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The controversial Nike running sneakers that have helped professional athletes all over the world smash marathon records at an astonishing pace, have been approved for international competition, according to an announcement from World Athletics. But while these shoes will be allowed, the international governing body of track and field have added a couple stipulations to its acceptance of technology that's been called "technological doping."

The press release outlines a list of requirements that shoes must comply with moving forward until an indefinite moratorium is lifted:

  • The sole must be no thicker than 40mm.
  • The shoe must not contain more than one rigid embedded plate or blade (of any material) that runs either the full length or only part of the length of the shoe. The plate may be in more than one part but those parts must be located sequentially in one plane (not stacked or in parallel) and must not overlap.
  • For a shoe with spikes, an additional plate (to the plate mentioned above) or other mechanism is permitted, but only for the purpose of attaching the spikes to the sole, and the sole must be no thicker than 30mm.

To enforce this, referees will be allowed to request that a runner provides their shoes for inspection at the end of a race if the official "has a reasonable suspicion" of some foul play. World Athletics has also added a rule that any shoes used in competition must have been available for at least four months for retail purchase starting April 30, 2020. In other words, prototypes will no longer be allowed. Back in 2016, the top three finishers of the men's Olympic marathon all wore a version of the Nike Vaporfly 4% running shoes.

"The new technology incorporated in the soles of road and spiked shoes may provide a performance advantage and there is sufficient evidence to raise concerns that the integrity of the sport might be threatened by the recent developments in shoe technology," the announcement from World Athletics read.

The original Vaporfly 4% running shoe was introduced to the public in 2016 with technology that included a hard foam known as Pebax with a carbon plate that almost literally adds a spring to the step of an athlete who wears them. The Nike product has been proven to give runners a four to five percent improvement on their running economy, the energy utilization measured when a person runs at a competitive (or generally aerobic) speed, which amounts to shaving one to two minutes off an elite runner's marathon time.

The difference is even more impressive among amateur marathon runners, as a New York Times study found. A version of the shoes, known as the Alphafly, was most famously used in 2019 when Eliud Kipchoge broke the two-hour barrier for marathons -- but those sneakers wouldn't be allowed now, as they contain three carbon plates and have a sole thicker than 40mm.

World Athletics president Sebastian Coe said that while he's not in the business to regular the shoe market, it is his duty "to preserve the integrity of elite competition" by making sure certain athletes don't have shoes that give them any "unfair assistance."

From Coe:

"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. I believe these new rules strike the right balance by offering certainty to athletes and manufacturers as they prepare for the Tokyo 2020 Olympic Games, while addressing the concerns that have been raised about shoe technology."

He added that World Athletics won't hesitate to "tighten" the rules if move evidence indicates they need to.