Research suggests the Vaporfly soles give runners more energetic efficiency: at least a 4% boost over shoes from competing brands.
Vaporflys are so advantageous that some runners sponsored by other brands have taken to wearing the shoes in secret.
They black out the shoes with permanent marker so the Nike logo and neon colors aren't visible.
Eliud Kipchoge ran the first sub-two-hour marathon last October in Vienna. That same month, Brigid Kosgei broke the women's marathon record in Chicago. Then in November, Geoffrey Kamworor won the New York City Marathon for the second time in three years.
The three achievements had a crucial factor in common: All the runners were wearing Nike Vaporfly shoes.
Vaporflys (and prototypes of them) have been involved in nearly every major running victory and milestone since 2016, and for good reason: Research suggests the design of their soles gives runners at least 4% more energetic efficiency over shoes from competing brands.
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"The runner runs the race, but the shoe enables him or her to run it faster for the same effort or ability," Geoff Burns, a kinesiology researcher and pro runner, told Business Insider of Vaporflys. "So for two athletes of equal ability on race day, the one with the shoes is going to beat the one without the shoes."
That has led some athletes sponsored by companies other than Nike to don Vaporflys in secret. In at least three competitions, non-Nike runners have worn "blacked-out" Vaporflys: shoes covered in black permanent marker to make it difficult to spot the Nike swoosh.
Tommy Rivers Puzey was one of them.
"I realized there was a new technology creating an advantage, and if you weren't willing to jump on board, you would be left behind," he told Business Insider.
Puzey wore blacked-out Nikes during the California International Marathon in December. At the time, he was in between a terminated sponsorship contract with Altra and a new one with Craft. He ended his agreement with Altra amicably, he said, because the company wouldn't let him wear Vaporflys.
"I loved that company, but in terms of performance on race day, the Nike runners were driving a race car and we were driving a Mack truck," he said.
Runners are blacking out Vaporflys
Kipchoge, who broke the men's marathon record two years ago, as well as Kamworor and Kosgei, are all Nike-backed runners. Through such sponsorships, an athlete typically receives equipment and often money in exchange for agreeing to use the company's products exclusively.
But in the case of Vaporflys, a couple of runners sponsored by brands like New Balance and Under Armour found themselves at a disadvantage — so some put on Nikes instead and attempted to hide it.
Photos from the 2019 KBC Dublin Marathon show the runner Stephen Scullion in blacked-out Nikes — they're visible in an image on the Instagram account "Protosofthegram," which tracks "running shoes, developments, and prototypes," as well as in a shot from an event photographer.
Scullion is sponsored by Under Armour; on his own Instagram profile, all photos from that Dublin race have the shoes cropped out. He came in second there, crossing the finish line in two hours and 12 minutes.
Scullion did not respond to a request for comment for this story, but Under Armour told Business Insider that he had begun testing one of the company's own marathon racing-shoe prototypes.
Another runner, Joaquín Arbe, was also spotted in blacked-out Vaporflys at the Buenos Aires half marathon in August 2019, though he was sponsored by New Balance at the time. A photo posted by Protosofthegram reveals the Vaporflys' sharp heel on his foot, as does another by the Infobae photographer Franco Fafasuli.
Arbe was the fastest South American runner to finish that race.
Afterward, Arbe said he might switch sponsors. "We are closing the negotiation with Nike," he told Radio 5. "I already ran with their clothing."
Indeed, at the Buenos Aires marathon a month later, he didn't bother to black out his Vaporflys, wearing them in all their neon-green glory. Arbe came in sixth, clocking a personal-best time of two hours and 11 minutes.
New Balance confirmed that Arbe was no longer one of its sponsored athletes but declined to comment on his blacked-out Nikes. Arbe did not respond to requests for comment, but his Instagram page shows he has been running in Nike products since November as he trains for the Tokyo Olympics.
'Athletes have to go for the best product'
Puzey said he didn't think he could qualify for the Olympic marathon trials without Vaporflys. An independent study found that the shoes improved an athlete's running economy by 4.2% compared with Adidas Adizero Adios 3 shoes. Alphaflys, the next iteration of Nike's Vaporflys, likely give runners a similar edge: Kipchoge wore an early version of those when he broke the two-hour marathon mark. Alphaflys became available to the public in July.
Over marathon-length distances, a 4% improvement is a lot — for athletes like Kipchoge and Kosgei, it could be the difference between setting a world record and falling short. For Puzey, it could help improve his time by 3 1/2 to 5 minutes.
