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Response to muscular exercise following repeated simulated weightlessness
Aviation, Space, and Environmental Medicine
|June 1, 1985
Summary
Repeated weightlessness exposures significantly reduce maximal aerobic capacity and plasma volume, but these effects are reversible with recovery. Exercise is not required for recovery of aerobic fitness after bed rest.
Area of Science:
- Space Physiology
- Cardiovascular Physiology
- Exercise Physiology
Background:
- Spaceflight necessitates understanding the physiological deconditioning caused by weightlessness.
- Bed rest is a common analog for studying the effects of microgravity on the human body.
Purpose of the Study:
- To investigate the impact of repeated simulated weightlessness on maximal aerobic capacity.
- To determine if recovery occurs after multiple exposures to bed rest.
Main Methods:
- Seven healthy men underwent two 10-day bed rest periods with a 14-day recovery in between.
- Maximal aerobic capacity (VO2max), heart rate, blood pressure, and anaerobic threshold were assessed using graded cycle ergometry.
- Plasma volume and body composition were also measured.
Main Results:
- VO2max decreased after each bed rest period but returned to baseline after recovery.
- Heart rate and anaerobic threshold showed similar patterns of decrease and recovery.
- Plasma volume decreased post-bed rest, while body weight increased.
Conclusions:
- Repeated short-duration weightlessness exposures cause reversible deconditioning of maximal aerobic capacity.
- Recovery of aerobic fitness and plasma volume is possible after bed rest without prescribed exercise.
- The findings have implications for astronaut health during long-duration space missions.