In March 2017, Nike unveiled a running shoe that it claimed would make people four per cent more efficient. Since then athletes wearing the Vaporfly 4%, or its counterpart designed for elite athletes, made-up 63 per cent of podium finishers in major marathons last year – including Eliud Kipchoge's men's marathon world record of 2:01:39.
Now ahead of the London Marathon on April 28, the company has launched its next iteration of the trainer: the Vaporfly Next%. The trainer, the company says, is designed to make long-distance runners even more efficient.
To do this it has used data to make the sole of the shoe more anatomical, created a new lightweight material, and increased the amount of foam used while keeping the shoe the same weight. Depending on the runner the new shoe could increase their overall efficiency by five per cent, a whole digital more than the company's old shoe. Potentially this means minutes could be shaved from overall marathon times. When you're pushing human limits, marginal gains matter.
"This all round, top to bottom, is a brand new shoe," says Elliot Heath, a product manager for Nike who worked on the trainer. It will be worn by a litany of top runners during the 42km (26.2 mile) race across the capital this weekend, including Kipchoge, plus British athletes including Mo Farah and Charlotte Purdue.
The biggest difference between the Next% shoe and the previous 4% – other than a bright orange colour being dropped for neon green – is its fabric upper. Instead of using the company's Flyknit technology, which fits to the foot in a similar way to a pair of socks, it has created a new thin plastic shell that it's calling Vaporweave. The reason? Runners' sweaty feet.
Nike vice president of running footwear Brett Holts says athletes have complained that the Flyknit material absorbs too much liquid: sweat in hot conditions, water when its rainy. When excess water is sucked into the trainers it adds to their weight, making it harder for athletes running at their top speeds to continue to do so.
The Vaporweave is made of two different plastics. A thermoplastic polyurethane (TPU) thread makes up a mesh while a thermoplastic elastomer (TPE) covers the bulk of the foot. "It doesn't absorb much water at all," Holts says, adding the Vaporweave absorbs seven per cent less than the Flyknit versions of the 4%s. It's incredibly thin.
After the hottest London Marathon on record in 2018, the weather this year is forecast to be rainy. The decision to ditch the Flyknit material for the shoe came from feedback by US marathoner Shalane Flanagan after torrential rain and freezing temperatures hit the 2018 Boston marathon.
Depending on a person's shoe size the Vaporweave is 12-15 grams lighter than the knitted material, Holts says. Despite this drop in weight the Next% trainer is only one gram lighter than its predecessor – coming in at 211g. This is because Nike has added 15 per cent more of its ZoomX foam and tweaked the height difference between the front and back of the shoe. The 4%'s heel was 11mm higher than its forefoot, the difference in the new model is 8mm. Heath says that the increased amount of foam means the shoe can return more energy with every stride.
Nike has purposefully avoided increasing the percentage figure in the name of the shoe – despite saying it can make runners faster. Ever since the 4% was released questions have been raised about whether the carbon fibre plate contained within the middle of the shoe, which acts like a spring to propel people along, provides an unfair advantage. (The plate is still in the Next% shoe).
The rules of running's governing body, the International Association of Athletics Federation (IAAF), say shoes "must not be constructed so as to give athletes any unfair assistance or advantage". In more than two years of use in competitions the IAAF has not banned any Nike trainers that use the carbon fibre plate. A large scale study looking at data from 500,000 races was conducted by The New York Times in 2018 found the 4% shoes did appear to live up to the efficiency claims from Nike.
Ahead of the Next% launch prototype, images of the trainer appeared on Instagram showing it carrying the 5% logo. "That was the inspiration for sure," Holts says. He adds the company decided to go with the non-specific name instead. "It was like, hey, let's keep adding to this but not limit ourselves to five or six per cent someday."
During lab testing of the new shoe Nike has found it improves some runners efficiency by larger amounts. "We're seeing a range of efficiencies," Holts says. "The majority of those are above four per cent, some of them are going above five per cent and some of them are slightly below four per cent".
Turn the running shoe over and it has a peculiar shape. On its sole, the ball of the foot is quite wide and bulbous looking. While there's a large inward curve towards its arch. The unusual structures exist because Nike's algorithms principally designed the shape of the bottom of the shoe based on athlete data.
Starting with elite athletes it collected data based on foot shape and how they hit the ground when landing. After this it then looked at the size and structure of other runners' feet to create a shape that would work for everyone. "We will basically take an algorithm of thousands of foot scans and get that into a foot shape that finds the the median of that," Holts says.
However, you may be waiting a while for the Vaporfly Next%. Nike is releasing a limited run of the trainers on April 25 in London – costing £239.99 – before a wider release this summer.
Looking for some new trainers? Check out our guide to the best running shoes you can buy right now.
This article was originally published by WIRED UK
