Gender specific changes in muscle mass with long‐term bedrest

Abstract

Because few women have been studied, it is not known if gender specific responses to real or simulated spaceflight exist. We monitored muscle volume changes of the thigh (quadriceps femoris) and calf (triceps surae) of women and men exposed to 60 and 90 days of -6° head down tilt (HDT) bedrest (BR), respectively. Magnetic resonance imaging measurements were made pre-BR, HDT29, HDT57 (women), and HDT89 (men). The women lost relatively more (P<0.05) thigh muscle volume than the men after one month (−17±1 vs. −10±1%). This amount of loss for the women at one month was similar (P>0.05) to the amount the men had lost in three months (−18±1%). The women also had lost relatively more (P<0.05) thigh muscle volume in two months (−21±1%) than the men had lost in three months. The women tended (P=0.08) to lose relatively more calf muscle volume in one month than the men (−18±1 vs. −16±1%), while the women had lost as much (P>0.05) calf muscle volume after two months (−29±1%) as the men had lost after three months (−29±2%). These results suggest that women are more susceptible to bedrest-induced muscle loss than men and countermeasures specific to women will likely need to be developed. Sponsors: NASA, ESA, CNES