I'm definitely with KD on the stretching thing. I'm in my 40's and have lifted weights and played soccer, football, baseball, and hockey since I was in grade school. I could probably count the few times I have stretched before participating on one hand. I have always just warmed up with different calisthenics or lifted light weights before starting, and the times I've been injured have always either been from impact injuries or trying to lift too much. I don't recall ever "pulling" any muscles--if I did, it was so minor that I don't recall it.
Oh yeh,I'm also with KD on supervising the ladies swim team's yoga drill also.