Nike designers explain how they created a shoe that helped Kenyan runner Eluid Kipchoge come within seconds of breaking the two-hour marathon barrier in this exclusive movie produced by Dezeen.
Nike's designers and scientists worked with athletes to develop the Zoom VaporFly Elite shoes specifically for the Nike Breaking2 project. The event staged in Monza, Italy, on 6 May saw runners attempt to complete a marathon in under two hours.
Kipchoge fell just short of the mark wearing the trainers. But his finishing time of two hours and 25Â seconds was almost three minutes faster than the official world record of 2:02:57, set by Dennis Kimetto in Berlin in 2014.
"Eliud Kipchoge ran the marathon in two hours and 25 seconds, knocking almost three minutes off the previous world record time, which is absolutely phenomenal," says Tony Bignall, vice president of footwear at Nike.
"Now we'll go back to the drawing board and learn what comes next," he added.
Contrary to recent trends towards sock-like trainers that emulate the experience of running barefoot, the Zoom VaporFly Elite features a high level of cushioning in the sole to protect the athletes from the impact of running on concrete.
The lightweight foam used in the sole enabled the designers to incorporate a hefty 21-millimetre stacked heel without adding too much weight.
The shoe also features a custom-engineered carbon-fibre plate embedded within the sole, propelling athletes forward and stiffening the foot to prevent fatigue.
"There's three of these shoes in existence for each one of the athletes and each of those shoes is different, because it's customised for them independently," explains Stefan Guest, senior design director at Nike.
Kipchoge ran alongside half-marathon world-record holder Zersenay Tadese of Eritrea and two-time Boston Marathon champion Lelisa Desisa of Ethiopia, but was the only athlete to complete the 26.2 mile distance.
The early-morning attempt took place at the Autodromo Nazionale Monza near Milan, which hosts the Formula One Italian Grand Prix each year.
The athletes ran around a 2.5-kilometre loop of the racetrack, which was chosen to host the event because of Northern Italy's low winds and mild temperatures.
Despite shaving almost three minutes off the world record, Kipchoge's time will not be official as the runners benefitted from pacemakers and moped-delivered sports drinks – these wouldn't be permitted under ordinary marathon conditions.
"People are taking seconds off every time the record breaks," says Brad Wilkins, a director at the Nike Sport Research Lab.
"If they can't do it, no matter what piece of footwear I put on your foot, it's not going to make you do it," he continues. "But, there's definitely a synergy with getting the right footwear onto the right athlete, and we've seen that the footwear can definitely help an already great athlete be even better."
The Zoom VaporFly Elite was designed solely for the Breaking2 attempt and will not be made available to the public. However, consumer versions of the shoe – the Nike Zoom Vaporfly 4%, Nike Zoom Fly and Nike Air Zoom Pegasus 34 – will be released on 8 June.
Each features an upper constructed of Nike's signature Flyknit textile and more conventional variations of the Zoom VaporFly Elite's design.