I was fortunate enough to doing some Uechi-Ryu training with a third dan Blackbelt in Ohio. It was some of the most brutal stuff under the sun. It is all about the iron body. We were hit with sticks and things that were supposedly padded. I have to say the worst was kicking the instructor with my shin to the outside of his thigh. After the first kick in knew I was in for bad times. It was like hitting a tree. It got to the point where I was hoping we were done with those but no lets do more. My shin was black and blue and sore for a week! It was really cool though in a sick way I wanted to do it more. Here is a demo video. These guys have the tension thing down to a science.