NEW YORK, United States — A controversy over Nike's hyper-advanced Vaporfly shoes that some say give runners an unfair advantage could boost sales, especially among amateurs hoping for more spring in their step who would not be affected by any ban.

"Controversy is good for sales," said Matt Powell, senior sports industry adviser at NPD Group. "Nike has not made a lot of pairs here, so [there is] no real financial impact. Amateur runners can still run in these shoes."

The running world is waiting for word from governing body World Athletics, which for months has been examining what to do about the high-tech footwear, used by Kenyan runners Eliud Kipchoge and Brigid Kosgei in stunning performances last year.

Among the options facing the organisation are to impose a wholesale ban on the shoes or take more limited measures to deal with their carbon plate and foam sole technology.

Debate has raged among athletes and commentators about whether the shoes should be allowed and if a ban could be implemented effectively beyond heavily monitored elite racing.

Kipchoge, who wore Vaporflys when he ran the first sub-two-hour marathon in Vienna last October, told the Telegraph on Wednesday that wearing the shoes was "fair" and that the sport should embrace such technological advances.

Nike, the world's largest athletic apparel company, says on its website that the shoe, which retails at around $250, has "a built-in secret weapon." It did not respond to requests for comment on Thursday.

Independent studies have concluded that the shoes, which have a curved, carbon-fiber plate embedded in a layer of lightweight foam, improve metabolic efficiency by 4 percent, though that does not necessarily mean a runner will be 4 percent faster.

"On the surface, banning a shoe for providing exceptional performance wouldn't mar Nike's reputation," said Carol Spieckerman of consultancy Spieckerman Retail. "The controversy could easily increase general sales for the Vaporfly."

Shares in the Oregon-based firm were up 0.5 percent, while rival Under Armour rose 0.6 percent and Skechers USA gained about 1.6 percent. Japan's Asics Corp earlier closed up 2.5 percent.

Nike, which aims to sell $50 billion worth of sportswear this year, capitalised in the 1980s on the controversy around Michael Jordan wearing red and black sneakers that violated the NBA's "predominantly white" rules.

Nike put black censor bars over the sneakers in TV ads and later re-launched its Air Jordan 1 shoes in a "banned" edition. The brand went on to become a billion dollar business.

By Nivedita Balu, Aishwarya Venugopal, Shrivathsa Sridhar, Melissa Fares and Daniel Wallis; editors: Arun Koyyur and Howard Goller.