MICHEL MARTIN, HOST:
Fans of the Summer Olympics take note - the 2020 games set for Tokyo are just five months away now. And in the runup to the games, the world of track and field has been dealing with a controversy over a high-tech running shoe called the Nike VaporFly. Its design has helped long-distance runners smash records around the world. Kenyan runner Eliud Kipchoge was wearing a prototype when he became the first man to run a marathon in under two hours last year. Critics argue that VaporFlys (ph) cross the line when it comes to performance-enhancing technology in the sport, and they put pressure on the governing body of track and field - World Athletics - to ban them. But in a recent ruling, World Athletics declined to do so. So why is the Nike VaporFly so controversial?
BRYCE DYER: It's turned what is effectively a footrace into an arms race.
MARTIN: That's Bryce Dyer. He is a sports technologist an expert in product design at Bournemouth University in the U.K. He doesn't know the exact science behind this shoe - that's a trade secret held by Nike - but Dyer can talk in general terms about the technology inside VaporFly midsoles.
DYER: It's a polymer, it's a rubber known as Pebax, which is like a trade name for it. And it's that combined with carbon fiber plates that work together to absorb and then return a percentage of the energy that the runner puts into them.
MARTIN: In other words, the shoes literally spring runners forward and help elite runners shave precious seconds off their times. But Dyer says there's another benefit as well.
DYER: Some of the anecdotal feedback that we're getting from runners is that it leaves legs less sore because it's absorbing the energy. It's not hammering the legs - because running is a very, very impact-related sport. So it's not just about allowing the runner to move faster when they're actually racing, but it's also actually allowing them possibly to stitch together more workouts with less fatigue in the longer run as well.
MARTIN: Now, some critics have called the VaporFlys technological doping, arguing that the shoes give athletes an unfair advantage over competitors who are not equipped with the same technology. In fact, Dyer says levelling the field for elite distance runners may be virtually impossible.
DYER: Unless you make all athletes wear exactly the same shoe from the same brand that's scaled to their own body size and abilities, you're never going to be able to isolate or immunize the sport away from the influence of technology.
MARTIN: Last month, World Athletics did issue new rules to more tightly control the use of new shoe designs and competitive events, plus athletes won't be allowed to wear prototypes that haven't been available to the general public for at least four months. But with the Olympics just months away, Dyer says these new regulations may have come too late.
DYER: Athletes who are not sponsored or endorsed by Nike - they may even be sponsored, endorsed by their competitors - now have a problem whereby they're going to be questioning going into these games whether they actually have a technological chance of keeping up.
MARTIN: The medal count and Tokyo may help answer that question. That was Bryce Dyer, a sports technologist and product design expert at Bournemouth University in the U.K. Transcript provided by NPR, Copyright NPR.