<<carefully stepping over Clark's gray matter...>>
I can't add anything to a scientific analysis. However, someone might find the following useful, in regards to thinking of the body as a collection of tubes, particularly the torso (hips on up).
This isn't exactly
what I'm practicing from a visualization
standpoint, but it's the best I can come up with from a "feel" perspective (at least for now). If your torso is a collection of tubes, try imagining incoming or outgoing forces/stresses as a pinball. The tubes can be curved or straight, as long as there are no right angles or kinks. Take the lower-back as an example. If I push open a door, the incoming force may cause my lower back to tighten, creating a kink or corner that the pinball will hit, causing it to ricochet chaotically, on it's way to finding the ground -- if it ever gets there. If instead, I keep a relaxed "hanging" tension all the way around my waist, the ball can ride a nice curve, or plonk straight down through the tube, directly to the ground. If I keep too much tension all the way around my waist or in one spot, the tube will be so constricted that the pinball will simply stop, as it can't get through.
This can still work BTW, if you're using the straight "ground-path" technique from contact point, to middle, to ground. If the ground path is directing the force, then the pinball can represent any undo tension, that is allowed to fall to the ground along with the incoming force.
Or this may have made no sense except in my own mind.