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Effect of standing or walking on physiological changes induced by head down bed rest: implications for spaceflight
J Vernikos1, D A Ludwig, A C Ertl
1Life Science Division, NASA Ames Research Center, Moffett Field, CA, USA.
Aviation, Space, and Environmental Medicine
|November 1, 1996
Summary
Intermittent standing or walking during head-down bed rest (HDBR) partially or fully prevented deconditioning. These interventions improved orthostatic tolerance and attenuated physiological losses, suggesting Gz force exposure is key.
Area of Science:
- Space physiology
- Human physiology
- Exercise physiology
Background:
- Head-down bed rest (HDBR) simulates microgravity effects.
- HDBR leads to significant physiological deconditioning.
- Preventing deconditioning is crucial for space missions.
Purpose of the Study:
- To evaluate intermittent passive (+1 Gz standing) and active (+1 Gz walking) interventions.
- To determine the effectiveness of these interventions in preventing HDBR-induced deconditioning.
- To assess the impact of exposure duration and frequency.
Main Methods:
- Nine male volunteers (30-50 years) underwent 4 days of 6° HDBR.
- Intervention groups performed periodic standing or walking for 2 or 4 hours daily.
- A control group remained in continuous HDBR (0 Gz).
Main Results:
- 4 hours of standing (S4) completely prevented loss of orthostatic tolerance.
- 2 hours of standing (S2) partially prevented decreases in orthostatic tolerance.
- Both walking and S4 attenuated decreases in peak oxygen uptake and plasma volume loss.
- Intermittent walking attenuated increased urinary calcium excretion.
Conclusions:
- Passive and active +1 Gz exposure differentially benefit physiological systems.
- Both duration and frequency of postural stimuli are important for mitigating deconditioning.
- Intermittent Gz force exposure is effective in preventing HDBR-induced deconditioning.