'It Stretches the Limits of Performance': The Race to Make the World's Fastest Running Shoe

Natasha Cockram never really cared about shoes. When the Welsh runner entered her first marathon in 2017, she wore a pair of two-year-old Nike racing flats that cost her £15 at an outlet store. And she was a talented athlete: a former junior cross country and middle distance champion, she had won an athletics scholarship to the University of Tulsa in Oklahoma. She studied psychology and raced hard.

“What I’ve always loved about running is that it was so accessible,” Cockram, who is 27, says when we first speak in early September. “All you needed was a pair of trainers. It didn’t matter what they were – anyone could just do it.”

But “just doing it” didn’t seem enough for the brand that built an empire on that phrase. In the year that Cockram began her marathon journey, Nike revealed a radical new shoe during Breaking2, its unsuccessful attempt to smash the two-hour barrier in the men’s marathon with the Kenyan athlete Eliud Kipchoge. The neon Vaporfly shoes, which had thick foam soles embedded with carbon fibre plates, would shake up distance running with their outlandish looks and claim to save a runner 4% in energy expenditure – equivalent to several minutes in a marathon.

The shoes soon inspired accusations of technological doping, not only challenging the purity of a great Olympic event but causing the biggest ethical schism in sports equipment since Speedo’s shark-inspired suits rocked swimming in 2008. The slippery material, versions of which other brands swiftly produced, enabled swimmers, including Michael Phelps, to glide more quickly through the water, triggering a wave of new world records, before being banned by Fina, the sport’s governing body, in 2009.

Runners said Nike’s Vaporflys offered a similar advantage; they felt as if they contained springs, and experts lined up to cry foul. Ross Tucker, a leading South African sport scientist, called them “the shoe that broke running”. Nevertheless, they rapidly sold out, contributing to a near tripling of Nike’s share price and triggering an industry arms race that is still playing out among its rivals. (...)

Only 10 years earlier, distance running had been locked in a very different arms race. As part of a “barefoot” running craze, brands had focused on featherlight shoes with barely-there soles. Nike had looked into minimalist shoes in its early research for what became Breaking2. But runners complained that they were too unforgiving; fatigue trumped any weight advantage.

Nike’s own scientists, led by Matthew Nurse, a biomechanics researcher at the brand’s Oregon HQ, had begun to look for a solution in much thicker foam. But it needed to be lighter. The breakthrough lay in Pebax, a plastic that has been used for years in dozens of applications, including catheter pipes. Produced in raw granules by Arkema, a French company, its chemical structure is a chain of alternating soft and rigid blocks, the ratio of which can be tweaked precisely. Together, the blocks offer toughness and flexibility at a very low weight, as well as a strong energy return, or bounce. “The nature of the chain is not a big secret,” says François Tanguy, a scientist and European manager for Arkema. “How we make it is a very well-kept secret.”

By turning Pebax granules into a foam, Nike got what it needed: a Boost-killer that it would market as ZoomX; an unusually soft, light sole that would return rather than absorb energy, while also reducing fatigue in the brutal last miles of a marathon. A carbon plate – a feature that Reebok and Adidas had experimented with in the 1990s – added structure and support, reducing energy-wasting flex in the toes.

by Simon Usborne, The Guardian |  Read more:

Image: EPA