Quadriceps MuscleMuscle StrengthElectric Stimulation TherapyBody Mass IndexMuscle, SkeletalMusclesMuscle Strength DynamometerMuscle WeaknessThighMuscle ContractionMuscle FatigueIsometric ContractionRespiratory MusclesTorqueMuscle ProteinsMuscle Fibers, SkeletalKneeKnee JointMuscle, SmoothExerciseObesityElectromyographyMuscle, Smooth, VascularMuscle DevelopmentLegFemoral NerveBiomechanical PhenomenaMuscular AtrophyHand StrengthPhysical EnduranceMuscle Fibers, Slow-TwitchMuscular DiseasesRisk FactorsPatellaWeight LiftingTime FactorsBody CompositionExercise TherapyMuscle Fibers, Fast-TwitchMitochondria, MuscleRange of Motion, ArticularCross-Sectional StudiesAnterior Cruciate LigamentOsteoarthritis, KneeBody WeightKnee InjuriesExercise TestResistance TrainingAbdominal MusclesOxygen ConsumptionMuscle DenervationOverweightProspective StudiesAnthropometryAnalysis of VarianceGaitMotor ActivityTendonsElectric StimulationNeck MusclesCase-Control StudiesAgingPhysical ExertionPatellar LigamentWeight-BearingCohort StudiesMyocytes, Smooth MusclePhysical FitnessImmobilizationMyostatinMuscle, StriatedAge FactorsOculomotor MusclesRegression AnalysisTreatment OutcomeJoggingTensile StrengthMuscle RelaxationThinnessMuscle SpindlesWalkingRecovery of FunctionLinear ModelsSex FactorsBicyclingPulmonary Disease, Chronic ObstructiveArtificial OrgansBody HeightFollow-Up StudiesJoint InstabilitySeverity of Illness IndexPatellofemoral Pain SyndromeSarcopeniaPatellofemoral JointLongitudinal StudiesPapillary MusclesAdaptation, PhysiologicalAdipose TissueArthroplasty, Replacement, KneeMotor Neurons