It is both historical and functional. Refuting from a historical perspective any claims that General Choi eliminated "Hip Twist" as an element to generate power with hand techniques, and the functionality or lack thereof if such claim were accurate. Further, in these particular examples there is a slight functional modification due to the designation as "Fast" .
Look at time stamp 16seconds when he says "not that way" and watch his shoulder motion he refers to.
This is my take on it as well. The student didn't seem to be overly twisting his hips, but his left shoulder didn't seem to be squared after the punch. This is generally not good in karate. It also appeared that Gen. Choi was telling the student not to pull his shoulder back (winding up) prior to the punch, which, IMO, is good advice.
Agree. Also, it greatly telegraphs the upcoming punch as vertical motion is easier to detect than a horizontal motion coming straight at you.
If by body you mean the hips, I agree for the most part. Turning the whole body (not keeping the shoulders squared) is counter to most karate doctrine. In contrast, I think some CMA power generation does twist the body when striking.
At :16, Choi brings both his hip and shoulder back saying, "Never twist your body." At :20 and :31, he doesn’t as much and says, “This is fast motion.”
Some southern CMA system (such as WC) also don't twist the body and keep the shoulder squared so both hands can have the same reach. Does karate use that same argument?
Keeping the shoulders square after a punch allows both hands to quickly follow-up and improves body structure integrity to keep the opponent from gaining control of the arm as the shoulders are retracted and anchored. Sanchin kata well illustrates this.
Thanks did he have a concept about using the body to drive power into the punch?
I think the same could be said for how many things are performed in TMA forms. Perhaps that is why forms comprise just one of the 5 elements contained in the composition of Tk-D.
That is correct. He does not say it is this or that. Both are used together. It is easy to see a snippet and misunderstand the intent of a lesson.
Don't know how you define "Drive Power" but this is how I see Sine wave. It is the flexion of the knee or knees which facilitates employing the whole body to drive power. Some boxing boos refer to the use of the legs to generate punching power. There is also the idea of kinetic linking. It is this flexing that results in a smooth rising and lowering f the body that he metaphorically called "Sine wave" so he could contrast it with "Flat Wave" and "Saw Tooth Wave" Not every hand technique in his pattern system uses it. Simple example would be hand techniques done while jumping.
Such as....?
