First, my brother is about 6'3", 180, give or take. He is first degree brown belt in Kodokan Judo, and has been in a few scrapes here and there.
Since I have mats and a partner, we've implemented training with each other every Thursday night. I teach him some striking, kicking, and some of the finer points of ground work, he helps me with my throws.
Last night I decided we needed some sparring, albeit light sparring. We started off with one minute, then one minute hands only, then another minute anything goes. Then we went to three minute rounds. It was during this three minute round that he surprised me. We were mixing it up pretty close, and he pulls his hands back, claps real loud, and backfists me in the eye. That one smarted pretty good, and I had no idea what he was doing. A few minutes later, he went to block one of my kicks, but ended up taking it on the kneecap, which damn near ended our training session.
Later, we were doing some combat scenarios, and holding the training knife and defending against the training knife was starting to freak him out a little bit, but that wasn't a big deal. The biggest problem I noticed was that he had no sense of what to target on a person's body for best effect. I got punched in the shoulder a lot last night, to the point where I started making him do a scenario over until he could hit me in a better target.
The last event of the night was some stuff involving knife quickdraws. He reached for it, missed, and so I started grabbing for it. Without even really thinking about it, I did a body ram and planted my shoulder into his short ribs. Whammo! He went down, about a split second later. I'd never practiced this move before, and I didn't put any real force into it. Just a short pull and a shoulder plant. I was very startled at the effect I'd had, I barely felt a thing. He was down on the mat for a couple of minutes, which makes me believe if I'd meant it for real, I could have easily hospitalized a person.
I think that was all that was really notable. I have a fantastic black eye now.
Kent