Overuse is definately the main problem, but let's also mention the lack of knowledge of some coaches on how to develop a pitcher. I'm sure we've all seen/heard of conditioning that is being used for baseball players that actually can hurt them more then help. Who has seen baseball teams using drills really for football players? How about youth league coaches or HS for that matter who do not have their pitchers on a pitching program. They usu pitch then go play another position same day. The next several days they do not have a set program to follow they just wait until they get on the mound again. IMO HS coaches need to get special training to work with pitchers, esp when it comes to conditioning.