Most those clips were jacked from AFV. Gymnastic montages were always the best on that show though.
Umm ouch. When I was a cheerleader, one of our girls got dropped out of a simple stunt and had her arm break in a way that looked sooo nasty. I felt bad because all of us didn't even help her, we just screamed and ran away because it was so disgusting to look at. So I can't imagine the injuries some of those girls might have got.
A friend had a spinal injury due to a cheer leading stunt gone wrong. These are not a laughing matter.