When a student said to me that Sanchin felt like being crammed into a box I was shocked, it was like getting slapped across the face.(but was a good topic starter

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I see people practicing kata like that all the time, contorting themselves to fit the pattern, I see it with Sanchin I see it with lots of kata, I see it in lots of styles.
It was this kind of conformity and rigidity that coined the term robot ryu in some circles I travelled , it was the exact thing I’d spent so many years getting away from , it’s one of the reasons I was drawn to Sanchin in the first place .
I see Sanchin as liberating , as explorative , as a neutral and mindful pursuit , Sanchin to me taught me all the balance refinement and mechanics to explore movement in general , the battle was never in fitting the kata , but in finding my balance , the simplicity of the kata , versus the complexity of the practitioner .
Experience taught me in Sanchin that deviation from the form was not from a flawed pattern, but from a lack of balance, elbows deviated, knees twisted, balance shifted not from an incorrect mimicry of form, but from an unbalanced emphasis of movement.
The relationship of Sanchin, the relativity, the yin/yang, the balance, the harmonies, however you wish to address it, it was never a question of correcting a movement but finding the compliment to balance the action and remain centred.
If it moves back something must project forward, forward back, over under, up down
As the movement becomes complimentary, it becomes internal, you approach efficiency you generate more from less.
Two lines of force, always joining to one, each move having two expressions, combining to a whole.
To get smaller you add you don’t take away , as the balance of action develops you find yourself in the middle, as you develop your centre the use of the whole body makes the movements smaller easier , and you find the place all movement originates. This often looks like less but is when done correctly the result of more.
Every Sanchin should be different, there is no box to fit in, there is no limitation to how you move IMHO, the only question to my mind is my movement neutral, is every effort balanced, am I complementing my motions.
Kata is the part of martial arts that is introspective, it’s to me the part where you learn yourself, you develop proprioception and kinaesthetic awareness, and you address your pre-conceptions (both mentally and physically) and discover yourself.
You can conform to the pattern, you can force yourself into the box, you can add more effort, more muscle more force, and you can work the external strength, but the route to efficiency on top of attributes (which can be developed many other ways IMHO) is to find your balance, your efficiency.
So one doesn’t IMHO squeeze oneself into Sanchin, but finds oneself out of Sanchin.