Bed RestHead-Down TiltWeightlessness SimulationWeightlessness CountermeasuresRestCardiovascular DeconditioningSpace FlightBedsWeightlessnessOxygen ConsumptionEnergy MetabolismOrthostatic IntoleranceTime FactorsBlood GlucoseMuscle, SkeletalLower Body Negative PressureInsulinExerciseMetabolismGlucosePhotic StimulationLactic AcidAdaptation, PhysiologicalBody Temperature RegulationFatty Acids, NonesterifiedMetabolomeFluorodeoxyglucose F18Heart RatePhysical ExertionLactatesBed OccupancyPositron-Emission TomographyBoidaeHormonesNitrogenMuscular AtrophySupine PositionEpinephrineAnalysis of VarianceStress, PhysiologicalOxygenPlasma VolumeReaction TimeEarly AmbulationGeneralization, StimulusAcoustic StimulationBody WeightPhysical EnduranceHypotension, OrthostaticFastingDietary CarbohydratesPhosphocreatineBody TemperatureVibrationGlucagonCocaExercise TestMagnetic Resonance ImagingPlasmodiophoridaMetabolomicsBlood PressureHypovolemiaLipid MetabolismHydrocortisonePhysical StimulationLegVisual PerceptionRadiopharmaceuticalsCold TemperatureGlycerolNorepinephrineDiscrimination LearningCardiovascular SystemRegional Blood FlowImmobilizationAmino Acids, EssentialAmino AcidsVascular CapacitanceKetone BodiesBrainDiscrimination (Psychology)HemodynamicsCardiac OutputMultimodal ImagingEatingDietary ProteinsBasal MetabolismPostprandial Period