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Old 08-14-2008, 04:03 PM   #107
Erick Mead
 
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Dojo: Big Green Drum (W. Florida Aikikai)
Location: West Florida
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Re: "Aiki" in Russian Video Clips

Quote:
Dan Harden wrote: View Post
Well I did make a mistake in stating "Erick was waste of time." Sorry Erick.
What I meant to say was "For purposes of this discussion Ericks attempts to detail and model what we are doing without any experience is a waste of time for those trying to learn or understand."
Well, let's see about that.
Quote:
Dan Harden wrote: View Post
For that matter...as I outlined... I think my own descriptions are a waste of time.
Don't be so hard on yourself.

Quote:
Dan Harden wrote: View Post
When doing Shiko "Open your pelvis, put your intent from your left foot to your right hand. Cross-line body work is very important. pull yourself back upright with your left leg pulling your right side hand back up, while your left hand draws your right leg up and you right leg is pulling down. Maintain and hold these six contradicting lines in your body; up/ down, left / right, front/ back, and while you are doing that hold a connection from your feet to each opposite hand. If you can; try rising up in the back and sinking through the front, at the same time. Do it till your intent is so refined that "your will" pops you off your own feet when you go back upright. Oops I see your spine let your sort of slide over and your postural alignment broke!"
There are two key mechanical points in the exercise:
"Draw yourself over with your right hand, "pull yourself back upright with your left leg pulling your right side hand back up",

"... left hand draws your right leg up and you right leg is pulling down."

Since after you draw yourself over you are supporting weight on one leg, the spiral formed through the torso to the opposite arm is in compression.

The unloaded spiral of the matching opposed arm/leg is not limp, but "pulling, " i.e. --in tension

Look at the torsion tube stress diagram again and see the stress lines in 90 degree offset tension and compression on the bias with respect to the long axis -- matching the opposed tension compression in the limbs in shiko at the elevated position .
http://www.aikiweb.com/forums/attach...9&d=1215185239

Cross-body linkage is showing that torsional shear (in the horizontal plane, parallel to the floor) is what you are creating -- while rotating in a perpendicular frame (the transverse plane).

While shiko is ostensibly presented as action in-plane (transverse rotation of the torso -- along the vertical plane cutting you into a front half and back half) the developed shear stress you just described defines a spiral action or potential (torque or moment) rotating in a horizontal plane perpendicular to the plane of the torso rotation.

What name do we use to describe a torque action created by shear on a plane perpendicular to a plane in which a rotation or applied moment is occurring?

Hint: it begins with the letter "G."

Since it is a spiral, it has both a horizontal aspect and a longitudinal aspect. If the longitudinal aspect of the spiral is expanding then the horizontal aspect is necessarily contracting, and vice versa. This is asagao, and also an aspect of chan si jing.

This does not necessarily dictate either tension or compression in either setting. A spiral may contract in one of these aspects because it is internally stressed in one way (tension) or because it is externally stressed in the opposite way (compression), or expand if it is given the opposite stresses, internally or externally, respectively. Because these are equivalent, the structure can react to relieve imposed stress (or to express that stress) on any axis allowed by the spiral(s) defined by the shear stress interaction.

Cordially,

Erick Mead
一隻狗可久里馬房但他也不是馬的.