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muscle_mechanics

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内容提示: 1MUSCLE MECHANICSMuscle model 2Muscle tension and generation of joint torque 3Force on an external objectDepends on intensity of muscle activation, but also on “external leverage”.Good leverage: 4Bad leverage:In both examples, the force made by the hand on the shot was 70 N. With good leverage, this required 410 N of muscle tension. With bad leverage, the same job required 680 N of muscle tension. 5Question: Using a muscle tension of 680 N but good leverage, how heavy a shot wouldthe subject be able...

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1MUSCLE MECHANICSMuscle model 2Muscle tension and generation of joint torque 3Force on an external objectDepends on intensity of muscle activation, but also on “external leverage”.Good leverage: 4Bad leverage:In both examples, the force made by the hand on the shot was 70 N. With good leverage, this required 410 N of muscle tension. With bad leverage, the same job required 680 N of muscle tension. 5Question: Using a muscle tension of 680 N but good leverage, how heavy a shot wouldthe subject be able to hold?In the last two examples, the muscle tension was 680 N. With good leverage, this produced a 124 N force exerted on the shot. With bad leverage, this produced a 70 N force on the shot. 6Some conclusions about external leverage For a given force exerted on an external object, the better the external leverage,the smaller the muscle tension needed.  good for preventing injuries For a given muscle tension, the better the external leverage, the larger the forceexerted on an external object.  good for achieving high performance 7Some applications of leverage principles 8 9Factors that affect force exerted on an external objectFactors that affect muscle tension Amount of effortThe harder you try, the more tension the muscle can exert. 10 Speed of muscle shortening or lengtheningA muscle is able to exert a larger tension when it is not allowed to shorten at a fast rate. 11 12 13 Mechanical effect of stretching Muscle tension is increased. Reason: When a muscle is stretched, the parallel elastic component makes a large force. The effect is immediate. Muscle potentiation Muscle tension is increased. Reason: stretch reflex. The effect comes after a short lag. 14There is another type of muscle potentiation. It does not use the nervous system. Pre-tensionLimit in rate of muscle tension development creates a problem: Sub-maximal tension in early part of motion.Solution: Pre-tensing of muscle. 152 mechanisms for pre-tensing: Pre-tensing through mechanical restraint of motion Pre-tensing through “countermovement”

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