When Eliud Kipchoge made history by beating the two-hour mark for the marathon, the Kenyan was wearing a pair of controversial Nike running...

When Eliud Kipchoge made history by beating the two-hour mark for the marathon, the Kenyan was wearing a pair of controversial Nike running shoes that has sent rival companies scrambling to play catch-up in a business worth billions of dollars.
The likes of Adidas, Asics, Brooks, Hoka, New Balance and Saucony have recently released or are about to unveil their own carbon-fiber versions of running shoes.
Critics claim the new shoes are the equivalent of mechanical doping, while supporters hail them as a revolutionary technical advance in footwear after decades of stagnation.
Nike said its Vaporfly range, unveiled in 2016, was an “example of how product design can capture the fascination of an entire sporting community and, more broadly, inspire new benchmarks of athletic potential”, boasting an improvement in times by up to four percent.
Elite athletes wearing versions of the Vaporfly, the carbon plates of which lend a propulsive sensation to every stride, have set a rash of personal bests and Nike runners have practically swept the board in long-distance events – they took 31 of the 36 podium places at the six marathon majors last year.
Kipchoge was wearing an AlphaFly prototype boasting three carbon-fiber plates when he dipped under two hours in...