By: Karen Zhu

In June, Faith Kipyegon from Kenya set new records in the women’s 1,500 meters and 5,000 meters, and Lamecha Girma from Ethiopia achieved a new mark in the men’s 3,000-meter steeplechase, all in the same week. On Friday night, Kipyegon set yet another record, destroying the women’s one-mile world record by almost five seconds when she broke the tape in just 4 minutes and 7.64 seconds. This stunned track fans, as they were used to improvements of mere tenths of seconds.

How?

So, the question is — how? Famous shoe brands like Nike have contributed to these record breakings as they continuously sell “super shoes.” These shoes have been introduced to road running in 2016 and track running in 2019. The first of these shoes was the Nike Vaporfly 4%, and it is said to improve the running economy of professional runners by 4%, hence the name. Several footwear features are behind this performance boost. They include the shoe’s weight, its material composition, the thickness of its heel, and flexibility. The inclusion of a carbon fiber plate, running from heel to toe within the Vaporfly’s foam sole, has been its main and most important innovation. These plates aren’t an entirely new concept, but their specific scoop shape is being credited for the latest performance enhancement. It causes a “teeter-totter” effect, which effectively helps return energy to the runner each time their foot strikes the ground.

Negative or Positive?

A recent pilot study from California State University, East Bay, found some evidence for the “Nietzsche principle”: what doesn’t kill you makes you stronger. They compared runner fitness gains in traditional racing flats compared to super shoes. Those who wore the flats complained of more muscle pain, but they also improved their running economy more than runners who wore super shoes. Two experts in the study of running injuries, Adam Tenforde and Amol Saxena, both believe that super-shoe use can lead to serious injuries. In February, they co-authored an article in the journal Sports Medicine that presented five case studies of navicular bone injuries that stemmed from super-shoe use. “I’ve seen super-shoe injuries in runners at all levels — high school runners, recreational runners, and elite athletes,” Saxena said. “The shoes can put atypical stresses on the bones and soft-tissue structures.”

However, there are no known reviews of super-shoe injury rates that follow standard statistical models. And two leading super-shoe researchers, Wouter Hoogkamer and Max Paquette, say they have not seen any convincing data that runner biomechanics are much different in super shoes than in traditional ones. Both Burns, the physiologist, and Dustin Joubert, an exercise physiologist at Stephen F. Austin State University, have also found that, unlike many people’s assumptions, super shoes have a longer functional life than traditional sneakers. The dense foam midsoles in super shoes, they found, retained their cushioning and energy-return properties longer than the softer EVA midsoles in earlier shoes. The soft cushioning of super shoes could prove a benefit to older runners, too. Bill Salazar, a 77-year-old runner from Arizona, has been training in them for more than three years, logging about 35 miles a week. “The big benefit for me is that I recover faster in super shoes,” he said. He ran a 4:22 marathon in Berlin last September.