New athletics rules outlaw Nike's record-breaking shoes

World Athletics announced significant changes to its rules on Friday that will outlaw some variants of Nike's Vaporfly running shoes and introduce strict limits to the technology developed for any future shoes used in elite competition.

The governing body's review concluded new technology may provide a performance advantage and could raise concerns that it might threaten the integrity of the sport.

Nike's mass-market Vaporfly Next% model is not among the banned variants.

In a statement, World Athletics said, with immediate effect, road shoes must have soles no thicker than 40 milimetres and not contain more than one rigid, embedded plate.

The Vaporfly shoes used by Eliud Kipchoge to run the first ever sub-two-hour marathon and by fellow Kenyan Brigid Kosgei to smash the women's marathon world record both contained triple carbon plates inside thick, ultra-compressed foam, said by Nike to help improve running economy by up to 4%.

Kipchoge has been the model's flagbearer, also winning the 2016 Olympic title in them, while Kosgei's time in last year's Chicago Marathon took 81 seconds off Briton Paula Radcliffe's 16-year-old record, making her almost three minutes faster than any other woman in history.

Vaporflys have featured in several other records in the last three years and athletes wearing them took 31 of the 36 top-three finishes in the Marathon Majors series last year.

World Athletics' new rules also state that, from April 30, any shoe used in competition must have been generally available to the public for four months -- putting an end to Nike's and others' use of prototypes by its athletes in major races.

There will also be new rules governing the construction of track spikes.

Kipchoge and other leading athletes have welcomed the Vaporflys as a natural technological advance, but others say they have gone too far, with Yannis Pitsiladis, a professor of sport and exercise science at Britain's Brighton University, calling them "technological doping".

Of the rule change, World Athletics president Sebastian Coe said on Friday: "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 Tokyo 2020, while addressing the concerns that have been raised about shoe technology."