Quadriceps MuscleMuscle, SkeletalExerciseElectromyographyThighBicyclingMuscle Fibers, SkeletalPhysical EnduranceMuscle Fibers, Slow-TwitchWeight LiftingKneeMuscle Fibers, Fast-TwitchMyosin Heavy ChainsCitrate (si)-SynthaseLegOxygen ConsumptionMuscle ContractionMuscle FatigueMitochondria, MuscleIsometric ContractionPhysical ExertionBed RestGlycogenAnaerobic ThresholdKnee JointMuscle ProteinsResistance TrainingBiopsyTorqueLactic AcidMuscular AtrophyRunningExercise TestMuscle StrengthPhysical Education and TrainingPatellofemoral Pain SyndromePulmonary Gas ExchangeAdaptation, PhysiologicalMusclesFemoral NerveSpectroscopy, Near-InfraredPhysical FitnessWeightlessness CountermeasuresIsotonic ContractionPatellaPhosphocreatineBiomechanical PhenomenaPhosphofructokinasesAgingEnergy Metabolism3-Hydroxyacyl CoA DehydrogenasesMuscular DiseasesWeightlessness SimulationMyostatinPatellar LigamentInsulinTime FactorsMyofibrilsRestSciuridaeBlood GlucoseCarbonic Anhydrase IIIRecruitment, NeurophysiologicalDietary CarbohydratesSuccinate DehydrogenaseLocomotionAmino Acids, EssentialReference ValuesFatty Acids, NonesterifiedTendonsCapillariesGaitAnalysis of VarianceGlucose Clamp TechniqueRNA, MessengerRibosomal Protein S6 Kinases, 70-kDaMonocarboxylic Acid TransportersOxygenGlucoseSurgical FlapsImmobilizationRegional Blood FlowCreatine KinaseExercise ToleranceElectron Transport Complex IVHindlimbPhenylalanineHexokinaseGlucose Transporter Type 4Lower ExtremityGlycogen SynthaseCreatineHypertrophyDiaphragmPulmonary Disease, Chronic ObstructiveWalkingLactatesSatellite Cells, Skeletal MuscleCross-Over StudiesWeight-Bearing