Date: Saturday, 11 March 2017
Kenyan Olympics marathon champion, Eliud Kipchoge at the finish line of the 2016 Airtel Delhi Half Marathon on Sunday, November 20, 2016. Nike has customized the plates the shoes to suit the three runners attempting the sub-two-hour marathon-Zersenay Tadese, the half-marathon world record holder; Lelisa Desisa, a two-time Boston Marathon victor; and Eliud Kipchoge, gold medalist at the Rio Olympics.
The shoe will weigh around 198 grams, and according to Bignell, the sole is made up of foam never before used in the company's history.
The concerns arise barely a day after the three-man team -Kipchoge, Lelisa Desisa of Ethiopia, and Eritrea's Zersenay Tadese - stepped onto a racetrack in Italy for a real-world test of the Breaking2 team's plans and progress.
The shoes, which are individually tuned to each of the program's runners, work in the opposite direction of traditional running flats by building things up rather than breaking them down.
Nike Zoom Vaporfly Elite was announced on Tuesday, closely following the announcement of the Breaking2 initiative, to have runners run a two-hour marathon.
With an aim to chisel the World Marathon record of 2 hours 2 minutes and 57 seconds to less than two hours, Nike has designed a shoe to do it.
When the Guardian contacted the IAAF to ask whether Nike's carbon-fibre plate was legal, its spokesman Chris Turner said they were interested in its technical advances but wanted to make sure they - and shoes from other manufacturers - conformed to its rules.
While Nike believe the trainers adhere to guidelines, an IAAF spokesman said: 'We are aware of the speculation around the shoe and have received inquiries about new designs of shoes now being worn by elite athletes. "However this is not linked to just one manufacturer".
The Elite is a concept shoe that won't be for sale, but the shoe and its ZoomX tech will be adapted for the mass market as the Zoom Vaporfly 4%.
Former Nike coach Steve Magness has publicly queried whether springs were used in shoes worn by Ethiopian Kenenisa Bekele at the Dubai marathon last month. Given the fact that this run under 3 hours record in 1906 still holds, the sub two-hour race seems achievable.
Three Nike athletes have been training for the attempt, including the double London marathon victor and Olympic champion Kipchoge.