New on Sports Illustrated: Nike VaporFly Shoes Avoid Ban as World Athletics Imposes New Limits on Shoe Technology

World Athletics issued new regulations on new technology amid controversy regarding Nike's VaporFly shoes.

On Friday, World Athletics, the global governing body of track and field, released new regulations on footwear, banning any shoe with a maximum sole thickness of more than 40mm and shoes that contain more than one plate.

Under the new regulations, the current version of Nike's VaporFly Next% shoes—which have been popularized by elite and amateur runners, but have stirred debate regarding their threat to the integrity of the sport—will not be banned. The Nike VaporFly Next% shoes have a stack height of 40mm, which would meet the limit.

The future of shoe technology will likely be impacted by the governing body's new ruling, which improved upon its previous, vague stance, which read: “Shoes must not be constructed so as to give athletes any unfair assistance or advantage.” A technical committee was established in November 2019 to examine controversial footwear in hopes of a resolution to the growing uproar and concern before this summer’s Olympics. Nike has repeatedly said its shoes meet the IAAF requirements and do not violate any rules.

Under the new rules, any shoe must be “reasonably available to all in the spirit of the universality of athletics,” and, to impose that rule, any shoe that is introduced to the open retail market after April 30, 2020, may not be used in races unless it has been available for purchase by anyone for at least four months prior to competition. If a shoe does not meet these criteria, it is considered a prototype.

The new rules also state that shoes must not contain more than one carbon fiber blade, plate or “any other material with similar properties or producing similar effects, whether that plate runs the full length of the shoe or only part of the length of the shoe.”

In the

release, there is an additional note from World Athletics:

“At least four months prior to an International Competition at which an athlete proposes to wear a shoe that has not previously been used in International Competitions, the athlete (or their representative) must submit to World Athletics the specification (i.e. size, dimensions, sole thickness, structure etc.) of that new shoe; confirm if the new shoe is to be customized in any way; and provide information about the availability of the new shoe on the open retail market. After reviewing this information World Athletics may request that samples of the shoe be submitted by the manufacturer for further examination. If the shoe is requested for further investigation, World Athletics will use reasonable efforts to complete its examination as soon as practicable (if possible, within 30 days of receipt of the shoe by World Athletics).”

World Athletics also stated that if it believes a shoe or specific technology does not comply with the letter or spirit of the rules, it can call for that shoe or technology to be prohibited in competition until fully examined.

Nike’s VaporFly shoes, which are easily recognizable in races due to bright-green and pink colorways, have been at the center of controversy dating back to 2016, when several sponsored athletes competed in prototypes at the U.S. Olympic marathon trials and then at the Olympics in Rio de Janeiro. Critics say the shoes, which feature a carbon fiber plate and cushioning foam in the midsole, provide an unfair advantage due to the energy return that has led to faster times than competitor shoes. The shoes have resulted in an arms race among other companies such as Saucony, Asics, Brooks, New Balance and HOKA One One to create a competitor that can keep up, with target dates as soon as the U.S. Olympic marathon trials on Feb. 29 in Atlanta. Saucony, Brooks and HOKA also now have shoes that feature a carbon fiber plate.

Those companies may now have to rush their products out to be eligible for use at the Summer Games in Tokyo.

In July 2018, The New York Times released the findings of its own study using data from fitness app Strava that determined runners in the Vaporflys clocked times that were 3% to 4% faster than similar runners in other shoes. It also found that the Vaporflys were more than 1% faster than the next-best racing shoe. The Times analyzed results from about 280,000 marathon and 215,000 half marathon performances. Last December, the Times revisited the latest shoe technology to include the Next% and found that runners were 4% to 5% faster than the next-best shoe.

Nike officially unveiled its VaporFly technology in 2017, when the sportswear company sponsored an optimized exhibition race for Kenyan marathoner Eliud Kipchoge to break two hours in the marathon. Kipchoge fell just 25 seconds shy of making history but in addition to the perfect course, fueling and weather conditions, the shoes made a marginal difference. He wore the 4% shoes when he broke the marathon world record in two hours, one minute and 39 seconds at the 2018 Berlin Marathon. Three years later, the sportswear company upgraded the shoes for Kipchoge to wear at the 2019 London Marathon with its VaporFly Next% shoes, which have more foam than the 4% and are composed of lighter upper material. He ran the then-second-fastest marathon time in history with them and won the race in 2:02:37. The five-fastest marathons in history have been run by men in VaporFly Next% shoes.

Fellow Kenyan Brigid Kosgei amplified the VaporFly debate when she broke Paula Radcliffe’s marathon world record of 2:15:25, which had stood since 2003, by 81 seconds. Her 2:14:04 world record at the Chicago Marathon came just one day after Kipchoge became the first man to break the two-hour marathon barrier and gave the world a sneak peek at the next installation of the VaporFly tech.

During the INEOS 1:59 Challenge, another optimized sub-two attempt, Kipchoge wore the AlphaFlys. Nike released photos of the shoe, but very few details. A patent was uncovered by a running blog that suggested the new shoe has four cushioning pods on the sole, two layers of midsole foam and three carbon fiber plate layers.

The shoe has been seen in some domestic U.S. races as a prototype on wear-testers and also on some U.S. contenders for the marathon trials like Bernard Lagat—who will be going for his fifth Olympic team at 45. Under the new regulations, the Nike AlphaFlys will not be allowed at the U.S. Olympic Trials, since they are still not on sale to the general public and, thus, do not meet the availability guidelines set by World Atheltics.  

The new regulations set by World Athletics are a step forward in limiting the manufacturer arms race that’s distracting from the athletic footrace, but shoes are more complex than putting a blanket limit on the construction. Now that there are defined limits, it seems that the the next step for footwear innovation will be working within World Athletics’ constraints to optimize shoes for individual runners.