The male study was NASA-sponsored and performed in the Campaign 1 study at University of Texas Medical Branch in Galveston, Texas. The female study was performed as part of the Women International Space Simulation for Exploration (WISE) study, a 60-day bed rest study and joint venture between the European Space Agency (ESA), the French space agency (CNES), the National Aeronautics and Space Administration (NASA) and the Canadian Space Agency (CSA). It was conducted by MEDES, the French Institute for Space Medicine and Physiology, in the clinical research facility at the Rangueil Hospital in Toulouse, France.
Hypothesis 1: 60 days of bed rest will result in an increased incidence of changes in menstrual cycle length that would be further exasperated by the use of intense exercise and dietary changes as countermeasures.
Subjects were served as to their menstrual history over 90 days prior to the initiation of the study. All subjects had normal cycle lengths, 31±0.8 days. One subject (4%) had a lengthening of her cycle (=45 days) during the control phase of the study. Over the bedrest period, 8 subjects (33%) had a lengthened cycle (p<0.05) with a mean of 62±8.2 days. There was no change in the timing of the LH surge prior to menses or in the duration of menses in these subjects. During bed rest there is an increased incidence of menstrual cycle dysfunction (oligomenorrhea) that was not significantly related to the countermeasures. The lengthening of menstrual cycle during bedrest is a result of a delay in ovulation due to the absence of a LH surge (ovulation) associated with lower progesterone and estrodiol levels.
Hypothesis 2: Subjects with lengthened cycles would have a greater level “stress” associated with increases in urinary cortisol concentrations, and in basal heart rate and body temperature. Over the course of bedrest there were no differences in basal heart rate, mean arterial pressure or body temperature between subject with a normal cycle (n=16) and those who were oligomenorrheic (n=8). Urinary cortisol excretion rates were similar between groups. A greater level of “stress” did not appear to be a contributing factor thus other factors known to contribute to cycle lengthening were investigated. There were no differences in caloric intake or body mass distribution. Thus the mechanisms contributing to the delay in ovulation due to the absence of a LH surge (ovulation) associated with lower progesterone and estrodiol levels during bedrest are unclear.
Hypothesis 3: In the presence of cycle lengthening the effects of bed rest on loss of bone and lean body mass would be accentuated, as would be reductions in muscle strength, aerobic capacity and orthostatic tolerance.
There were no significant group differences in body mass, composition, bone mass, muscle strength or orthostatic tolerance between subject with a normal cycle (n=16) and those who were oligomenorrheic (n=8). However, subjects who were oligomenorrheic had a greater reduction in maximum oxygen consumption, 24% than those with a normal cycle 17%. There was no influence of countermeasure group. Therefore, the impact of changes in menstrual cycles on responses to bedrest may confound the efficacy of countermeasures.
Male study: results for this study are not available.
|Mission||Launch/Start Date||Landing/End Date||Duration|
|Campaign 1||08/29/2004||11/21/2004||84 days|