Fred Little wrote:
To vastly oversimplify this, what I'm working with is quite simple: the support of the body by means of the soft white underbelly.
Just look at any four legged animal and see which muscle groups and vulnerable areas are protected from external threat as an inherent feature of the animal's anatomy.
Map those muscles onto the roughly corresponding areas of your own body.
Use them to support you when you sit, stand, or move.
The other muscle groups, corresponding to those areas of the animal that are exposed, are all about fine motor control. They CAN be (mis)used for support, and often are, which vastly decreases our ability to generate power (because we're not using the belly/inner surface portions of the musculature and fascia for support) as well as our ability to direct it (because we're using some or most of our fine motor control centers for support).
There are many systems of varying degrees of sophistication to reacquire this and other natural abilities which we have had civilized out of us.
Fred, I've heard that one before. I think it misses the point of yin and yang completely and is sort of a western patchwork gestalt-guess, if you want to use obscure-but-meaningful-sounding ideas. True balance and support would, by yin and yang theory, use a balance of the "yang" musculature (the outer stuff on the limbs and the back) and "yin" muscualture (the inner stuff on the limbs, the belly stuff, etc.).
The idea is that no one would propose to use 'only yang' for anything unless they were an idiot... yet you see westerners using this pseudo-explanation that you just gave, all the time.
"Jin" is a way of explaining a "skill-strength" or a "force vector" and it is the heart of what "kokyu" means. I.e., these were not just "Dumb Ole Chinese" or "Dumb Ole Japanese" that spoke with vagaries and that's how they communicated things... "with feelings that your subtle body can interpret". These guys were masters of descriptions, measurements, etc..... it's a western misconception that they communicated via vagaries.
True, there was a lot of in-house "Masons' Guild" secret-speak, particularly in the martial arts... but I think you're vastly missing what the exactitude of "jin" is and all the related topics. "Ki" actually is an umbrella term... but its relationships all go back to the idea of "pressure" and that's why the kanji is actually accurate and not some sort of metaphor that is open to "feeling".