I found this link<
Thanks to Roosvelt Freeman
Don't know if it's useful to `ya. I thought it was relevant and an interesting description.
Yes. Very interesting.
In Yin ("female") mode it can be used to dissipate and neutralise the force of an incoming opponent by "turning it into an empty place."
When Silk Reeling Skill is used in Yang ("male") mode the spiral movement "collects" muscle force from around the whole body by means of a sort of rising "shock wave" that rides on top of normal body movement. It is first dropped down from the dantian (diaphragm area) to the legs then "bounced" back up the body with additional energy added by untwining the torso as the "wave" rises. Finally this force is "discharged" in the extremities of the body (fist, elbow, shoulder) on contact with an opponent in a frightening pulse of concentrated momentum.
Often both Yin/Yang aspects are combined so that the force of an incoming opponent is "re-vectored." In other words the Silk-Reeling can be used to "rebound" the force of an incoming opponent back upon himself. The faster the attack the faster the rebound - much like objects thrown at a fast spinning top."
Like a spinning top, eh?... what an interesting metaphor
"Shock wave" is a accurate description -- not a metaphor. In aerodynamics, a shock wave occurs at the sound barrier because air at that dynamic pressure passes from an compressible fluid to incompressible fluid. It is a discontinuous boundary
with large threshold energies. Discontinuous changes of sign create shears.
In other words, "Yang" as the poster describes it is a shear in the compressive phase of the wave; "Yin" is a shear in the rarefaction phase of the wave. Since positive and negative they cannot combine at the same point in the same plane without cancelling -- combining them as fully as possible
creates a maximal shear -- a torsional shear
of simultaneous tension and compression, offset by 90 degrees or Juuji
The variations of type, structure, and method of engaging forms of such oscillation with aiki are laid out in a formula ( I'll lay it out reductively; traditionally, its the other way around):-
-- Eight powers (various forms of oscillation)
-- Four souls (the four 90-degree wave phases))
--Three origins or elements (negative, positive and zero relative velocity) and
-- One spirit (Ki -- or speaking mechanically angular momentum
-- which is simply motion defined about one center
involve applying this principle to accentuate and do some nifty trickery
on the spinal reflex systems
of the body.
Or -- it's black arts and magic
-- Clarke's law applies.