
I was reading something about him a couple of days ago mainly about how he does it. Apparently he goes against the percieved wisdom in theory taller runners should be fast because there stride length is greater but normally shorter runners have faster leg speed they make up for it, so there is an 'optimum' size that means a good stride length with fast leg speed. Usain Bolt goes against this in that he has a long stride (over a hundred meters he takes 3 or 4 fewer strides than his rivals) but he has similar leg speed to his rivals hence he is so much quicker.
Apparently there are some people who are worried he may set a world record that will never be beaten simply because he is so unusual.