Hindlimb SuspensionWeightlessness SimulationHindlimbMuscular AtrophySuspensionsMuscle, SkeletalWeight-BearingMuscle Fibers, Slow-TwitchMuscle Fibers, Fast-TwitchMyosin Heavy ChainsOrgan SizeMuscle Fibers, SkeletalIschemiaRats, Sprague-DawleyAtrophyLimb BudsRats, WistarMuscle ProteinsAdaptation, PhysiologicalForelimbMuscle ContractionExtremitiesTime FactorsBody WeightLocomotionRNA, Messenger