Robert John wrote:
I'll interject here, while Japanese doesn't have an exact term for Jin, they do often use the term "hiriki" or "elbow power" (referring to the specialilzed type of power you use when you train the body using the bow, or other weapon).
And from my experience, it's basically yes, a willfull coordination of deep muscle tendon (rather than muscle itself).
The Qi/Ki paradigm that Mike refers to (correct me if I'm wrong here Mike) is connecting that Jin/hiriki with the power developed by specific breath related exercises. (thanks by the way for the hen/ha type hint that you gave earlier, realized some more stuff today
The breath related exercises develop a type of power/skill that is used in conjunction with your already developed Jin/Hiriki skill.
I'll also bet, unless you already have structure/Jin/Hiriki skill, 10-1, doing the breath exercises won't be nearly as useful, and any skill gained from it will be kind of dicey...
It's why even the old JMA peeps used to train simple weapons until their legs gave out. They had to first develop a solid structure/hiriki before you could even begin to seriously start to develop the breath power which combined was referred to as "ki/qi".
As usual, it's obvious to me that we're talking about the same things, even though we have different backgrounds and different perspectives on some things. I agree with everything you've said, more or less, EXCEPT I'd throw out a caution about the "deep muscle tendon" concept. You're getting into a tricky area that demarcates "Shaolin" (Buddhist) from the supposed "Taoist" training methods, in some of the juvenile conversations (in reality, there is so much overlap, it is impossible to separate the two). While the fascia network permeates the body more like a sponge than anything else, the initial approaches to it are normally via the superficial myofascial structures, not the "deep muscle tendons". In other words, you're getting a bit to close to brute strength (even though you're doing it in a tendon-related manner) than I'm comfortable with (i.e., I need to indicate that I want to hear what you say without either agreement or disagreement).
Let me try to illustrate my area of concern. If someone is standing in a "tree hugging" posture and they pretend that they're actually standing in a hole dug in the ground so that their feet are on the ground in the hole and their elbows are resting on the grass around the top of the hole. Next they mentally try to rest their body-weight on the elbows and undersides of the arms somewhat. To add to that resting of the weight, they slightly attempt to raise both knees at the same time. This visualization sets up a standard "contradiction" within the body, although to an outside observer, nothing may appear to be happening.
The trick is in the level of contradiction that you're training. If you back off until the contradiction is just barely felt, you can actually be muscularly more or less relaxed, yet the contradiction is still felt throughout the body. This is the level I would suggest is appropriate to train the ki/qi as opposed to anything approaching "deep muscle tendon", because there is another important level beyond this that can't be entered if there is too much tendon/muscle involvement. The tendons will develop over time; the danger of going off on a tangent can be heightened by trying to rush too quickly into higher tension usages, IMO and FWIW.