Bed RestHead-Down TiltWeightlessness SimulationBedsWeightlessness CountermeasuresRestCardiovascular DeconditioningSpace Flightcdc42 GTP-Binding ProteinWeightlessnessInfant EquipmentOrthostatic Intolerancecdc42 GTP-Binding Protein, Saccharomyces cerevisiaeOpen BiteLower Body Negative PressureInfant CareInfant, Prematurerac GTP-Binding ProteinsBed OccupancyInfant, Very Low Birth WeightSupine PositionInfant MortalityMuscular AtrophyIntensive Care Units, NeonatalInfant, NewbornPlasma VolumeEarly AmbulationMuscle, SkeletalExerciseMAP Kinase Kinase KinasesHypotension, OrthostaticPregnancy-Associated Plasma Protein-AHypovolemiaTime FactorsMiocamycinVascular CapacitanceAmino Acids, EssentialBacteriophage muImmobilizationGestational Age