Muscle ContractionMuscle, SkeletalTorqueIsotonic ContractionMuscle FatigueElectromyographyMuscle StrengthMusclesBiomechanical PhenomenaSarcomeresElectric StimulationHand StrengthMuscle RelaxationKneeRana temporariaMuscle Fibers, SkeletalElbowPsoas MusclesPhysical ExertionMuscle Strength DynamometerMyosinsPapillary MusclesExerciseMusculoskeletal Physiological PhenomenaPhysical EnduranceVolitionMyocardial ContractionTime FactorsRecruitment, NeurophysiologicalMyographyQuadriceps MuscleStress, MechanicalVasoconstrictionCalciumMotor NeuronsMovementLegMuscle, SmoothRabbitsRana esculentaAnuraElasticityKnee JointFingersTendonsAnkle JointThighMuscle, Smooth, VascularPhosphocreatineRange of Motion, ArticularArmMuscle TonusMuscle Fibers, Fast-TwitchVasoconstrictor AgentsVasodilationHeart RateElbow JointAdenosine TriphosphatePhenylephrinePotassium ChlorideAcetylcholineBlood PressureMuscle WeaknessMuscle SpindlesTetanyHindlimbWeight-BearingModels, BiologicalDose-Response Relationship, DrugMyosin Light ChainsMuscle Fibers, Slow-TwitchAorta, ThoracicVasodilator AgentsEvoked Potentials, MotorTracheaReflex, StretchMotor CortexForearmEndothelium, VascularAnalysis of VarianceActomyosinHeartDiaphragmWristThumbRana pipiensNorepinephrineRegional Blood FlowHolothurinPhosphatesNeck MusclesMuscle Stretching ExercisesArteriesAdaptation, PhysiologicalAchilles TendonDogsEnergy MetabolismReflexAgingRats, Wistar