LONDON (Reuters) - Nike said the Alphafly shoe worn by Eliud Kipchoge to break the two-hour marathon barrier would be legal under World Athletics' new rules and that widespread reports of its shoes containing triple carbon plates are false.
On Wednesday Nike Inc launched a new version of the shoe that complies with rules introduced by the governing body last week to limit carbon plate usage and sole thickness for elite races following concerns that technological developments were giving runners an unnatural advantage.
The latest incarnation of the shoe is the Air Zoom Alphafly Next%, with one curved, carbon plate, an insole thickness of 39.5mm, as well added air pockets. The new rules - the WA's first governing running shoe specifications - state road shoes must have insoles no thicker than 40mm and not contain more than one rigid, embedded carbon fibre plate.
"We are pleased the Nike Zoom Vaporfly series and Nike Zoom Alphafly NEXT% remain legal," said the U.S company. "We will continue our dialogue with World Athletics and the industry on new standards."
Nike followed that on Thursday by saying the shoes used by Kipchoge for his unofficial sub-two hour marathon in Vienna last October would still be legal even under the new rules.
"We don't make running shoes with three plates," a Nike spokesperson told Reuters, adding that the midsole thickness was also within the new parameters. Industry speculation that Kipchoge's shoes were triple-plated was based on Nike's 2018 patent for a shoe containing triple plates.
WA President Sebastian Coe, who was a Nike ambassador for 38 years until stepping down in 2015, said last week after most of Nike's Vaporflys were deemed legal that WA "don't believe we can rule out shoes that have been generally available for a considerable period of time".
Another change introduced last week by WA states that, from April 30, any future version, of any shoe, must have been available to the general public for four months before being allowed in elite competition. Limited numbers of the new Alphafly shoes will be made available from this month, thereby ensuring they will be legal for use at this year's Tokyo Olympics.
In the unofficial Vienna marathon, Kipchoge wore a prototype which would seemingly have been at odds with the prevailing rule for World Athletics-sanctioned races that said any shoe should be "reasonably available", though that rule was never applied by the governing body through the various prototype versions of the shoe, which was launched as the Vaporfly in 2016.
The shoe has since contributed to a host of major records and big-race wins and has become hugely popular with recreational runners suddenly slicing minutes off their best times. WA ruled last week that most of the models in the range would remain legal, much to the frustration of many observers who consider the shoes to be "mechanical doping".
Former elite British marathon runner Tam Yamauchi said WA had "given the green light to performance-enhancing shoes", with others predicting they will produce a legal sub-two record, possibly as early as this year's London Marathon in April when Kipchoge, the current holder, goes head to head with Kenenisa Bekele.
After launching the new Alphafly version on Wednesday, Nike Chief Executive John Donahoe denied that the technology gives athletes a mechanical advantage.
"It's simply using the same materials that go into a shoe and putting them together in an innovative way that allows the athlete to do their very best in a safe way," Donahoe said in an interview with CNBC.
(Reporting by Mitch Phillips; Additional reporting by Rohith Nair; Editing by Pravin Char and Christopher Cushing)
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