An account from Jake McKee on an experience with Koichi Tohei:
The following day we were training sankyo (a wrist twisting technique) and Tohei was unhappy with how we were applying it so he asked me to feel it. “All right, here goes”, I thought. Finally he would apply a move on me!
So I gave him my hand, he twists my palm away from me and in an instant – BAM- I was face down on the mat. Some people talk about ki as if it were a mystical energy or something that feels like electricity going through you. In 20 years of Aikido, I have never felt anything like that.
The perfect aikido (or BJJ for that matter) to me is when you don’t feel any unnecessary muscular tension. Notice I didn’t say “no tension.” There’s always some amount of tension that’s required. When Tohei dropped me to the floor I just shrugged my shoulders and thought, “yep, that’s what I expected it to feel like”.
It was nothingness, it was perfection. The force he used to drop his hands to apply the sankyo was little more than one would use to drop their hands if no one was holding them.
To be clear, Tohei moved to the appropriate position, kept an upright posture, and dropped his hands to apply sankyo. Without tension in his hands or arms, there was nothing to ‘signal’ my body to tense up or try to resist. Relaxed power again.
Aikido For Glasgow 