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Old 12-01-2006, 03:08 PM   #322
Erick Mead
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Dojo: Big Green Drum (W. Florida Aikikai)
Location: West Florida
Join Date: Jun 2005
Posts: 2,403
Re: Aikido: The learning of natural movement

Mike Sigman wrote:
For instance, your unnecessary addendum of "how" a bicycle might work in usage does nothing to assure me that you can actually ride a bicycle. ... What do you mean "propagation" or "conversion"?
Read above how the bike works ...
Mike Sigman wrote:
The mind leads the ki. I can form resultant force-vector paths that go out across the gap from my middle to my forearm and then, without moving shift it to my shoulderblade or to the sole of my foot, or whatever.
Of course -- like riding a bike --
Mike Sigman wrote:
I don't "resist" an incoming force; I simply vector-add to it in order to give me a resultant commensurate with what I want to do with Uke.
I thought we wanted to skip the higher maths. Will it be tensor equations next?

If I have your and Dan's description of the exercises right you are basically doing drills in using the joints' tensions as a kind of analog vector abacus. My issue is not with your method of computation or arrival at resultant, but the formal structure of the solution that you intend to compute.

If any component of your vector sum is parallel to and of opposite sign to the attacking vector you are addressing, you create one of two things:

1) If parallel but offset, a force couple in the plane (and either rotation or torque (if you apply countering leverage moment)), or

2) If parallel and in-line, a linear resisting thrust.

The principle of juji tells me that aikido technique is applied without any component of force in-line and directly resisting. Additive is permissible in linear parallel but not negative. A negative parallel componet of force (irimi) is not allowable unless it induces rotation (tenkan), ie. - is offset and forms a couple and thus potential rotation. Perpendicular components are allowed to directly engage to counter as they originate in rotation (tenkan). Negative parallel components (irimi) must be allowed to engage free of resisting moment or torque against the couple that results. Thus, are the two fundamental priniciples linked in my mind.

Potential rotation can be converted gyrodynamically if angular momentum in a complementary (90 degree) plane can be developed. (See the bike again). It can also develop torque if reaction force is allowed to develop. Axial torque resistance is the weakest aspect of almost any structure. As I interpret this, Aikijujtsu may well allow for the provocation and exploitation of that damaging axial torque -- and thus ground reaction is certainly in play as the reaction forms that torque against the rotation potential that is developed.

Aikido, in my mind, would interpret the sensation of developing torque as reaction or resistance, and once provoked, would shift juji (90 degrees) to convert that rotation potential (tenkan)or to initate further positive offset rotation (irimi) in a complementary plane.


Erick Mead
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