There are many physiological benefits of being a woman. This is most obvious in the simplest measures of "physiological function": survival rate and Iifespan (1, 10, 15). Yet, longevity benefits conferred by the female sex do not appear to translate to whole body exercise performance. For example, women are slower than men in endurance events with distances <42 km (or 26.2 miles), i.e., regular marathon. Metabolism is among the physiological factors that contribute to survival and exercise performance. Several studies have shown sex differences in metabolism at rest and during exercise. This is particularly interesting because mitochondria take center stage in metabolic homeostasis. The notion of sex differences in mitochondrial function and metabolic homeostasis is now strengthened by the study by Miotto et al. (12) that appears in Am J Physiol-Regulatory, Integrative and Comparative Physiology. The study is an important step toward understanding mechanisms underlying sex differences in metabolism, with potential implications for exercise performance. Among several relevant findings, the study by Miotto and colleagues shows that women skeletal muscle have 7) higher inhibition of mitochondrial fatty acid metabolism by malonyl-CoA, 2) greater abundance of the fatty acid transporter CD36, and 3) lower ADP sensitivity of mitochondrial respiration.
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