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Old 04-20-2010, 05:58 AM   #38
Walter Martindale
Location: Cambridge, ON
Join Date: Jun 2006
Posts: 710
Re: Physical Tension - Another Thought

Oh dear...
Muscle contracts via an interaction between myosin and actin, in response to energy released by the ATP molecule splitting into ATP + P at the molecular level. This splitting is caused somehow by the release of calcium ions in the sarcoplasmic reticulum in response to an action potential, which itself is in response to a stimulus from a nerve - the stimulus having been based on a decision made either in the spinal cord (reflex) or the cerebral cortex to generate a movement...

(voluntary - or "striated") Muscles then shorten (contract) - they pull their ends closer together. In most cases both ends are attached to bones via tendons, in a configuration that is (if I remember correctly) most often a "class 3" lever system (fulcrum, force, load, (like the brachialis muscle pulling on the coronoid process of the ulna at the elbow) rather than force, fulcrum, load (like a crowbar) - which is a class 1 lever, or force, load, fulcrum - which is class 2 (like rowing)) When the muscle pulls on its tendons, it draws the points of attachment closer together, inducing movement of the bones. e.g., A relatively short movement of the insertion of the brachialis muscle causes a pretty large movement of the hand through elbow flexion. (the triceps muscle acting in opposition to brachialis could be called a class 1 lever - the triceps pulls on the olecranon process of the ulna, the fulcrum is the elbow joint, and the load is the hand)

In most cases, the brain induces motion via the muscles - when the brain isn't involved, it's some form of reflex.

Well trained aikido isn't a reflex, it is a conditioned response - stuff comes out without you having to think about it - kinda like Pavlov's dogs responding to a bell.
If things are going slowly enough, it's at a conscious level, but in most cases, if you have to think about what you're going, you're going to be going more slowly than if you "just do it" because you're making conscious decisions to act (more processing time involved) instead of allowing your body/brain to process what's going on at a subconscious "conditioned response" level much faster than you can think about it. "oh, wait - he's attacking with um - oh yeah - shomenuchi. I'd better get my arm up to receive...drat - too late, he hit me."

It has been a long time since I studied physiology so if the details are a little dodgy I apologise.

Last edited by Walter Martindale : 04-20-2010 at 06:02 AM. Reason: details, details - pedantic details.
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