Athletics records are generally a matter of incremental improvement. It took 18 years, for example, for a succession of six Swedish, British, Australian, and New Zealand runners to whittle the world record for the mile down from 4:01.6 to 3:54.4—a process in which the biggest single gain, 2 seconds, was achieved by Roger Bannister when he became the first to break 4 minutes.
But last week, in Chicago, Kenyan Ruth Chepng’etich cut the women’s marathon record from 2:11:53 to 2:09:56. That’s a 1.48% improvement, comparable to Bannister not just breaking the 4-minute mile, but lowering the record by nearly twice as much as he actually did.
The prior women’s marathon record holder, Ethiopian Tigst Assefa, had lowered it even more dramatically last year in the Berlin Marathon, chopping it down from the prior record of 2:14:04. Combined with Chepng’etich’s new record, that’s like watching the mile record drop by more than 7 seconds in little more than a year.
“People must talk,” Chepng’etich said at a press conference following her Chicago win. And talking they are: the U.S. sports media is awash in speculative claims, disputed by Kenyan authorities, that she must have been doping. Even Amby Burfoot, former editor of Runner’s World, is arguing that the time is too good to be true, especially because Chepng’etich’s prior personal best was nearly five minutes slower.
But there is another answer: super shoes. More specifically, high-tech shoes perfectly tuned for individual performance.
Assefa ran her world record in Adidas super shoes priced at $750 ($US500) and reported to be good for only a single use. Chepng’etich ran in Nike’s latest high-tech model, priced at a mere $450 ($US285).
Super shoes have thick soles (up to 40mm), with hyper-elastic foams and embedded carbon-fibre plates, both of which allow you to rebound more efficiently after impact, with less fatigue as the race progresses. One big indication of their effect is that the Boston Marathon, which limits its field to the 30,000 fastest runners to apply, has been forced to tighten its entry standards by nearly 5 minutes since the shoes first started to appear on the general market in 2017.
A lab study conducted at the University of Colorado, Boulder, found that the earliest model increased running economy—a measure of the amount of aerobic horsepower needed to run at any given pace—by 4%, enough to improve the average marathoner’s time by nearly 3%.
That should have been a red flag that allowing the new shoes in competition was opening a Pandora’s box, says two-time Olympian Kara Goucher, now turned podcaster and NBC sports commentator who spoke to Cosmos.
“If 4% is okay, what about 6 or 8%, or 11%?” she asks. “At some point it’s no longer the same sport.”
The result has been a footwear arms race, as shoe companies compete to produce ever-faster shoes. But there is also an equity concern, not just because the shoes are expensive and wear out quickly.
In 2021, kinesiologists Justin Joubert and Garrett Jones of Stephen F. Austin State University, Texas, had a dozen runners do test runs in seven different super shoes at a pace comparable to a 2:38 marathon. They then measured their oxygen consumption in each shoe, and in a conventional shoe used as a control.
Their main finding was that not all super shoes are created equal—some were definitely better than others. But as a side note, their data showed that not all runners responded the same way. A shoe one runner found to be most efficient might slow another runner down. Some people got very little benefit from any of the shoes, while others saw as much as a 5.9% difference between their best and poorest matches.
A 5.9% difference in efficiency is about a 4% improvement in speed—more than 5 minutes in a 2:10 marathon. Perhaps, Chepng’etich—and Assefa before her—just happened to be the lucky ones whose sponsors’ latest shoes turned out to be perfectly tuned matches.
Doping suspicions are often based on the belief that a performance is too good to be doable without cheating. But that’s a fallacy, Goucher says, because “nobody knows what’s possible anymore.”
Adding to this is the fact that people don’t just race in super shoes, they train in them. “They get less fatigue, run faster, and can put in more hard workouts,” Goucher says. “What happens when they do that for years and years?” she asks.
And that’s just with existing shoe technology. A group at Massachusetts Institute of Technology, Cambridge, Massachusetts, is working on a process that can 3D print critical components of the next generation of super shoes.
Traditionally, says Sarah Fay, now an assistant professor of engineering at Smith College, Massachusetts, the midsoles of running shoes are made of a uniform foam material, with the same properties throughout the sole. But with 3D printing, she says, it’s possible to vary the stiffness of the foam in different parts in the sole, making it softer, perhaps, under the heel, and stiffer under the forefoot in an effort to improve overall performance.
Computer-assisted 3D printing also opens up the ability to create individually customized shoes. “We imagine that if you sent us a video of yourself running, we could 3D print the shoe that’s right for you,” Fay says.
But what about people like some of those in Joubert and Jones’s study who got only small improvements from any of the shoes they tried? Such people aren’t just laboratory curiosities. One is Molly Huddle, who prior to the super-shoe revolution set American records at 5K and 10K. But for whatever reason, super shoes didn’t do much for her. “She identifies as a non-responder,” her friend Soh Rui Yong, Singaporean national record holder in the marathon, recently told The Athletic.
Are people like Huddle just out of luck? And what about all those historical performances from not all that long ago that now look slow. “Are they now suddenly worse runners?” Goucher asks.The reality is that running—a sport generally viewed as low-tech, compared to, say, cycling, skiing, or yachting, is in the middle of a technology-driven revolution with no end in sight. Although the sport must always stay alert to the very real threat of doping, it’s possible—perhaps likely—that within a few years, Chepng’etich’s jaw-dropping performance will become normal, and we’ll be wondering at the next “impossible” performance and debating whether it is too good to be true. Because as Goucher noted, for better or worse, the box has been opened, and things will never be the same.
Rick Lovett has coached competitors in the U.S. Olympic Team Marathon Trials.
The right running shoes
