I have often written about the posture necessary for power generation and speed in our form of Shorin-Ryu:
- Lower your shoulders.
- Squeeze your lats.
- Tuck your koshi.
- Slightly bend your knees.
- Place your weight at about the center of your feet.
From the koshi side, there is pressure upward from the feet, knees and thighs. From the abs side, there is pressure downward from the shoulders, back and lats. It is like squeezing a big rubber ball sort of (in a very simplified way).
With the body aligned and tensioned in this manner, it is possible to connect the upper and lower parts of the body. This is important, because almost all power comes up from the feet. If there is a disconnect between the upper and lower parts of the body, this power will be wasted or reduced.
So the tucking up of the koshi is met by the pressing down of the abs, creating tension and a useable connection.
It is a very simple thing, but also very important.
Once a student begins to learn how to generate whole body movement using the koshi, I think that it take about two years for the student to restructure or rebuild his body to accommodate and withstand such dynamics. The proper posture won't help much if your muscles and tendons are not properly conditioned.
Charles C. Goodin