PARIS — World Athletics on Friday announced a ban on using prototype shoes in competition after a recent spate of world records set by athletes wearing the Nike Vaporfly trainers.

"From April 30 2020, any shoe must have been available for purchase by any athlete on the open retail market (online or in store) for a period of four months before it can be used in competition," athletics' governing body said in a statement.

The basic Nike Vaporfly has a carbon blade in the sole, which stores and releases energy on each step, and air cushions.

Kenyan marathon world record holder Eliud Kipchoge broke the two-hour mark for the distance in Vienna last October wearing a new Vaporfly prototype with three carbon blades in the sole and four air cushions.

But that would be banned under the new rules which state that shoes cannot contain more than one "rigid embedded plate or blade" of any material, although shoes with spikes can have an additional plate "for the purpose of attaching spikes to the sole".

Kenya's Brigid Kosgei broke Paula Radcliffe's women's marathon world record in Chicago with a time of 2hr 14min 04sec, wearing the basic one-blade version that has been available in shops since 2017.

"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 World Athletics president Sebastian 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."

Kipchoge had defended claims he only managed to break two hours due to his footwear.

"I trained hard," he told British newspaper the Daily Telegraph. "In Formula 1, Pirelli issues the tires to all the cars but Mercedes are the best one. Why? It's the engine. It's the person.

"It's the person who is running, not the shoe. It's the person driving, not the person making the tires." — AFP