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Old 11-27-2012, 11:07 AM   #170
Walter Martindale
Location: Cambridge, ON
Join Date: Jun 2006
Posts: 679
Re: Is aiki a clash of forces?

"It's Just Physics" Well... When I was studying biomechanics - post-grad - we were shown a film (not video) describing the study of the optimisation of a human movement.

The movement was kicking an object that was suspended at approximately waist height, about one straight leg's length away from the subject in the study.

Variables included (but were not limited to because I don't have the original document available) - neural transmission rates, muscular contraction velocities, position of the origin and insertion points of ALL the muscles involved in the motion, inertial characteristics of the limb doing the kicking, and on, and on, and on.

The computed "optimal movement" also required that the person have a weight tied to his foot so that he'd slow down enough for the available technology to obtain data (and the weight was included in the optimisation calculation). The subject in the study was standing on one leg, strapped in place so he could only move the leg being studied.

The optimization/model software was described something like - (more than 30) ordinary differential equations and (about 30) variables, requiring 27 hours computing with a PDP11 computer (it was the 1970s, a 1990s 386 could probably whip this off in an hour or so)

The subject in the study was able to learn the movement and actually match the movement predicted by the "optimised" model.

Now - take a free-standing human. 208 bones (IIRC), all them muscles (all them different contractile properties from fast twitch to slow twitch), neural transmission rates, reflex loops, ion channels for repolarization of a nerve or muscle surface, and it comes down to physics - from the neural depolarizations that happen in the brain when the decision is made to move, the action potential jumping down the axons via electro-chemical reactions (physics), to the chemicals crossing the synapses at the end of the nerves and stimulating the muscle, to the calcium ions travelling through the sarcoplasmic reticulum into the muscle fibre stimulating the muscle fibre to contract, to the ATP being split to ADP+P+energy which causes the muscle to contract at the microscopic level, to the tendon being pulled by the contracting muscle, and eventually to the surface of the limb that's being moved by the muscle contraction - all of it - ALL is caused at some stage by "physics" - the interaction of molecules (some call it chemistry, too, but even chemistry depends on the "physics" of the atomic and molecular shapes/sizes/bonds to make things move.

Just because ithe human body is a REALLY complex machine that is VERY difficult to explain in complete detail doesn't make it magic. It's Physics, but we humans haven't figured out how to explain it all in those terms - so we make up magical things about people who have achieved a standard of ability greater than ours. (or do we call them "gods"?)

Last edited by Walter Martindale : 11-27-2012 at 11:19 AM.
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