Muscle FatigueFatigueMuscle, SkeletalMusclesMuscle ContractionMuscle Fibers, SkeletalElectromyographyIsometric ContractionFatigue Syndrome, ChronicMental FatigueQuadriceps MusclePhysical EnduranceRespiratory MusclesMuscle ProteinsMuscle, SmoothAbdominal MusclesNerve FibersMuscle Fibers, Fast-TwitchMuscle Fibers, Slow-TwitchMuscle, Smooth, VascularElectric StimulationTorqueMuscle DevelopmentBackExerciseMuscle WeaknessNeck MusclesMuscle RelaxationMuscle StrengthDiaphragmPhysical ExertionIntercostal MusclesDietary FiberTime FactorsMuscle DenervationElbowBiomechanical PhenomenaMuscular DiseasesLactic AcidMitochondria, MuscleExercise ToleranceMyocytes, Smooth MuscleOculomotor MusclesMuscle SpindlesMotor NeuronsMineral FibersBicyclingFemoral NerveMuscle, StriatedElectric Stimulation TherapyLumbosacral RegionExercise TestOxygen ConsumptionInhalationCalciumRunningMyographyPapillary MusclesLegIsotonic ContractionKneePhosphocreatineCotton FiberGlycogenAdaptation, PhysiologicalLocomotionHand StrengthMasseter MuscleProprioceptionMuscular AtrophyWeight-BearingMuscle CellsAnkle JointMyofibrilsSarcoplasmic ReticulumSpectroscopy, Near-InfraredLower ExtremityMasticatory MusclesFacial MusclesAnalysis of VarianceHeliumAction PotentialsMusculoskeletal SystemSignal Processing, Computer-AssistedRats, WistarMovementMyosin Heavy ChainsSatellite Cells, Skeletal MusclePsoas MusclesPostural BalanceStress FibersHindlimbEnergy MetabolismRegional Blood FlowTask Performance and AnalysisRespiratory MechanicsPectoralis MusclesUpper ExtremityPurkinje FibersRespiration