[eVILPeeR]

It's really hard on your body, but if you do it in a controlled environment you won't hurt yourself. The worst that has happened to me, was that I fell sideways and landed into the side of a speaker.. no, not the base of it, the mesh part. I have a little mark on my forehead as a result.. and like, a small bruise on my leg from hitting something I don't really remember what.
You just have to be careful about it.. you'll be fine afterwards, but it is unhealthy and hard on your body.