Muscle ContractionIsometric ContractionMuscle, SkeletalElectromyographyMusclesElectric StimulationPhosphocreatineMuscle FatigueIsotonic ContractionTorqueMyocardial ContractionUterine ContractionAdenosine TriphosphateElbowModels, BiologicalRecruitment, NeurophysiologicalMuscle, SmoothMuscle Fibers, SkeletalMotor NeuronsKneeMuscle StrengthMuscle RelaxationSarcomeresBiomechanical PhenomenaCalciumMusculoskeletal Physiological PhenomenaVasoconstrictionPhysical EnduranceMyosinsTime FactorsVolitionPapillary MusclesPsoas MusclesQuadriceps MusclePhysical ExertionMuscle, Smooth, VascularRana temporariaGuinea PigsMyographyPotassium ChlorideRabbitsPhenylephrineStress, MechanicalAnkle JointMuscle SpindlesMyofibrilsDose-Response Relationship, DrugElasticityVasoconstrictor AgentsThighAcetylcholineTracheaAction PotentialsNorepinephrineRana esculentaEvoked Potentials, MotorLegAnuraAorta, ThoracicTendonsFingersMyosin Light ChainsRats, WistarMuscle Strength DynamometerCatsHandForearmReflex, StretchHand StrengthMotor CortexExerciseElbow JointThumbArmRats, Sprague-DawleyKnee JointMovementWeight-BearingFemoral NerveDogsHindlimbGastrointestinal MotilityNeural ConductionReflexAnalysis of VarianceMasseter MuscleHeart RateMuscle TonusFeedback, SensoryBupranololActinsUrinary BladderAdaptation, PhysiologicalEnergy MetabolismPeristalsisTranscranial Magnetic StimulationIsoproterenolHeartBlood PressureAtropine