Skoorb, agreed. You have to protect yourself from this too though. It's easier said than done, always, but it's something you learn. Keep your head tucked and lock up their arms fast. If you take 'em down face first, which is always preferred, they are even less of a residual threat unless they are some kind of wicked double-jointed or something.
astroview, I was not trying to start an argument either, I've just participated in several of these threads before and they all turn into a "I know this and I can beat your ass!" and "Yeah, well Ken Shamrock is my dad and he can beat up your dad!" blah, blah, blah. I agree, you asked a simple question and got a few objective answers. Mostly though, it's been, this person can beat up that person, etc. BTW, if you want to become extremely physically fit and learn a lot of self-defense and gain strength at the same time, try out wrestling. I don't know how old you are, but your local college may have an intramural program or even hit up your local high school (if you're not still in high school already) and see if they will let you practice with them.