I think flat feet is heavily associated with pronation of the foot. I have seen photo’s of Mark Lewis-Francis sprinting, and noticed how much he pronates. It’s fairly significant amount. Also since 1998, Ato Boldon has tended to strike the track with a flat foot. Nothing really to suggest the structure of his foot is flat, but his heel was very close to the track when his foot struck the ground. He’s not on his ‘toes’ or the balls of his feet as much as alot of other sprinters out there.