[quote=Franco Cuminato;193280]Well, when I tried to put a joint lock on him, it felt like his whole body, instead of being a collection of bones, muscles, tendons, and ligaments, was one single mass of tissue. STRONG tissue. You and others talk about "fascia", so that must be what it is. While I was trying a kote-gaeshi, he explained (Rob translated) that he was directing my pressure to his center through some lines, although I can't say I actually understand the meaning of "inside lines", "outside lines", etc.[/quotes] Sounds like the "groundpath" idea that Rob and I have talked about before. The path may go to his center, but his center has a direct line to the ground through his leg. So basically, instead of reacting locally to your joint-lock, he let the ground handle your joint-lock.
Regarding his kick, somebody asked me what it felt like, and honestly all I can say is that it felt like being hit by a truck. I don't want to know what his kicks feel like when his back doesn't hurt. Yikes.
Maybe he kicked you with the ground? Of course the body has to be trained to convey/conduct the ground, so you have to do exercises which train the body to do that.