Well, someone just p.m.'ed me that it is "energy" that is spiralling. In the technical sense, it cannot be actual energy (where does it originate from, where does it get power from, how does it work that you can control "energy", etc.).
In one sense I agree, there is no mystery "energy" involved. Yet in another sense, I do not agree. Stress is a potential of mechanical energy, stored in the material of the structure itself and directly transmitted by it.
Shear stress, with or without torsion, is a simultaneous composite potential of both compressive and tensile mechanical forces that do not cancel each other out -- which is hard for most people to envision -- much less to sense in a discriminating manner so as to manipulate them separately. Hence we get various diagrams and much verbiage and various approaches to training attempting to understand them.
The first indisputable observation is that shear stresses in a cylindrical structure in torsion form complementary spirals of coherent but opposite stresses - both tensile and compressive. When you load the cylinder in torsion, it retracts on its long axis; and when you unload it from this stressed profile, it extends.
Your body is a set of connected cylinders, made up of bones, muscles and fascia, from core to surface. The fascia are the outermost structural fiber of the limb and therefore have the highest effective structural shear load, which is at the surface of the cylinder. If you engage them, they can do more to resist (and store) torsional shear energy than muscles or bones can do. Indeed you can use your bones and muscles to create these loads isometrically, and release them to strike or actuate the body in other ways. Tegatana
are the traditional terms that describe the two inverse torsional stress profiles in the arms, for instance.
The second indisputable observation is that shear stresses can be transmitted by waves of purely local motion, which receive and invert these stresses sequentially. A wave in water or air alternately compresses (peak) and then stretches (trough). Spirals and waves are mathematically equivalent, and waves can take form in a plane, or a surface, in a bulk mass (as with sound waves), or in spirals of torsion.
A chain of links transmits such mechanical energy in the same fashion. The limbs are chains of bones. A linked chain cannot be passively compressed, yet one can strike quite devastatingly using a unfurling chain as with a punch to deliver the "ground path" without any compressive forces developing in the chain at all. Properly done, the ball or dart is not merely 'thrown' with a fixed momentum but actually accelerates
in its travel toward the target after release, as any true whip does. How does your 'ground path' approach explain the chain whip or meteor ball straight strike? The only "ground path" is in explicit tension
The second observation combined with the first applies to the "no inch punch" -- just starting from the poised static stress profile instead of the completely dynamic one, as with the chain whip. This is perfectly sound physics, and my approach makes this both comprehensible and more generally applicable. The first and the second observation involve slightly different aspects of angular momentum in motion and stored moments/shear/torsion in potential.