>> I read an article once that said over 6 hours a week can lead to osteoporosis. It was talking about gymnasts<<
I'm obviously not Cathe.
Anyhow, I don't think osteoporosis is a problem with gymnasts. I had to read a lot of medical journal articles recently on the topic of the effect of gymastic training on growth and health in competitive gymnasts, and I don't recall reading anything about osteoporosis being a problem. They do have lasting problems with injuries and back problems, but not osteoporosis, at least according to the journal articles that I read. Hope that helps.
I'm obviously not Cathe.