The thing with the unbendable arm is that the relaxed / open hand can be applied to other uses as well. One of the things we do in class is to get a bag holder to close their eyes and guess whether elbow strikes are done with an open hand or a closed hand. Open hand wins hands down, but it’s really hard to wean people off the idea that fist = power. You just get so much more energy in an elbow strike if you keep your hand open. What I did find interesting is that one of my friends who owns his own academy knew the principle but didn’t teach it to any of his students (he never said why) but his wife is a senior instructor and she didn’t know it. LOL, we had a bit of an awkward dinner that evening: “How come I had to learn that from Norm? No ‘dessert’ for you tonight, hubby!”

I think that part of the reason that people think that martial arts is this big mystical thing is because so much of their world view is contrary to what works in practise.