Slide 1Slide 2Slide 3Sliding Filament TheoryLength-tension RelationshipSlide 6Velocity-tension RelationshipMotor Unit = Neuron and all muscle fibers it innervatesSynapse = gap between neuron and muscle fiberTypes of Motor UnitsMotor Unit ContractionTypes of ContractionMotor Unit Recruitment Size principle = Orderly, small to largeTrainingEnergy MetabolismSlide 16Work-Rest CyclingIE 5531IE 553 Engineering of Human WorkDr. Andris FreivaldsClass #2IE 5532IE 553 Engineering of Human WorkDr. Andris FreivaldsClass #2IE 5533Muscle StructureIE 5534Sliding Filament Theory•Thick & thin filaments slide over one another•Shortening distance between z-lines•Crossbridges - bonds between myosin head and globular actin•Requires energy in form of ATP molecule•Initiated by Ca++ ions releasing inhibition•Produce several basic propertiesIE 5535Length-tension RelationshipTension greatest at midrangeIE 5536•Weightless astronaut •Relaxed posture•No muscle forceWhere is midrange?IE 5537Velocity-tension RelationshipTension greatest at slow motions (isometric tension)IE 5538Motor Unit =Neuron and all muscle fibers it innervatesAll-or-none principleInnervation ratioIE 5539Synapse = gap between neuron and muscle fiberIE 55310Types of Motor UnitsIE 55311Motor Unit ContractionIE 55312Types of Contraction•Isometric = constant length (static)•Isotonic = constant force (dynamic)–Concentric = muscle shortens–Eccentric = muscle lengthens–Isokinetic = constant velocity–Isoinertial = constant accelerationIE 55313Motor Unit RecruitmentSize principle = Orderly, small to largeIE 55314TrainingIE 55315Energy MetabolismATP = adenosine triphosphate, CP = creatine phophateAerobically (with O2) = glucose + 6O2 → 6H2O + 6CO2 +38ATPAnaerobically (no O2) = glucose → 2 lactate + 2ATPIE 55316Fatigue and Endurance TimesT(sec) = 1236.5 – 72.5 (%max–15)0.618IE 55317Work-Rest
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