Other sports have limits they place on the gear - cycling, triathlon, golf. 'This isn't about unreleased prototypes not being available, it's about mechanical advantage. But I don't think athletes should be losing races because they are in a shoe that doesn't have a spring-like mechanism in them. 'I'm all about in technology that help us run faster. 'The only reason I posted was simply to state my opinion that shoes need to be regulated with strict rules so that it's an even playing field for elites across all brands,' he said. He later clarified his statement, saying he was not trying to take away from Kipchoge's amazing performances. 'I'm just hoping makes sure the upcoming Olympics and are fair playing fields for athletes of all brands.' 'It's a spring, and a clear mechanical advantage to anyone not in those shoes. 'With all due respect to as he is clearly the greatest marathoner of all-time regardless of the shoe he is in when a shoe company puts multiple carbon fibre plates in a shoe with a cushion between the plates, it is no longer a shoe,' Hall wrote on Instagram.

Now-retired American runner Ryan Hall, who finished 10th in the marathon at the Beijing Olympics, has called for the athletics world governing body to step in to ensure that runners are not being disadvantaged by not having access to the shoes.

Versions of the Nike shoe were worn by Kipchoge and his team of pacemakers.

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