Good article Chris.
The upward spiral (fire and water -- ka+mi
) and the downward spiral (water and fire -- i+ki
) are -- mechanically speaking -- the spirals of torsional shear lines of (ex)tension (breath of heaven - yo
) and compression (breath of earth - in
), and which lie at right angles to one another) (aiki-ju
) -- forming a complex action that we call "shear stress."
If you consider this post
, and the deeply misunderstood concept of "spherical rotation
" taught by Kisshomaru Doshu, you have a way to understand both unified body mechanics ("unbendable") and loose chain-like body mechanics ("softened joints") -- in one well-studied and consistent mechanical concept that coherently tracks the teaching of O Sensei.
Observe that the combined figure in that post, shown here, has two prominent central crossings, one lower and to the front, and the other higher and to the rear:
These shear lines are the stresses that occur when you twist (rotate
under torsion) a sphere. A sphere is just a minimalist, idealized body. These crossings correlate to the hara (lower front) and the upper cross (upper rear). (The image unfortunately shows them not at right angles because of my limited graphics capabilities -- but you get the point even if it needs to be more geometrically accurate).
The contraction of exhaling rounds the body toward its minimalist shape (topologically, a single sphere in the limit -- and thus, a circular figure). Inhaling expands the body to its more articulated form with outspread limbs ( an X -- in the limit of expansion in all directions) with a major crossing at the hara. This makes the diagonals of the square -- similar to Leonardo's Vitruvian Man.
The control of bodily unity and its natural discontinuities at joints controls the transitions. Winding and unwinding the body is like forming and untwisting balloon animals (i.e. -- the joints can act like the twisted necks of the chains of balloon spheres, free to rotation at the connection -- and they can just as easily unwind back into a single unitary spherical structure where the joints are not free to rotate "bend". The body can thus unify into a monolithic structure -- or fold and collapse again at need by the inverse action -- and all on the exact same principle of action
. Both the unifying and articulating actions are aspects of torsional buckling.
"Softening the joints" = chain-like behavior/iki (articulated for "usage" in the article). "Unbendable" joints = unified body action (the "body"in the article, made unitary).
To complicate matters one can overdrive a twist past the "articulated" body stage and make it spontaneously kink and then "reunify" again in a different way (like overtwisting a chain or a rope into kinked loops that then contract the whole thing -- Try it.) The structure then acts sort of like the chain of free spheres again -- but now is only free to rotate in one
direction, and to collapse int on itself in the other dimension, which it tends to do spontaneously and cannot reverse.
Applied to an opponent, Sankyo
, for instance, is simply a canonical example of buckling uke's articulated structure into a unitary structure by winding him along the fire spiral - upward (extension). Nikyo is the canonical example of winding him into a unitary structure along the water spiral -- downward (compression).