Bed RestHead-Down TiltWeightlessness SimulationWeightlessness CountermeasuresRestCardiovascular DeconditioningSpace FlightBedsWeightlessnessOrthostatic IntoleranceLower Body Negative PressurePractice Guidelines as TopicHealth Planning GuidelinesExerciseBed OccupancyGuidelines as TopicSupine PositionTime FactorsMuscular AtrophyEvidence-Based MedicineMuscle, SkeletalPlasma VolumeEarly AmbulationUnited StatesGuideline AdherenceHypotension, OrthostaticAdvisory CommitteesHypovolemiaAmino Acids, EssentialVascular CapacitanceImmobilizationSpinal PunctureSocieties, MedicalConsensus