The record-breaking Nike shoes worn by Eliud Kipchoge in 2019 are among the modern shoes being scrutinized in terms of legality in professional competition.
World Athletics, running's governing body, is looking at the legality in professional competition of modern shoes, including the Nike shoes worn by Eliud Kipchoge when he became the first person to run a sub two-hour marathon last year.
Kipchoge wore a protype Vaporfly from Nike, called the Alphafly, when he set a sub two-hour marathon record in 2019, which wasn't ratified by World Athletics because it was not set in a proper race.
Kenya's Brigid Kosgei also wore Nike's Vaporfly Next% when she beat Paula Radcliffe's 16-year-old women's marathon world record last year. The shoes, as well as similar designs from other brands, are being scrutinized by a panel of experts convened by World Athletics.
While the Nike shoes are considered legal, a 2017 study published in the journal Sports Medicine suggested Nike's original Vaporfly 4% offered a boost in running economy of around 4% compared with another Nike model and a top trainer from Adidas.
Running economy refers to the measure of the amount of work a runner must do at a given speed. A 2018 New York Times study confirmed the results and pointed out that the top five fastest men's marathon times in history have been set by runners wearing Vaporflys.
World Athletics' rules say shoes "must not be constructed so as to give athletes any unfair assistance or advantage." Rule five adds: "Any type of shoe used must be reasonably available to all in the spirit of the universality of athletics."
In a recent statement, World Athletics said a working group, including officials, athletes, scientists and lawyers are reviewing shoe technology and the wording of the rules. A spokesman said that a decision is likely by the end of this month.
