I know it is not worth the time I spend typing this because you old school guys will just keep repeating the same stuff over-and-over. But.....it is not curveballs. Curveballs thrown properly will not hurt anyone. Some coach posted he watched a kid throw 40% curveballs in a game. Thats also not proper. It is also bad baseball. First of all, even a curveball pitcher needs to set-up his breaking pitch with a "fastball" or something.A good curveball pitcher should only throw 15-25% curveballs max. It is time to put away the "push-of-the-rubber"; curveballs are bad stuff. Start reading Tom House, Leo Mazzone, etc. For the last time, arms are hurt by overuse, underuse, overexertion, not warming up and improper follow-through (bad mechanics). "Most arm injuries result not from throwing a particular pitch, but from overexertion, muscling up or trying to throw too hard in a given situation, or overextension." -Leo Mazzone