I got my first glimpse of the Vaporfly in a briefing at Nike headquarters in 2016, a few months before the now-infamous shoe was released. It had already been used in secret by both the men’s and women’s Olympic marathon champions a few months earlier, and lab testing had already demonstrated a four percent edge, on average, in running economy compared to the fastest racing shoes on the market. The question that leapt immediately to my mind was: What does the IAAF have to say about this?
It took a while to get a straight, on-the-record reply to that question, but eventually a Nike spokesperson gave me this: “The VaporFly Elite meets all IAAF product requirements and would not require any special inspection or approval.” In other words, the authorities didn’t even know about the shoe that was about to upend the sport.
In the three-plus years since then, a lot has changed. The IAAF, track and field’s governing body, is now known as World Athletics. The men’s and women’s world records for 10K, half-marathon, and marathon have been obliterated, along with countless national records and personal bests. And as of last week, as Martin Fritz Huber reported for Outside, a new set of rules has finally green-lighted existing versions of the Vaporfly once and for all but nixed the bizarre next-generation prototype that Eliud Kipchoge used to run an exhibition marathon in under two hours last fall. [Update, Feb. 13: Nike has since released details of Kipchoge’s prototype, and says the shoe does conform to the new rules.]
It’s one of those decisions that everyone seems to hate, as is the norm with compromises. I’m here neither to praise the new rules nor to bury them, but I do have a few thoughts on how we got here and why some of the dominant narratives about the Vaporfly are misleading.
The Alternate History
I was on a radio panel last week, before the decision was announced, with Reid Coolsaet, a two-time Canadian Olympic marathoner who let his long-time New Balance contract expire at the end of 2019 in order to chase a Tokyo qualifier in the Vaporfly. When the host asked whether the shoe should be banned—a move that would have let him stay with his long-time sponsor—Coolsaet strongly disagreed. “If they were to ban the current version right now,” he said, “it’d be quite unfair to anybody else still looking to meet that qualification standard.”
That, in essence, summarizes the bind that World Athletics was in. If they banned the Vaporfly effective immediately, they would screw over runners like Coolsaet; if they banned it retroactively, it would screw over those who had already notched qualifiers in it. By deploying the shoe without asking permission, Nike effectively checkmated World Athletics. That’s a common reading of the situation, and I think it’s essentially correct. But here’s the catch: I’m not sure things really would have turned out differently if they’d politely asked for permission.
Here’s how I imagine the conversation would have gone in that scenario, circa 2016:
Nike: We’ve got an amazing new shoe, and we want to make sure it follows the rules.
IAAF: Okay, shoot. Why is this shoe different from all other shoes?
Nike: Well, for starters, it has a full-length curved carbon-fiber plate embedded in the midsole.
IAAF: You mean like the one in Paul Tergat’s Fila Racers back in the early 2000s?
Nike: Sort of. But more like the one in Haile Gebrselassie’s world-record-setting Adidas ProPlate shoes. In fact, our new shoe was designed by a guy who did his PhD with the guy who designed Adidas’s carbon-fiber plate. In a side-by-side test, you’d have trouble guessing which plate was which.
IAAF: Okay, well, given that several other companies in addition to Fila and Adidas have produced shoes with carbon-fiber plates, we don’t see any reason to suddenly decide there’s something unfair about them.
Nike: Hang on, there’s another thing. The midsole is made from a new foam material we call ZoomX that’s both lighter and more resilient than previous foams, meaning it springs back with each stride to give you back more energy.
IAAF: You mean like Adidas’s Boost foam, which they boasted in 2013 had “the highest energy return in the running industry” and which produced a couple of marathon world records by Wilson Kipsang and Dennis Kimetto? Or the subsequent Boost Light, which combined high resilience with even lower weight?
Nike: Yeah, pretty much. Boost was about 10 percent better than previous midsole foams, returning about 75 percent of the energy you put in. ZoomX is another 10 percent better than Boost.
IAAF: Okay, that doesn’t seem like a deal-breaker. Anything else?
Nike: Yeah, the third key innovation is that we’re going to have a super-thick midsole, almost like platform shoes.
IAAF: Um... ever heard of Hoka?
Nike: Yeah, well, we’re not going to make it that thick. But close.
IAAF: Okay, then I think we’re good. Your three “innovations” sound like you’re just rehashing ideas that have been used in running shoes without controversy for years, if not decades.
Nike: But here’s the thing: we’ve got the mix just right. These shoes are way better than any previous shoe. They’ll improve your running economy by four percent. They’re going to annihilate every world record in the book!
IAAF: [sound of prolonged laughter in the background, then speakerphone is switched off and the laughter is disguised as a cough] Of course, of course. They sound wonderful. Put it all in the press release, I’m sure it’ll be a big hit. No worries on our end.
The Real Problem
I realize that scenario sounds a little ridiculous, given everything we now know about the Vaporfly’s impact. In fact, from the moment the shoe was released in 2017, our perception of it was skewed by the seemingly impossible promises made on its behalf. Nike had already announced its Breaking2 project, which aimed for a sub-two-hour marathon, but hadn’t yet revealed how they expected to achieve this goal. Then they unveiled the shoe.
The conclusion was obvious: any shoe that would slice three minutes off the marathon world record must be a cheat. It has a carbon-fiber plate in it? Then carbon-fiber plates are cheating. In a sense, it didn’t really matter what the technology was, because the premise followed from the conclusion. Any shoe that suddenly made an elite marathoner three minutes—or two minutes, or even one minute—faster must be cheating. How could it be otherwise?
