From what I've heard, the age requirement isn't to protect young girls from the rigors of gymnastics -- it has more to do with younger girls having more of a competitive advantage. Gymnastics has always been a sport in which it always benefits you to be younger than your competition...when you're younger, you're more flexible and you're lighter, allowing you to do the maneuvers more easily. When you're talking about young female gymnasts, you also add in the wildcard of puberty -- a 16 year old has to deal with wider hips than a 12 year old, among other things. When you hear the gymnastics experts talk about the subject, they also bring up the idea that when you're 12, you deal with the pressure of the Olympics a lot better, partially because you can't really comprehend how much pressure is there. That's not a theory that I personally buy, but I guess I could see how a 16 or 18 year old would second-guess themselves or would be more self-conscious of their performance.