Nike ZoomX Vaporfly: What are the shoes Eliud Kipchoge wore in 1.59 marathon and why are they controversial?

The Kenyan wore a bespoke version of the Nike Vaporfly trainers – called AlphaFly – a major innovation in the sport which has seen performances sharply improve

Eliud Kipchoge broke down one of sport’s great barriers in October when he ran the marathon in less than two hours. It was a stunning achievement, a feat of humanity that had for a long time seemed if not impossible then many, many decades away.

The effort required a lot of detailed planning, from the perfectly flat course to the favourable weather, and Kipchoge ran behind a well-orchestrated band of pacesetters swapping in and out of position to keep him on track. The fact that it was both pace-set and out-of-competition meant it was not an official world record.

But what has been a little controversial are his shoes: the Kenyan wore a bespoke version of the Nike Vaporfly trainers – called AlphaFly – a major innovation in the sport which has seen performances sharply improve. Here we take a look at exactly what all the fuss is about.

What are Vaporflys and what makes them special?

They are a running shoe made by Nike that is thought to bring significant improvement to performance. Embedded in their thick foamy sole is a curved carbon-fibre plate which Nike research says gives an improved metabolic efficiency of 4 per cent.

How does it work?

The cushioning acts as a propellant, reducing the amount of energy lost as the foot hits the floor and effectively launching the athlete forwards into the next stride.

What’s the difference between the Vaporfly and AlphaFly?

The Vaporfly is the original prototype which one carbon-fibre plate inside a think midsole, and the ZoomX Next% is an advancement of this shoe. The AlphaFly – worn by Kipchoge – is another level, with three carbon-fibre plates and two layers of Zoom Air cushioning pods at the front of the sole.

So are they banned?

Nope, they are legal, and have been used to great effect over the past 18 months or so. Kipchoge broke the marathon world record wearing them while Abraham Kiptum broke the half-marathon world record too.

So what’s the problem?

In many ways there is no problem. Technological advances are a part of sport and always have been, and after all, Kipchoge’s legs are still doing the running. But few innovations have such an instant impact on a sport as the Vaporfly has had on long distance running. Improved performance hasn’t been incremental over decades but near instant, and it has brought into question whether a sporting ethical line has been crossed: is it a form of ‘mecahnical doping’?

Can a shoe really make that much difference?

It seems so. Independent studies agree with Nike’s conclusion that they bring a significant advantage over a competitor wearing ‘normal’ shoes. What’s more, Kipchoge’s shoes were a bespoke design especially for him and his 1.59 challenge, so he may have had even more of an advantage than the original 4 per cent claim. Since the Vaporfly 4% edition, Nike have realised a ZoomX Vaporfly Next% version which is supposed to be even better. Running journalist Nick Harris-Fry recently told The Independent: “I’ve reviewed a lot of shoes and Vaporflys are the only ones that are obviously different – and better – to everything else.”

So why doesn’t every runner wear them?

A lot of runners are now using them, although some cannot for sponsorship reasons. Even then, there was a case of a runner stitching another logo over the Nike swoosh so that he could run in the shoe in competition. For most of us they are still a little elusive though: at elite level they are made to measure, while on the open market they cost more than £200.

So what now?

Rival companies are desperate to match and even surpass Nike’s invention, and Nike are investing heavily to improve what they’ve already got, so this is unlikely to be the end of the story. It is likely to mean faster times, more records and that will bring even more questions. Now World Athletics is preparing to bring in new regulations which prevent the shoes from being worn in the Tokoy 2020 Olympics, and will announce further investigation into the technology and its benefits.