i can remember reading something about that. and from what i remember, i think its actually possible to build muscle that way. im not really sure though. also like, pushing against your own hands with eachother is also a way to workout, but once again, this is from a while ago. when i was watching this bodybuilding show on FitTV, the body builders said that they flex so hard, that they actually are sore and get a good workout from it. but, not really sure though.