Hindlimb SuspensionHindlimbMuscular AtrophyMuscle, SkeletalWeightlessness SimulationWeight-BearingMuscle Fibers, Slow-TwitchMuscle Fibers, Fast-TwitchSuspensionsMyosin Heavy ChainsOrgan SizeMuscle Fibers, SkeletalRats, Sprague-DawleyAtrophyMuscle ProteinsAdaptation, PhysiologicalRats, WistarMuscle ContractionIschemiaForelimbTime FactorsBody WeightLocomotionRNA, MessengerNeovascularization, Physiologic