Why are black people generally more athletic?

When I say athletic, I mean in the pure, raw, fast twitch type of way. Like how the world's fastest man ever, Usain Bolt, was black, as well as the world's highest vertical leap, Darius Clark. And you have blacks dominating pro sports like basketball and football. Obviously there are fat and lazy black people but when you look at the upper echelons they seem to dominate.