The effect of repeated weightlessness exposures on maximal aerobic capacity was determined when seven healthy men (36-48 yr) underwent two 10-d bedrest (BR) periods in the -6° headdown position, which were separated by a 14-d recovery period. No prescribed exercise was performed by the subjects during the course of the experiment. A graded supine cycle ergometer test consisting of 4 min of unloaded pedaling at 60 rpm followed by increased work rate of 15 W.min-1 until volitional fatigue (max) was performed before (pre) and after (post) the first and second BR periods, i.e., BR1 and BR2, and again 14 d after BR2 (REC). During exercise, submaximal and maximal oxygen uptake (VO2), ventilation (VE), heart rate (HR), systolic (SBP) and diastolic (DBP) blood pressures were measured and the gas exchange anaerobic threshold (AT) was determined. Plasma volume (Vp, T-1824) and body composition were measured pre- and post-BR1 and BR2 and following REC. Compared to the respective pre-BR control values, VO2max decreased (p < 0.05) by 8.7% after BR1 and 5.2% after BR2 but returned to pre-BR values following 14 d REC. Submaximal and maximal HR increased (p < 0.05) post-BR1 and BR2 but returned to pre-BR levels after REC. The AT and Vp decreased (p < 0.05) post-BR1 and BR2 but returned to pre-BR levels after REC. Body weight increased (p < 0.05) gradually during the experiment and did not return to control values. With regard to muscle work performance, these data suggest that 2 weeks of minimal activity are adequate for complete recovery from simulated weightlessness and that repeated exposure can be safely tolerated.
|Original language||English (US)|
|Number of pages||7|
|Journal||Aviation Space and Environmental Medicine|
|State||Published - 1985|
ASJC Scopus subject areas
- Public Health, Environmental and Occupational Health