Muscle FatigueFatigueMuscle, SkeletalMusclesMuscle ContractionCell HypoxiaIsometric ContractionMuscle ProteinsElectromyographyMuscle Fibers, SkeletalMyocardiumFatigue Syndrome, ChronicPhysiologyAnoxiaMental FatigueHeartMyocytes, CardiacQuadriceps MuscleMuscle, SmoothPhysical EnduranceRespiratory MusclesAbdominal MusclesMuscle, Smooth, VascularPapillary MusclesMuscle DevelopmentTime FactorsMyocardial ContractionElectric StimulationExerciseTorqueBackCalciumMuscle RelaxationMuscle WeaknessCardiac OutputNeck MusclesMuscle StrengthOxygenDiaphragmPhysical ExertionMuscle Fibers, Fast-TwitchMyofibrilsMuscle Fibers, Slow-TwitchSarcomeresOxygen ConsumptionIntercostal MusclesMuscular DiseasesHypoxia, BrainSarcoplasmic ReticulumLactic AcidBiomechanical PhenomenaHeart VentriclesArrhythmias, CardiacRabbitsMitochondria, MuscleElbowMuscle DenervationCells, CulturedMyocytes, Smooth MuscleExercise ToleranceRats, Sprague-DawleyAdaptation, PhysiologicalRats, WistarTroponin CCardiac Surgical ProceduresExercise TestFetal HypoxiaCardiomegalyMuscle CellsTroponinDeath, Sudden, CardiacRNA, MessengerModels, BiologicalTroponin IAction PotentialsBicyclingRespirationPhosphocreatineOculomotor MusclesEnergy MetabolismInhalationAnalysis of VarianceFemoral NerveMotor NeuronsGlycogenMuscle, StriatedDogsElectric Stimulation TherapyMyosin Heavy ChainsHypoxia-Inducible Factor 1, alpha SubunitAdenosine TriphosphateCardiac MyosinsSarcolemmaRunningMuscle SpindlesHeart RateLumbosacral RegionCardiomyopathiesAgingLeg