On October 12, 2019, Eliud Kipchoge did something unfathomable. The Kenyan runner became the first human to propel himself 42.2 kilometres (a marathon) in under two hours. It was a feat that was once considered unachievable. But due to the artificial conditions of the event held in Vienna, his effort didn't count as a world record.

Following Kipchoge's performance, speculation about the shoes he wore Adidas ZX Flux Damen circulated in running communities. Based on Nike patents, it was predicted he wore prototype trainers that included three carbon-fibre plates Nike Air Max 98 Mujer (this ultimately wasn't true) and a high sole height. Pictures from the event showed his prototype shoes also included two airbags under the forefoot.

Last week, World Athletics, the international organisation responsible for running, said it believed shoe technology could be damaging the integrity of running and introduced rules laying out what shoes can be worn by elite athletes in competitions. It added a 40mm limit for sole height for road shoes, said prototypes couldn't be used in officially sanctioned races and decided a shoe can only have one carbon-fibre (or similar) plate inside.

Now Nike is doubling down on its running shoe technology. Ahead of this summer's Olympic Games in Tokyo, Nike Air Vapormax Damen it's unveiled a range of trainers – designed for multiple sports – that use elements of the technology designed for Kipchoge's kicks. They include carbon-fibre plates and airbags – the combination is designed to reduce the amount of energy lost by an athlete's movements.
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The introduction of the products are likely to be followed by a raft of world records and national records falling at the summer games and subsequent athletics events – as long as the shoes are put on sale to the public ahead of time. However, some of the newly announced shoes will be banned under the new World Athletics rules and the company is planning on redesigning some of its products. The reaction is likely to be a sign that Nike wasn't expecting the exact rules put in place by athletics' governing body.

We now know for certain that the Nike Air Zoom Spiridon Femme shoes Kipchoge ran his sub-two marathon in are the Alphafly (full unwieldy name: Nike Air Zoom Alphafly NEXT%). They're a reworked version of the Vaporfly NEXT%, which were released last year and have been used to break multiple world records and lower marathon times of highly performing runners.

The Alphafly are distinctive. They still include a single carbon fibre plate and Nike's soft, yet springy ZoomX foam, that encourages athletes to run on their toes. The trainer's upper is made of a new version of the company's Flyknit material, called Atomknit. It's a thinner and stronger version of the knitting technology.

But turn the shoe over and this is where big changes have been made. Instead of the midsole just consisting of one huge chunk of the ZoomX foam (known in the industry as Pebax), Nike has cut out a chunk of the Nike Air Vapormax Dámské foam towards the front of the foot. In its place are two Air Pods (no relation to Apple). At their simplest, the pods are air-filled sacks placed on the bottom of the shoe. If you think they look like a suspension system that compresses under pressure, that's because it's exactly how it works.