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47 knes 462 fk 08 the froce your muscele create during

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Unformatted text preview: muscle fiber is correlated with axonal conduction speed. 47 KNES 462 ©FK ‘08 the froce your muscele create during motor activities--its not a binary signal off or on- you cant tune the force over a very whide range The Motor Unit: Force Grading I • Two ways to grade force of muscle contraction: – recruitment of muscle cells is ranked (size principle): 2 mechanisms • slow units first, respond to weak synaptic input • fast fatigue-resistant next size principal--- the slow twitch activate first.then int--then fast twitch • fast fatigable last modulation--at 100 hz the muscel goes into fused tetonous-- aka muscel cramp. – modulation of firing rate of motor neurons: • lowest firing rates for steady contraction: ~ 8 Hz • higher rates for more intense contractions: ~ 25-80 Hz 48 KNES 462 ©FK ‘08 The Motor Unit: Force Grading II • Other scenario: constant low force needed over long period of time – Approx. half of muscle fibers are active; – With ongoing contraction, some fatigue, and some ‘rested’ ones jump in and assist; – Fast fatigue resistant fibers are additionally recruited ; – Large units (fast fatigue) kick in; – This scenario is only valid for fairly low contraction only works if blood flow is not affected forces (<25% maximum voluntary muscle contraction [MVA]) 49 KNES 462 ©FK ‘08 KNES 462 The Motor Unit: Size Principle 50 KNES 462 ©FK ‘08 recpetor-records the state of something Sensors / Receptors 53 KNES 462 ©FK ‘08 Muscle Receptors they are called proprioceptors--...
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This document was uploaded on 03/19/2014 for the course KNES 462 at Maryland.

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