Bed RestBed OccupancyHead-Down TiltWeightlessness SimulationBedsWeightlessness CountermeasuresLength of StayRestCardiovascular DeconditioningHospitalizationSpace FlightEnglandWeightlessnessHealth Care CostsOrthostatic IntoleranceLower Body Negative PressureUnited StatesProspective StudiesRetrospective StudiesPhysiciansMedical Staff, HospitalHospital Bed CapacitySupine PositionMuscular AtrophyPhysician-Patient RelationsEarly AmbulationPlasma VolumeMuscle, SkeletalTime FactorsExerciseHypotension, OrthostaticAttitude of Health PersonnelHypovolemiaBedbugsFamily PracticeVascular Capacitance