Pro athletes will not be able to compete in prototype shoes after April 30, and other regulations impose limits on new shoe technology
World Athletics, the governing body of track and field, announced major changes to its rules on footwear. The new regulations impose an immediate ban on any shoe with a sole thicker than 40 millimeters (mm) or shoes that contains more than one plate.
World Athletics also announced that from April 30 of this year, any shoe used in competition must have been available for purchase on the retail market for a period of four months, effectively banning the use of prototypes in competition.
The new ruling means the Nike Alphafly, a prototype worn by Eliud Kipchoge during his sub-two-hour marathon in Vienna last year, will almost certainly not be allowed among athletes competing for prizes unless it is released with a reduced midsole. The shoe is due for release in the coming months and had recently been distributed by Nike to several of its sponsored athletes.
The previous version of Nike’s Vaporfly series, the Next%, will remain eligible at all levels of competition as the stack height of its heel is approximately 40mm, with a 32mm forefoot stack height and an average of 36mm. While Nike has not announced details of the Alphafly’s composition, industry experts estimate that its heel stack height is above 40mm that it may even contain three plates. (Runner’s World has not received a pair for testing in our labs to confirm.) At the time of publication, Nike had not responded to questions about the stack height or number of plates in the Alphafly.
The regulations are likely to have a drastic impact on the future of shoe technology, which has progressed rapidly in recent years because of the development of shoes containing carbon fiber plates in their midsole and revolutionary new foams.
“It is not our job to regulate the entire sports shoe market, but it is our duty to preserve the integrity of elite competition by ensuring that the shoes worn by elite athletes in competition do not offer any unfair assistance or advantage,” said Sebastian Coe, World Athletics president. “As we enter the Olympic year, we don’t believe we can rule out shoes that have been generally available for a considerable period of time, but we can draw a line by prohibiting the use of shoes that go further than what is currently on the market while we investigate further.”
Is the Vaporfly really that effective?
Yes. Various studies have found the shoe improves running economy by 4-5%, depending on the model, which likely translates to an improvement in race times of between one and two minutes for elite marathoners. A source who tested a prototype of the Alphafly in recent months told Runner’s World it is substantially more efficient than the Next%, with a second source stating it was “unbelievable” and like running “on springs.”
The Vaporfly series has changed the footwear game through a combination of factors: a carbon fiber plate that runs the length of the midsole; Pebax foam (what Nike calls ZoomX) that is extremely light, soft, and ultra-responsive; and a super-thick midsole that effectively lengthens a runner’s leg and allows the plate to work at its optimal angle.
“That ultra-light foam shifted the dial on what’s the optimal amount of foam to put on your foot,” Burns said. “It costs your body less to carry because it’s lighter and returns more energy. Beyond just restoring and returning energy better than other shoes, it’s the same weight as other shoes, but now you have a centimeter and a half longer legs. That gives you a mechanical advantage. ”
If Nike releases the Alphafly to the mass market, runners could face an ethical decision: Will it be as in-demand as previous versions or will runners not want the stigma of setting their personal best in an ineligible shoe?