This is the link to an excellent presentation that Andrews and Fleisig made to Little League in 2007. It is audio and Power Point slides. Be sure and listen to/watch Andrews presentation. It focuses mainly on overuse, but touches a lot of other topics. Fleisig talks about some to the numbers I posted above, as well as mechanics.
I sure that people will hear what they want to here in these presentations. My understanding is that the studies dealing with curveballs are inconclusive. But why gamble with a kids future?
http://www.littleleague.org/le...itchpresentation.htm