The shoes feature a stiff sole plate and an air pocket under the ball of the foot, as well as using a new kind of foam which is softer, returns more energy and is very lightweight, said Geoff Burns, a sports scientist at the University of Michigan.

“That combination has been really transformative,” Burns told CNN on Friday.

Karsten Warholm (second from left) criticized the Nike shoe design.

First seen in road running shoes a few years ago, the technology has since made its way into track shoes, too.

Its introduction drove down road running race times significantly, and while its effect on the track is less pronounced, it still gives an estimated 1% to 2% advantage for middle- and long-distance runners, said Burns.

“How much that moves the dial in a sprint event, that’s a big unknown right now,” he said.

While there is no data on the effects of the spikes in shorter races, 400 meter champion Warholm criticized the Nike shoes worn by rival Rai Benjamin and raised concerns about their potential impact on the sport.

“He had his things in between his shoes, which I hate by the way,” said Warholm, who wears Puma spikes that have been developed with the help of racing car manufacturer Mercedes.

“If you want cushioning, you can put a mattress there, but if you put a trampoline there, I think it’s bullsh*t and I think it takes credibility away from our sport,” said Warholm.

CNN has contacted Nike and the International Olympic Committee for comment, while Benjamin, who came second to Warholm in the men’s 400 meter hurdles, credited the athletes themselves, rather than technology.

“People say it’s the track … it’s the shoes. I would wear different shoes and still run fast, it doesn’t really matter,” he said. “There’s some efficiency in the shoe, don’t get me wrong, and it’s nice to have a good track.

USA's Sydney Mclaughlin (R) emphasized the speed of the track.

“But no one in history is going to go out there and do what we did just now, ever. I don’t care who you are.”

Nonetheless, some critics argue that technological developments are akin to taking performance-enhancing drugs. “We’re talking about performance integrity,” sports scientist Ross Tucker told CNN in 2019 as he reflected on developments in shoe technology.

“These shoes create the same problems that doping throws up.”

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Others, like Burns, point to the fact that the shoes don’t break any rules.

“It’s not mechanical doping in the sense that all of these shoes are legal,” he said. “They’re not cheating.”

But the technology does throw up thorny questions when it comes to comparing today’s athletes with past record holders.

Earlier this year, men’s 100 meter world record holder Usain Bolt said he wasn’t worried should his records eventually be broken with the help of such technology, rather than pure physical prowess.

“The fact that everyone will know why, then it doesn’t bother me,” Bolt told CNN in March. “As I said, I’m happy to be the fastest man in the world, but it was always the gold medals that really mattered to me because that’s how you really prove yourself.”

‘More rebound’

While Warholm acknowledged that the athletes are pushing each other to faster times, the 25-year-old Norwegian also referenced what he called a “great track.”

The surface is supplied by Italian manufacturer Mondo, which said its main objective “is to maximize the speed of athletes and improve their performance.”

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According to World Athletics and Mondo, more than 280 world records had been established on the company’s tracks prior to the Tokyo Olympics.

Dalilah Muhammad, who won silver in the women’s 400 meter hurdles for Team USA, is one of a number of athletes who noted how the track had affected her performance.

“It is a really fast track, and it boils down to that. You can kind of tell how fast the track is by how easily you are making your steps between the hurdles,” she said. “It was spot on, at every hurdle. I was able to do a 14-step pattern today.”

Women’s 400 meter hurdles winner McLaughlin also mentioned the track after her record-breaking performance.

“A lot of people talked about the shoes, but I do think it’s just one of those tracks,” she said. “It gives you that energy right back and pushes you, propels you forward.”

If the track is working in the way that Mondo says it does, it operates on the same principle as the Nike spikes, according to Burns. “It gives more rebound to the athletes each step,” he said.

A runner takes to the starting blocks during the men's 400m heats at the Tokyo Olympics.

While some people might argue against using technology to speed up race times, others would point out that similar benefits were seen in earlier changes such as the move from cinder tracks to synthetic tracks, said Burns.

“There are always these points in our sports history where we kind of take these steps, and right now is one of them,” said Burns. “Whether or not it’s right or wrong, it certainly divorces us from figures of the past a bit.”

But Burns also admitted that advances in technology might have drawbacks for athletes.

“If you do move performances forward, you don’t know exactly how much of that performance is due to the technology,” said Burns. “When you have an athlete break a record, they no longer get total ownership over breaking that record.”

“It’s that Faustian bargain you make.”

CNN’s Matias Grez and George Ramsay contributed to this report.