i honestly think everything we do in martial arts is somewhat detrimental to our body. the whole cycle of stretching and strenthening, and the process of bone building....we need to stress teh body before it gets stronger. anytime we do this same training regimen for years adn years, we're bound to get wear and tear.. and even tho despite training with perfect techniques, because our bodies are so different from each others, we may still be hurting ourselves in the long run. this applies to all sports and even to everyday occupations (carpal tunnel syndrome anyone?). my comment is not that we cant take precautionary measures, but that for any activity over a prolonged period of time...our bodies are bound to start resisting our beloved activity (shoulder injuries with swimmers, knee injuries with runners, lower back pain wiht labourers, tendonitis with musicians). but of course, even with all the impact MAs gruellingly put us through, benefits outweigh the negatives