Re: Is power really generated from the center?
Lee, I really appreciate and respect your persistent "how" question. I can't answer very well, but I would like to propose a reason for that: I am not that developed yet, so my meager "center" is not a good reference for defining the final state of that structure.
But I have a hypothesis. Once you have a sense of "intent" and "ki" in the body and strengthen the corresponding tissues a bit, you can use Mark's idea -- by using intent, the center and the periphery have an "accommodational" relationship. When one tries to "accommodate the demands of the center," (or use the center to accommodate a given body shape), the structures in that lower abdomen spot (and hopefully elsewhere) are moving to make that happen.
I would say that there are muscles in that region (including those involved in breathing-- meaning muscles that can apply tension up to the lungs, even thought the lungs are not in the lower abdomen.. hmm, how could that be possible?) which can pull on connective tissue. The accommodation is the preservation of some kind of tautness throughout the body. I hope that last sentence makes sense, because that is the point.