In the 1972 U.S. Olympic marathon Trials, a new shoe company called Nike offered many of the marathoners a brand new pair of racing shoes. Over 60 of them ran in the new shoes. Some had issues. I recall the late Ron Daws, 1968 US Olympic team member in marathon reminding his readers that, no matter what the shoe or sock or apparel, never, ever try anything new in a major race.
That is what surprised me on the 2017 Virgin Money London Marathon. All of the brands send out new shoes to their elite athetes. Many brands are testing new products. Elite athletes get access to the product, and try them. Kenenisa Bekele had some issues with his new shoes, which, he believed, affected his performance.
In the heat of battle, which is what a marathon is, things happen. An insole comes loose, a hot spot develops, the foot and legs compensate for such issues, and injuries can develop. That is why so many coaches, trainers suggest that new products not be tested first in major races. Try them out early, take them for your long run before a major race.
I think Kenenisa Bekele has been dealing with some injury issues just before the race. That he finished as well as he did, gutting it out over the last several miles and running back into contention, was pretty impressive. The shoe issue somehow added to the mix, but, elite athletes know, they are testing products that are sometimes good, sometimes not so good. That is the nature of new running products and being sponsored by a footwear company for six figures a year.