- When your elbows (and/or your knees) are moving away from each other (away from the body center) you are expanding.
When your elbows (and/or your knees) are moving closer to each other (closer to the body center) you are contracting.
Everyone seems to understand expansion instinctively. Oi-zuki... step forward into a long front stance and extend the arm in a punch. Expansion!
It takes a special effort to comprehend contraction, which occurs during the first half of the step forward, while the rear foot is catching up to the supporting foot. This is not a casual motion but a hard, fast muscular contraction involving the groin muscles (sartorius), that transitions to expansion as the second half of the step.
When students finally connect with this, they stop bobbing up when stepping. The contraction is the first stage of the launch forward. As the moving foot passes the stationary foot, we transition from contraction to expansion. Expansion is the second stage, and it builds on the first. Contraction launches; expansion accelerates.
The student needs to get in touch with the sartorius muscle... one he has never consciously used in his life... before he can attempt contraction. One way to do this is to put him in zenkutsu dachi... right leg back... and teach hiza geri as in Heian Yondan step 24. Repetition of this move with speed and focus is a natural way to introduce the powerful forward contraction of the rear thigh/knee that brings power to the strike. When the muscle is aching a bit you can point out where it is, and how important it is to the basic principle of contraction.
To teach the principles of expansion and contraction I also like to work the third move of Heian Shodan... technically steps 3, 4, and 5.
A powerful contraction stepping backward at the beginning of move 3 sets up the momentum for the clockwise spin. The contraction also brings in the knees and elbows to accelerate the spin... think of an ice skater spinning. The momentum of the body naturally flows into the subsequent expansion, and some of the spin can be bled off into the gedan barai. The simple first step... withdraw the front foot backward hard and fast, using the momentum to spin... gives students a way to experiment with contraction and see the results for themselves.
Once past step 3, there is clear application of contraction in step 4 as we contract powerfully back, away from the block, to effect the wrist release. Students can feel how the contraction powers the technique... not just the arm muscles.
The circular setup for the tettsui emphasizes how contraction must flow into expansion. Technically the tettsui strike is another example of contraction... this time contraction of upper body while lower body is expanding... which we can leave for a more advanced lesson.
Once steps 3 and 4 are well advanced, present step 5. This is a oi-zuki in zenkutsu dachi. Let the students do the technique without prompting, and watch how most of them miss the contraction phase at the beginning of the step. Ask them what they missed. Point out that the same powerful contraction that fueled the previous two moves is essential to the first half of every step in the kata. Then work the whole H. Shokan kata, emphasizing contraction... contraction... contraction... on every step, and watch how exhausted they are at the end of it. Until this lesson is learned, most students perform only the expansion half of each move. They're doing only half the kata!