Puzey said it could easily take up to two years to improve a runner's efficiency by about 1.5% — and that requires "hard training, strict diets, massages, naps, and playing with fire in terms of your body breaking down."
That's why he asked Altra if the company would be comfortable with his wearing Nikes.
"I don't ever want to be in a position where I feel like there's a superior product on the market and the company I represent wants me to have to choose between representing them or being the best I could be," Puzey said.
In the California race, he added, he blacked out the Vaporflys because he "didn't want it to look as though I was representing Nike."
His new sponsor, Craft, is OK with his jumping ship when it comes to footwear.
Eric Schenker, Craft Sports' CEO, told Business Insider that's in part because the company was "new to the footwear game." So its approach for now is to let Puzey "wear where whatever he wants while we try and catch up."
"Athletes have to go for the best product," Schenker said, but added: "If I was another brand that had been making shoes for a long time, I'd be pissed."
Why Vaporflys work so well
The Vaporflys' secret is their soles, which fuse a foam layer and carbon-fiber plate. The plate is curved under the front of the shoes, which helps quickly rock runners from their heels to toes as they land and push off again. Every aspect of that design is meant to minimize how much energy is lost per footfall.
Vaporflys also have a distinctive shape. Whereas most shoes have a somewhat rectangular, boxy profile, the Nikes look more like a tapered spearhead. Less than 4 inches at their widest point, Vaporflys have a razor-like heel.
The shoes' upper material is almost paper-thin — it's made of a water-wicking fabric called Vaporweave that Nike manufactures in a neon pallet.
"There's a reason Nike made their shoes bright green and pink — you can't hide that you're wearing them," Puzey said. "You can spot people running in them from a mile away."
Still, the see-through fabric is conducive to being scribbled over in permanent marker.
"That's the way you lose a contract, trying to deceive people and blacking a shoe out," Puzey said. "Some people have gone so far as to take the upper part of their shoe and have it sewn onto the sole of another shoe."
How other companies are trying to compete with Nike
Puzey said he raced up to 50 times a year, all while running a physical-therapy practice in Flagstaff, Arizona. Prize money from running helps him support his family: his wife, Stephanie, and their three daughters.
"You put a lot of pressure on making sure you don't come home empty-handed," he said.
That's why he was so quick to notice the Vaporfly trend.
"People I'd competed against in the past, who I was noticeably faster than, were now finishing ahead of me," Puzey said.
World Athletics — the organization that governs international track-and-field events — noticed, too. The group launched an investigation to determine whether Vaporflys conferred an unfair advantage. But after months of deliberating, it came back with an answer in January: No.
That left competitors determined to hurry up and innovate.
Other athletic brands have come out with shoes whose soles use a foam and carbon-fiber combo like the Vaporflys — the list includes the New Balance Fuel Cell 5280, the Brooks Hyperion Elite, the Under Armour Hovr Machina, and the Hoka Carbon X.
But no independent studies show any of those shoes to be equal to Vaporflys.
"Nike put the white rabbit out for other shoe companies to chase," Puzey said.
Representatives from six brands told Business Insider they either had already made or were working on developing products to ensure their athletes could compete with Nike.
An Under Armour representative, for example, said the company was working with athletes like Scullion to "develop best-in-class products for their respective sport." Colin Ingram, the director of product at Hoka, said he wasn't "super worried" about blacked-out Vaporfly shoes.
"Everyone's seen the pictures of this masked approach, but our athletes are fairly confident in what they're doing and the products they can run in," Ingram said.
Schenker, however, said catching up with Nike was at the forefront of designers' minds at Craft.
"We aspire for Tommy to not have to wear blacked-out Nikes — that's going to be our new brand motto," he said.
Though the Olympics and nearly all marathons have been postponed until 2021 because of the coronavirus pandemic, Puzey is off the running circuit for a different reason: He was hospitalized with lung cancer last month.
He also tore his meniscus and hamstring in January, during the 23rd mile of the Houston marathon — the last opportunity for runners to achieve the requisite time to qualify for the Olympic trials in Atlanta. Until his injury, Puzey said, he was pacing for a marathon time two minutes faster than what he needed to qualify.
"It was the most comfortable I've ever felt at that stage of a marathon," he said, adding: "I think that if my trajectory would have continued, I hadn't gotten injured, and I continued to build on my fitness through Atlanta, I think I could've run 2:15 and maybe even high 2:14 in those Nikes."
That would have been three minutes faster than he'd ever run a marathon before.
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