And here’s where the problem started. Critics latched onto the carbon-fiber plate as clear evidence of cheating, and called for a ban. But that suggestion was easily dismissed, because of the decades-long history of carbon plates in shoes. Would Tergat’s and Gebrselassie’s performances be retroactively invalidated?
Personally, I was torn. I felt the shoes had created an unfair competitive situation. But I also felt that the obsession with the plates was misplaced, and claims of “spring-loaded shoes” and “mechanical doping” totally missed the point. The real problem was that the shoes worked too well. It wasn’t a case of cheating, but of innovation that had succeeded so much that it upset the delicate competitive balance at the elite level. It called for regulation rather than vilification.
That’s not what happened, though, and World Athletics found themselves caught between two vocal extremes: those arguing that the shoes were clearly and obviously illegal on technical grounds, and those arguing that the shoes were clearly and obviously legal based on technical precedents. In the glare of the headlights, they hesitated—and the longer they failed to act, the harder it became to contemplate any sort of ban.
The Turning Point
By mid-2019, a sort of détente seemed to be approaching. The Vaporfly was ubiquitous and dominant, but pros from many other companies were racing—and sometimes winning—in prototype versions of heavily cushioned, carbon-plate-equipped models. Pretty much every major shoe company had a Vaporfly competitor slated to hit the market in 2020. New shoe rules seemed increasingly unlikely.
Then, in October, Kipchoge ran his sub-two exhibition marathon in Vienna. Watching the livestream in the wee hours of the morning, I couldn’t take my eyes off his shoes. A new prototype reportedly dubbed the Alphafly, they no longer looked like anyone’s idea of a normal running shoe, with a massively thick sole and strange pods under the forefoot. While Nike still hasn’t released any details about them, wild rumors based on patent filings began to fly around about three different carbon fiber plates and yet another sudden leap in running economy.
The détente was over, because even if other shoe companies managed to match the original Vaporfly, Nike’s athletes would still be a step (or rather, several minutes) ahead—assuming the Alphafly wasn’t just a massive nose-tweak designed to spark outrage and make the Vaporfly seem reasonable, a possibility that seems unlikely but not entirely impossible.
It felt like a turning point. And I wasn’t the only one to think so: immediately after the race, the British Journal of Sports Medicine rushed an editorial online. The piece, which sports scientists Geoff Burns and Nicholas Tam had been working on long before Kipchoge’s race, called for a new limit on midsole thickness. Crucially, they argued that trying to regulate individual technical elements like the carbon-fiber plate wasn’t the way to go. Instead, the thickness limit would simply set parameters so that all companies would be working to innovate within the same constraints. They suggested setting the limits such that currently available shoes would be allowed, but future iterations—the Alphafly being the elephant in the room—would be nixed.
That’s essentially what World Athletics did last week. There are some additional details about multiple plates and track spikes. And they’ve also put a ban on the longstanding practice of having athletes racing in prototypes that haven’t yet been released to the public. While it’s simple in theory, there are a lot of moving parts to the new rules that will inevitably spark debate in the months to come.
Could World Athletics have handled this better? A quick and definitive set of rules in 2017 would have avoided many of these problems, and there were certainly lots of people calling for that at the time. In hindsight, they were right—but, in my view, for the wrong reasons. The new shoes aren’t spring-loaded, and they didn’t violate any obvious precedent in running shoe design. And the reasons matter if you want to formulate general rules rather than target specific shoes, otherwise you’re just treating a symptom and ignoring the underlying condition—which is bound to return.
Much as we might wish otherwise, technology has always played a role in the evolution of sport, and always will. Until last fall, the Vaporfly looked a lot like the klapskate, a hinged design that completely upended the speedskating world in the late 1990s. Dutch skaters were the first to adopt it, and they nabbed half the gold medals at the 1998 Olympics, while nine of the ten major world records fell that season. Skaters from other countries soon caught on, and within a year or two competitive equilibrium had returned: everyone was faster by a roughly equal amount.
But Kipchoge’s Alphafly prototype showed that we were reading from the wrong book. Instead, Vaporfly-style shoes now look more like the drag-reducing high-tech swimsuits that rocked the swimming world in 2008 and 2009, when world records were smashed more than 130 times. In that case, it wasn’t just one record-breaking suit: it was a wild free-for-all with new models repeatedly superseding the old ones. Swimming authorities imposed strict limits on the suits starting in 2010 to halt the arms race, much as World Athletics has now done.
Here’s the catch, though. When swimming’s new rules came into effect, there was a widespread sense that the age of world records was over for a long, long time. After all, the suits used to set every one of those records were now banned. But if you look at the 40 major men’s and women’s swimming records now, all but 12 of them have been set since 2010. Somehow, swimmers—or perhaps suits and pools—keep getting faster.
That’s the stat that popped to mind last month when Rhonex Kipruto, a 20-year-old rising star from Kenya, smashed the 10K road world record by running a sounds-like-a-typo time of 26:24 in Valencia, Spain. When I heard the time, I immediately assumed that the Vaporfly, or perhaps one of its imitators, had claimed another scalp. But it turned out that he was wearing a regular version of Adidas’s Takumi Sen, a traditional lightweight plate-less racing flat. The Vaporfly has changed everything, but perhaps at least some elements of the new landscape transcend the shoe. And that gives me a sliver of optimism that maybe, in time, someone will eventually run a sub-two-hour marathon with a shoe that conforms to the new rules. Then, for a refreshing change, we can all argue about drug testing instead.
For more Sweat Science, join me on Twitter and Facebook, sign up for the email newsletter, and check out my book Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance.
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Correction: This story has been updated to reflect the fact that Paul Tergat’s marathon world record was not set in Fila shoes. Outside regrets the error.