They say shoes maketh the man. But did a pair of trainers make Ethiopia’s Tigist Assefa a record-breaking runner? Her shattering of the women’s marathon world record by more than two minutes – while wearing a pair of Adidas’s new Adizero Adios Pro Evo 1s – has reignited the debate about the role of “super shoes” in athletic performance.
Assefa has credited her performance to “hard work over the past year”. However, speaking before the event, she also described her Adizeros as “the lightest racing shoe I have ever worn”, and said: “The feeling of running in them is an incredible experience – like nothing I’ve felt before.”
Adidas, meanwhile, claims the shoes are “enhanced with unique technology that challenges the boundaries of racing”. So did the shoes or the athlete maketh this astounding performance?
The super shoe wars have been raging since 2016, when all three runners on the men’s 2016 Olympic marathon podium – Eliud Kipchoge, Feyisa Lilesa, and Galen Rupp – were found to have been wearing an unreleased prototype of Nike’s Vaporfly shoes.
Independent scientific tests later backed up Nike’s assertion that the shoes – which contain a carbon fibre plate and a wedge of soft, energy-returning foam – could increase an athlete’s running efficiency by approximately 4% compared with conventional marathon shoes.
Since then, Nike-sponsored athletes have largely dominated marathon running, while subsequent marathon shoes have tended to represent incremental improvements on the Vaporfly design.
Dr Thomas Allen, a sports engineer at Manchester Metropolitan University, said: “There’s been a natural kind of evolution towards lighter foam, greater energy resilience, and a very curved rocker at the front that supposedly improves your biomechanics – particularly around the position of the ankle joint – and helps you to run more efficiently.”
However, in April, the top four places in the men’s Boston marathon race went to athletes wearing Adidas Adizero Adios Pro 3s, and Kenya’s Hellen Obiri won the women’s event wearing a prototype from the Swiss brand On.
Bryce Dyer, an associate professor in product development at Bournemouth University, said: “We’ve gone from a sport where essentially all you needed 20 years ago was a pair of trainers and a vest, to where the footwear has essentially been weaponised quite substantially over the last five or six years.”
Enter the Adizero Adios Pro Evo 1: Adidas claims these shoes are 40% lighter than any previous racing super shoe they have created, and contain a “first-of-its-kind forefoot rocker, placed at 60% of the length of the shoe”, which is “lab-tested to trigger forward momentum and improve running economy”.
Without sawing apart one of these trainers – which has been impossible until now, as they do not go on sale until Tuesday – experts say it is difficult to know whether the technology they contain is truly groundbreaking, or an incremental improvement on what has gone before.
“A lot of the innovations they have in [such shoes] are not obvious to the eye,” Dyer said. “And they’re not something any company is going to publicise for fear of their competitors keeping up with them.”
Even when independent researchers do get their hands on them, dissecting out the contributions of individual components is not straightforward. Allen said: “Unless you can make your own shoes, you can’t just change the rocker, for example, and look at the effect this has.”
Differences in athletes’ body masses, running speeds and foot-strike patterns also influence how much difference individual shoes make. While Nike’s Vaporfly shoes lowered the energetic cost of running by 4% on average, there was considerable variation between individuals.
However, with the potential financial gains so high and the margins of elite sport razor-thin, sports companies have invested heavily in shoe technologies in recent years, making it conceivable that Adidas has hit upon something new.
Dyer said: “Obviously, there is a real incentive [to innovate] when you can still break marathon records by two minutes. There are still a lot of low-hanging fruit on the table that these companies are starting to realise they need to look at.”
Also unclear is the extent to which Adidas has designed its new shoes with Assefa’s physiology in mind. The company claims it has gathered insights from elite athletes, including Assefa and other marathon runners, throughout its development process.
Constructing designs around individual athletes is something Allen predicts will become more common – as Nike did when it set out to break the two-hour barrier for the marathon, which is how the Vaporfly was created.
Allen said: “I think we might see sponsorship deals change a bit, where companies say: ‘We’re going to build you a custom shoe, which you will race in and try to break this record but you’re going to be off the scene for two years while we build it with you.’ And then the company will release that shoe and claim that it is due to the shoe.”
