Sex differences of physical working capacity in normoxia and hypoxia.

Abstract

A balanced Latin square design examined sex differences in working capacity for four endurance tasks involving different volumes of muscle (two-leg, one-leg, arm plus shoulder and arm ergometry) in eight women and eight men under normoxic and hypoxic (12% oxygen) conditions. There was a substantial (30-40%) sex difference in maximum oxygen intake during two-leg ergometry. Much of the difference was size related. The discrepancy was reduced by expressing data per litre of active leg muscle, and (more simply) was largely eliminated if expressed per kilo of skinfold-estimated fat-free body mass. However, a part of the sex discrepancy in the performance of two-leg ergometer work arose from a limitation of oxygen transport in the female. The balance thus shifted progressively in favour of the women in tasks that involved a smaller proportion of the total body mass. Likewise, hypoxia exacerbated the female disadvantage in large muscle but not in small muscle tasks. From the viewpoint of physical employment, the...