You'll want something that is very strong. Something that can withstand the force of whatever weight you are using in a static situation as well as if you were to drop it (shit happen might as well be safe). It should be just as high as your chest when puffed up/arched back if you have to put the weight down you can exhale and unarch and get out from under the bar.

That would be my take on it.

IronWorker