what they do. Since the introduction of the Vaporfly with its carbon plate and extra thick midsole with Zoom X foam there's been a "giant leap for mankind" when it comes to development of marathon results and also world records.

Review the gap between the blue dots in this modelling of the marathon world record times (for men in these graphs). This leap summarizes the results progression and the Vaporfly debate pretty nicely.

The five fastest mens marathon in history have been ran since Berlin 2018 all using the Nike Vaporfly. From Jonathan Gault Twitter: @jgault13

Ever since the introduction of the Vaporfly and subsequent iterations, the Vaporfly Next% and the upcoming Nike Alpha Fly - on the feet of Eliud Kipchoge during his 1:59:40 INEOS Challenge in Vienna last  october (and perhaps on the feet of Nike sponsored athletes during the upcoming US olympic marathon trials taking place in Dallas in february 2020?) there's been an increasing debate about strictening regulations. A debate about unfair advantages began very soon after the launch of the shoes, already in march 2017. IAAF rules state (among other things) that any shoes used in competion must be reasonably available and must not provide an unfair advantage. Availability was an issue with the first version of the Vaporfly and initially also with the second generation with the Flyknit upper which, despite a premium price sold out immediately. With the introduction of the Vaporfly Next% they are now readily available.

Nike Vaporfly 4% Flyknit, the second generation of the record-breaking shoe.

The story however began and the shoes were taking part already in the olympic marathon in Rio in august 2016. They were just a bit disguised to make them appear with classic Nike colours as the already available and well known Nike Racing Flat Nike Zoom Streak 6.

Kipchoge and Rupp finishing the olympic marathon in Rio in Nike Vaporflys branded as Nike Zoom Streak. 

For reference purposes, Nike Zoom Streak 6

The unfair advantage is where it becomes interesting. Nike themselves as well as independant tests have verified the benefit in running economy to be on average 4% (ranging from 1,5 to over six percent), hence the name, for the Vaporfly. Since competing in running is not about having the lowest average heart rate, runners can sinply run faster with the same effort. For the Vaporfly Next% there isn't any corresponding data available in the public domain, to the best of my knowlegde.

I would recommend anyone interested in this topic to follow Ross Tucker or @scienceofsports, on Twitter, or listening to the Podcast The Real Science of Sports where this has been frequently discussed, e.g., in the episode "The Shoe That Broke Running" from 23 Oct 2019.

Who benefits and to what extent is still being debated. Maybe the benefit for recreational runners is even greater as compared to the pros? Also professional runners have different biomechanics and running economy so benefits may certainly vary within this cohort as well.

The debate regarding possible unfair advantes has taken unexpected and sometimes even quite humoristic turns over the last year when pro athletes sponsored by other brands such as Brooks and Asics have complained over the fact that prerequisites differ at the starting line, when they themselves have toed the line in majors like the Boston Marathon in prototype shoes which definitely violates the IAAF rule of availability! Another humoristic turn is for instance Adidas-sponsored athletes such as Herpassa Negassa and others competing in the Nike Vaporfly with clumsy hand-painting to cover the Nike Swoosh logo.

Adidas sponsored kenyan runner trying to hide the fact that ran in Nike Vaporfly. Did I mention that he ran a six minutes personal record of 2h03'40 in Dubai in january 2019...

Since the true advtantage on an individual basis is unknown, maybe it's a bold statement but what if Eliud Kipchoge is "just" a 2:03-guy with regular running shoes on his feet and his customized Vaporflys makes all the difference? Smashing the world record by 80 seconds when you are already the best marathon runner in history is not a minor thing. The same might be true for Kenenisa Bekele, who's marathon career has been a bit troubled by injuries but who came in only two seconds short of the world record in Berlin in september, wearing the Vaporfly Next%. These two runners are reportedly toeing the line side by side at the forthcoming London Marathon in april 2020. Will we see another astonishing breakthrough performance as they push each other into unknown territory, perhaps even breaking2, now on a record-elligible course without pace-setters, probably not though.

It is perheps less bold to say that maybe the ONLY reason why Eliud Kicphoge broke two hours in Vienna was the Alpha Flye shoe with it's extra thick foam and multiple carbonplates? The design and multiple components of the Alpha Fly is technologically unprecedented in the history of running shoes A detailed description of this shoe is available online, e.g., here. This shoe may have crossed the undefined line of unallowed technology and the debate has since focused on the thickness of the midsole and the possibilities of the IAAF coming up with a restriction there.

Nike Alpha Fly overview (prototype for the INEOS 1:59 Challenge)

Critics say it's too much focus on the shoes and not the performance of the runners but I don't consider that to be a valid argument any longer with recent devolpments. On the top elite level we are already playing a margins-matter-game optimizing and tweaking the final few percentages and shoes that may alter performance as much as four percent or even more has to be debated. At no other point in the development of running shoes has there been a comparable performance paradigm shift as since the introduction of the Nike Vaporfly series.

The mega success of the Vaporfly has not left competitors paralyzed although they are indeed all late to the party. Saucony is releasing the top line carbon plated Endorphin Pro this season, seen as a prototype in the 2019 New York City Marathon on the feet of Saucony top runner American Jared Ward. Brooks is soon to follow with the Hyperion Elite and an Asics Prototype based on their newest Metaride/Glideride platform has been seen as well but competitors all face a challenge with the lead that Nike has established since almost three years now.

