I'm curious on why that would happen? I wonder how much of it would have to do with stretching or lack of. I would think it would be a lack of actual game action, in which case there wouldn't be a whole lot that could be done to prevent it. I think a lot of these injuries are also due to bad technique and bad form by the younger players as the games go on. With LB's and S's they get lazy by not squaring up to the LOS and not wrapping up, instead you see guys start diving for legs which can cause some bad things to happen. You also see it with O-lineman who can't move their feet quick enough, and either get tangled up with someone or have someone come down on the backs of their legs. I don't think it has to do with a lack of stretching because to them a game is a game; everyone still goes out onto the field and does their pre-game warmups, goes to get taped up, and approaches it like a regular game.