When I was in my late teens, I had some tryouts with a few Big League teams. I was pitching for a few different teams at the time (school, league, and national team) and really messed my arm up. I thought it was just over use. But it actually turned out to be a form of tendonitis of the bicep tendon. Basically the outter layer of the tendon freys when it is used in a snapping motion (like pitching) and then inflames. I tried to recover from the pain for two years but nothing helped. The Doc said the only solution was sergery but I would have a 20% chance of getting better, 60% chance of staying the same, and a 20% chance of it getting worse due to nerve damage. So I ended up giving up baseball and taking up bodybuilding. The heavy weights don't seem to hurt it at all. Only the snapping motion.
Macdaddy