Now, I think Kevin is probably right in that some wrestlers, fighters, etc are probably using internal structure to a certain extent. And as you noted, some of the fighters are excellent. I certainly wouldn't want to get in the ring with them.
But aiki ... not really.
Funny thing is that as an accomplished wrestler, I can say looking back that the very good wrestlers had certain common characteristics: 1) off-the-charts strength to weight ratio; 2) majority fast-twitch muscles (in comparison to slow-twitch); 3) Incredible stamina; 4) Great body awareness; 5) integrated body movements; 6) NASTY & HUNGRY, TESTOSTERONE-OVERLOADED; 7) AGGRESSIVE WOLVES. Some of the top guys had some rudimentary internal stuff going on, but I would not necessarily say that it was really much to talk about.
The funny thing is that I was trying to work with the local, high school wrestling team. The coach, who outweighed me by 100lbs. could not move me and I could move him around easily (he was an accomplished wrestler as well). He could not really wrap his head around what I was doing and how I wanted to train the team to accomplish it. He dismissed it as not practical! I laughed and told one of the wrestlers (who is a student when not in season) that it is not practical getting more for less
. The problem was that he would have to change some major training components and he was simply satisfied with what he had, rather than achieving the things that I showed him that his wrestlers were capable of doing. Nice, free offer on my part that was not accepted and left me with some more free time for me to work on the fact that I still suck