The Science of Running
By Alex Hutchinson Shoe Tech Controversy Continues; Tall Runner, Long Stride; Gut Check
Sifan Hassan hit the jackpot in Monaco this summer, blazing to a new world record of 4:12.56 for the mile (and, as it happens, towing Canada’s Gabriela Debues-Stafford to a national record of her own in 4:17.87). But almost immediately after the dust settled, critics were asking pointed questions about the shoes the Dutch superstar wore: track spikes that looked a little bulkier than the spikes worn by other athletes in the race, even those running for the same sponsor as Hassan, Nike. Was Hassan wearing a new track-friendly version of the Vaporf ly 4%, Nike’s controversial marathon shoe with a thick layer of cushioning and a curved carbon-fibre plate? If so, were the new prototypes race-legal?
For now, we don’t know the answer to that question. Even Hassan’s manager, Jos Hermens, wasn’t sure precisely what shoe she wore to break the record: “Everything is evolving every day, every week,” he told a Dutch newspaper. “To be honest, we cannot keep up with it all…even Sifan.” The swirling rumours highlight a growing controversy about the appropriate role of technology in running. The top-secret introduction of the Vaporf ly at the 2016 Olympics, along with evidence that the shoe provides a speed boost of two to three per cent on average, left many observers uneasy. Yet, others argue that banning shoes simply because they’re too good makes no sense, and ignores the long history of technological progress that enables today’s runners to easily outpace long-ago heroes such as Jesse Owens and Emil Zatopek.
New data about the Vaporf ly, presented in July at the annual Footwear Biomechanics Symposium in Kananskis, Alberta, illustrates this dilemma. Nike researchers shared the results of two internal studies on the shoes. The first explored the role of the curved carbon-fibre plate in allowing runners to cover ground more efficiently. By comparing shoes with various carbon plates, or with none at all, the researchers showed how the Vaporf ly’s plate saves energy by keeping the toes joints stiff without interfering with the ankle’s push-off.
At this point, two years after the shoe’s official release, there’s little doubt that the Vaporf ly does provide a performance boost. But the second Nike presentation offered preliminary evidence for a different benefit: faster recovery. Testing on a group of 14 runners preparing for the Portland Marathon in either the Vaporf ly or the more conventional Zoom Pegasus 34 found that those in the Vaporf ly had lower levels of muscle damage and were able to sustain higher training loads, perhaps because the shoe’s thick cushioning minimized muscle damage.
Although the results of a small internal study like this one should be treated with great caution, the prospect of quicker recovery raises challenging questions about what kinds of technology runners should embrace. If it’s a question of a high-tech, expensive, heavily engineered shoe that makes you a few percentages faster, there’s a strong case for banning it – for saying, “No thanks, we’re happy keeping running as simple as possible, with races whose outcomes are determined by the people running them rather than by the R&D of their sponsors or how much they can afford to pay for shoes.” But if that shoe also allows everyday runners to run more with less soreness, then there’s a more significant opportunity cost to banning them.
The solution to this dilemma remains far from clear. The International Association of Athletics Federations, track and field ’s governing body, has formed a working group of athletes, scientists, and ethicists, along with other experts to study the problem. If they don’t clarify the rules soon, breakthrough performances like Sifan Hassan’s will continue to be greeted with an unwelcome question: what shoe was she wearing?