Asics stock market price by the way, took a hit recently when an overvwhelminly majority of the top runners taking place in one of Japan's most-watched road races, the Hakone Ekiden relay, choose to run in Nike Vaporfly instead of domestic brands like Asics and Mizuno which traditionally has a stronge local presence at races in their home markets.

The maximalism era that took over from the Born to Run-inspired minimalism movement is now making its way into the racing segments, making the term racing flats, redundant.

My personal experience of these shoes is perhaps not of interest but they do definitely help me to run faster, although I don't dare to put a number on it. I have a pair of the Vapofly 4% Flyknit and tempo runs are consistently run at a much faster pace than I intended, at the same effort. I have ran my fastest ever 5k on road in these shoes, ten seconds faster than my 5k-track PR. I have used them for racing a marathon and two half marathons so far resulting in my second fastest marathon (although three minutes away from the five year old PR when I was in a much better shape, and used traditional racing flats). I DNF'ed one of the half marathons due to calf injury, something I don't particularly blame the shoes for, but rather a pre-race training overload but the debate whether they also speed up recovery post race is still a questionmark, for me. I find that they leave my thighs less sore after a race or tough workout. On the other hand the lack of stability in the upper takes a little bit of toll on my feet and lower legs instead.

I guess there will be some kind of new regulations coming into place. The Nike Alpha Fly might be too much of a technological monster-shoe and there will perhaps be limitations implemented on the number of plates allowed in a midsole or the allowed thickness of the midsole, at some point going forward. A way forward as suggested by Ross Tucker already may be to set the limit of the midsole to 36 mm, which happens to be the midsole thickness of the Vaporfly Next% to protect the legitimacy of the world records. Currently the mens world record have been set using the Vaporfly Elite (Eliud Kipchoge Berlin 2018, customized shoe) while the womens world record was ran with the Vaporfly Next% (Brigid Koskei, Chicago 2019, unknown if customized or commercially available shoe). This would then ban the Alpha Fly and further "absurdity" in midsole thickening as Tucker states it. But perhaps even the Next% will be banned as recently stated in this article while still allowing the Vaporfly 4%. Where the line will be drawn, if at all, remains to be seen. My guess right now is that we won't see any Nike Alpha Fly-shoes on the starting line of the olympic marathon in Sapporo, Japan this august.

The 2:14-performance of Brigid Kosgei, actually ran the day after Eliud Kipchoge ran 1:59:41 in Vienna but getting only a fraction of the same attention when in fact it's the same magnitude of change and paradigm shift taking place, is perhaps the subject of a different blog post. Brigid Kosgei, associated with a manager involved in doping speculation for several years, completely smashed Paula Radcliffe's phenomenal, and to some extent already questioned world record, 2:15 from London 2003. A time no one has come even close for years, the closest someone's been is 2:17:01 by Kenyas Mary Keitany. A 2:17-marathon has also been accomplished by Chepngetich, Degafa and Dibaba (2:17:07. 2:17:41 and 2:17:56 respectively) but the difference between 2:17 and 2:14 is greater than between 2:01:39 (current mens world record set by Kipchoge) and the 1:59:41 in Vienna, or between the Kimetto world record 2:02:58 set in Berlin in the pre-Vaporfly era using Adidas Adizero Adios and 2:01:39). Therefore, the amazing record set by Kosgei leaves me with very little excitement or interest as it is such an anomaly as compared to other results in the womens marathon.

One of the key attractive features of running is its low-tech nature, its simplicity and availability but on the other hand we also see the use of altitude tents, low gravity treadmills, power meters and the use of technology is no longer limited to shoes only. While it is often not desirable to try to inhibit technological advances, sometimes when leaps are too big there might be a neccessity to intervene nevertheless, or at least to take a step back and review the situation, which is what is currently taking place, and that I think is a thing for the benefit of the sport of running, in the long term.

Thank you for taking the time to read this quite long text! As always, thoughts are always welcome!

Edit, the IAAF decision was published today on Jan 31. Read more here:

https://www.worldathletics.org/news/press-releases/modified-rules-shoes

This means that the Nike Alpha Fly that Kipchoge used to run 1:59 in Wienna will not be allowed, provided that it had multiple plates. Nike however, might have been prepared for this outcome and it remains to be seen if an Alpha Fly with only one plate and a lower stack height will be commercialized. For other brands it means that they may need to rush their launch of their top models since the shoes have to be available months before the 2020 olympics.

Edit note 2, Nike has now announced a "legal" (presumably still a prototype) Nike Air Zoom Next% AlphaFly with only one full lenght carbon plate and an stack height, meeting the IAAF criteria, of course. The shoe however must be available for sale from 30 april to be allowed to be used at the olympics but a possible launch date has been reported to be as early as end of february 2020, at a price point that is currently not known. Read more here:

https://www.runnersworld.com/uk/gear/shoes/a30777696/nike-alphafly/

A shoe for the Tokyo olympics marathon podium. The Nike Air Zoom Next% AlphaFly.

This is the end of the story, for now. With the new IAAF-rules being so "liberal" there's a new perspective on performance in running that is here to stay for a long period of time. I've referred to professor Ross Tucker above in this text, he has published an article that summarizes this comprehensively, you find it here.