I honestly credit the competitive athletic system in California. You wouldn't think it by the stuff you see on TV, but when I went to school in Cali the athletes were nuts. Not just anyone could make a team, and training centers are usually well funded by rich parents or through the local government with social programs.
Cali is a place where people compete all the time, and kids are heavily encouraged to try any sport. You have places like Ohio that are wrestling hotbeds, and Florida for football, but in Cali everything is a hotbed. To make a point, my sister took gymnastics for a couple years, the make up was 60% female 40% male, find that anywhere else in the US where people aren't training for the olympics.