"Bekele admitted on Wednesday that he had injured himself earlier this year trying to use the latest incarnation of Nike's shoe technology.
The shoes, which use a carbon plate and highly resilient foam to maximise the energy returned to runners, have coincided with new world records in both the men's and women's marathon.
"Several times I had some minor injuries, like a muscle stretch, because the shoe is not stable under the foot," said Bekele. "