EFFECTS OF GENDER ON RESTING LEG BLOOD-FLOW - IMPLICATIONS FOR MEASUREMENT OF REGIONAL SUBSTRATE OXIDATION

These studies were designed to examine whether the respiratory quotien t (RQ) of leg tissue (primarily skeletal muscle) would increase to a g reater degree in women than in men during meal ingestion. We found tha t mean leg and systemic RQ values were similar in men under both basal and fed conditions, whereas the agreement was poor in women. In women , leg RQ values tended to be greater than the systemic RQ, whereas spl anchnic RQ values tended to be lower than the systemic RQ. The possibi lity that measurement imprecision accounted for the different findings in women could not be excluded because the arteriovenous blood O-2 di fferences were almost twice as great in men as in women (53.7 +/- 5.4 vs. 28.6 +/- 2.9 ml of O-2/l, respectively; P < 0.01), as were venoart erial blood CO2 differences. The smaller arteriovenous differences in women appeared to limit our ability to accurately measure their leg RQ values. O-2 uptake relative to leg fat-free mass (FFM) was not differ ent between men and women, whereas leg blood flow relative to leg FFM was greater in women than in men (55 +/- 3 vs. 39 +/- 2 ml.kg FFM-1.mi n(-1), respectively; P < 0.001). These findings were confirmed by exam ining data from other studies conducted in our laboratory to create a larger data set. We conclude that resting leg blood flow in women is g reater (relative to FFM) than in men, making it more difficult to accu rately measure leg RQ in women.