...example to show a principle: if you are going to expend the energy to...
If it's a unifying principle for efficient movement of the whole body, then it should carry down to any joint(s) you look at. I think any small example should embody the entire principle, rather than just something kinda sorta maybe like it. In this case it was the joints of the wrist and arm, but could just as well be the toes, the fingers, the rotator cuff of the shoulder, the hip joint, the knee joint, the ankle joint, the neck, and onward ad nauseum.
Or to quote Neuromechanics of Human Movement - Third Edition, Roger M. Enoka, p102
Because the human body does not behave as a single rigid body, such as the bat, it is necessary to consider the motion of each body segment when calculating angular momentum. This requires a linked-system analysis, in which we calculate the angular momentum of each segment about its CM [center of mass] (local angular momentum) and then determine the angular momentum of the CM for each segment about the system (whole body) CM (remote angular momentum).
Thanks Lee. Very much in line with what I have been trying to piece together. I will have to get me a copy. It may help in better describing how the process of aiki both disrupts and optimizes those mechanics.
For another off-the-cuff example of an exercise of similar character , get two used milk jugs (full of water) or a hand weight of 10-15 pounds or so.
First. Curl the weight with the bicep to the shoulder rest position (this is what it should NOT feel like) .
Second. Swing both weights from side to side using hips and torso only, with no muscular flexion, with the arms wrapping the torso slightly at the reversals ( this is what it should feel like when you raise them, shortly).
Third. Raise one weight to the shoulder rest position using the hip to throw the weight there, using the hips only, and no muscular flexion at all.
Fourth. Alternate doing it left and right in this manner, in continuous sucession.
Fifth, Raise both together the same way. (funetori).
Sixth. Perform happo undo with the weights, reorienting them as in the second exercise, and raising them together the same way each time in each new direction
Seventh. Substitute a person(s) for the weights and do the same things.
Eighth. Have fun