Hindlimb SuspensionHindlimbImmobilizationMuscular AtrophyMuscle, SkeletalWeightlessness SimulationWeight-BearingMuscle Fibers, Slow-TwitchSuspensionsMuscle Fibers, Fast-TwitchMyosin Heavy ChainsEnzymes, ImmobilizedOrgan SizeMuscle Fibers, SkeletalAtrophyMuscle ProteinsRats, Sprague-DawleyAdaptation, PhysiologicalRats, WistarMuscle ContractionCells, ImmobilizedTime FactorsBody WeightTreponema Immobilization TestCasts, SurgicalImmobilized ProteinsRestraint, PhysicalRNA, MessengerIschemia