Well I have said it many times before but Paul McVeigh dramatically changed the BJJ warm ups a while ago and it has made a huge difference in terms of people getting injured.
Commonly we would all get in a circle and one person would say an exercise (such as burpees) and we would all do 10, then the next person would say an exercise (pushups!) then we would do 10. This goes on round the circle.
Good for fitness, but now we all do isometric stretches of the intoerior posterior shatners bosoon or some shit, and injury rates are now very low.