Sex-Specific Effects on Exercise Metabolism

Women and men exhibit different anthropometric and physiologic characteristics, along with a sex-specific morphologic and metabolic imprint of skeletal muscle. These sex differences integrate to impact on metabolism during exercise. Men have a greater maximal exercise capacity than equally trained women. Besides this, a remarkable sex difference is a greater fatty acid oxidation in women than men at the same relative exercise intensity. The greater fatty acid oxidation may lead to less amino acid oxidation during exercise and potentially muscle glycogen sparing in women compared with men. Several sex-specific morphologic and molecular features of skeletal muscle appear to explain the differences in substrate utilization during exercise in women and men. Here, factors such as muscle fiber type composition, capillarization, and substrate availability within skeletal muscle will be discussed in a sex-comparative manner. The influence of sex on mitochondria—specifically, the energy generating pathways as beta-oxidation and glycolysis, the tricarboxylic acid cycle (TCA) cycle, and electron transport chain capacities—will also be reviewed.