Bed RestBone and BonesHead-Down TiltWeightlessness SimulationWeightlessness CountermeasuresRestBone RemodelingCardiovascular DeconditioningBone DensitySpace FlightBone ResorptionBedsWeightlessnessBone MarrowBone NeoplasmsBone DevelopmentBone Marrow CellsOrthostatic IntoleranceBone DiseasesLower Body Negative PressureBone RegenerationBone MatrixBone Marrow TransplantationBone TransplantationPhysiciansMedical Staff, HospitalTime FactorsBed OccupancyBone SubstitutesFractures, BoneBone Diseases, MetabolicBone Morphogenetic ProteinsPhysician-Patient RelationsMuscular AtrophyMuscle, SkeletalSupine PositionExerciseEarly AmbulationPlasma VolumeHypotension, OrthostaticBone Morphogenetic Protein 2Attitude of Health PersonnelOsteogenesisTemporal BoneHypovolemiaFamily PracticeImmobilizationVascular CapacitanceAmino Acids, EssentialParietal BoneFemur