Two principles of Wing Chun that have helped put some of my Jitsu into perspective.
1. The metal rod. (I say metal to differentiate between the rod I'm talking about and the Welsh one
When considering ones balance/posture one should imagine a metal rod through the top of the skull which travels down through ones center and exits a dark shadowy place to the ground beneath. This may not apply to all and every technique however for me it is a very simple way of judging ones posture. Watching students apply arm locks where there shoulders are uneven or their backs are curved, they are looking down at the arm rather than ahead etc are all dead giveaways and I think this is a good way of explaining and questioning posture? A question we should always be asking ourselves and each other..... Is your rod straight?
2. Uke's center
Ideally in Wing Chun when one steps off the line they should change their angle so tori's center always faces uke's center ie whether I step inside or outside my hips etc should be facing my attackers core / centre line / torso. If I block and turn my hips so far as to be facing Uke's attacking arm, yes I can do something with it, however it become harder to effect uke's balance if I only have their arm. To break balance I must effect the Uke's center, this is made easier by ensuring this is always my target so no matter where I step changing ones angle to focus on Uke's center is important. Again this isn't going to apply to everything we do and it's good to play with other angles as well.
Both of these are probably quite obvious but what it is obvious to some is not always obvious to others and it certainly helps me to to teach when I have simple tools to help explain a greater understanding, for myself and students. I also thought it was quite interesting how similar the principles were between Wing Chun and Jiu Jitsu despite the obvious differences. They both promote a direct and efficient use of body mechanics.
There are probably many more principles that apply but I don't know that much Wing Chun
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