The really obvious thing, if you watch the Freeze "best of" clip, is that most people have terrible running form. In most cases, I suspect I could tell who has a chance and who doesn't simply by looking at one stride from each competitor.
There are so many factors that go into biomechanics--I struggle to improve my own running form--but it's interesting to me that it comes together in such an obvious-at-a-glance factor as "looks fast."
In the Freeze video clip from TFA, the guy he's racing looks over his shoulder towards the end too. Its pretty hard to run forward with any velocity when looking backwards. That maneuver alone probably cost him a second, maybe more.
There are so many factors that go into biomechanics--I struggle to improve my own running form--but it's interesting to me that it comes together in such an obvious-at-a-glance factor as "looks fast."