quote:...Studies indicate that the curveball is no more stressful on the arm than a fastball...
If and when you can finally get a 12 year old to understand, patiently develop, and then get control of the complex curveball motion, then this is probably correct. The real issue is that the range of 12 y/o's are in such different places developmentally (physically, intellectually, emotionally) that you can't ensure it can be accomplished across enough of them. Some kids don't have the strength to stay on top of the ball no matter how much they know they're supposed to. Then, in a game they start noticing they can still get it to move a little and yet control it better with a slight twisting motion and so they start "cheating". So a lot of kids end up getting hurt, no matter how brilliant and preachy their pitching coaches are about mechanics.
I think everybody gets the overuse argument - its kindof a no-brainer. But its difficult to measure overuse (until you get there) and its a mistake to think that watching overuse will be all you have to do to prevent injuries.