I see so many people playing sports for their entire life and rarely quitting. So I think it must have some sort of addictive properties much like narcotics such as marijuana. So many workaholics seem to pervade these activities that I don't think they are entirely healthy to participate in. With the incredible increased heart rate and injuries such as arthritis, ligament damage, and chronic pain I think we should classify them as illegal. The high people get from exerting themselves is just too likely to be abused.