Nike launches retail version of Eliud Kipchoge shoe it says complies with rules

Nike has launched a mass market version of its controversial Alphafly prototype shoe that it says complies with new World Athletics rules.

On Friday, the sport's governing body introduced an indefinite ban on any shoes that have a sole thicker than 40mm or more than one rigid embedded plate or blade.

The prototype shoes worn by Eliud Kipchoge when the Kenyan became the first athlete to run a marathon in under two hours in October do not meet these restrictions.

But Nike said the retail version of the Zoom Alphafly Next%, set to go on sale this summer, will do.

"We are pleased the Nike Zoom Vaporfly series and Nike Zoom Alphafly Next% remain legal," said Nike in a statement.

"We will continue our dialogue with World Athletics and the industry on new standards."

Any new shoe technology developed after 30 April will now have to be available on the open market for four months before an athlete can use it in competition.

In bringing in the new regulations, World Athletics did not ban the Vaporfly range, the predecessor to the Alphafly.

It is claimed Vaporflys improve an athlete's performance by 4%. The five fastest marathons of all time have been run in the past 16 months by athletes wearing varying forms of the technology.

On Wednesday, Nike also launched a new Viperfly sprint shoe designed for the 100m that does not meet World Athletics' new restrictions.

For shoes with spikes, an additional plate or blade is allowed for the purpose of attaching the spikes, but the sole must be no thicker than 30mm.

Nike said it will now be working on the Viperfly accordingly.

Analysis

BBC sports editor Dan Roan

Given the controversy sparked by the way Nike's earlier Vaporfly shoes turned distance running upside down, the release of the Alphafly is sure to reinforce mounting fears that they could distort distance running and mean unfair competition at the Tokyo Olympics.

The fact the foam sole thickness of these shoes comes just fractionally inside the new 40mm limit announced by World Athletics last week will also lead to concern that the rules were too accommodating to Nike, and too generous. It will be interesting to see how other shoe manufacturers respond, and whether the number of patents Nike have taken out hamper their attempts to do so.

The new bizarre-looking Viperfly spike shoe is said to currently exceed the new regulations. But with Nike vowing to modify it accordingly over the coming weeks, could the sprinting events in Tokyo also be overshadowed by claims of 'technological doping' and a wave of new records? All this intrigue may be invaluable publicity for the company. But it is also gives athletics plenty to ponder.