I like to watch the MTV series "The Challenge." It's kind of a sport. The finals on that show are usually done in teams and it's very competitive and grueling. It takes them days to complete it and they usually throw up and some of the competitors get injured or quit and go home with nothing.
My first thought is rugby because of the heavy impact from the take-downs, but I'm going to go with soccer. A lot of strain on the ligaments, tendons and muscles on the legs and feet.