The science of simple machines doesn't always apply to human beings, I mean, come on - A thin, wiry guy who has relatively little muscle mass who is shorter than me and lighter than me shouldn't over power me. But what if he does? Perhaps he's a psycho or just lean and mean or has amazing ki power. Now how is science going to screen out what works on him and what doesn't? What about the guy who can't feel pressure points because he's just that tough? Or the one who is so damn flexible that you could almost fold his hand against his arm and feels no discomfort until the bones actually break or the tendon or ligament gives? Science just won't always screen everything out. I stand by what I said - a rudimentary understanding of physical science and body mechanics is helpful. But I agree with one thing RMcRobertson said - practicing proper technique application should be first and foremost. The ability to "feel out" your opponent should supercede everything.