Changes in skeletal muscle in males and females following endurance training

Gender differences in substrate selection have been reported during enduran ce exercise. To date, no studies have looked at muscle enzyme adaptations f ollowing endurance exercise training in both genders. We investigated the e ffect of a 7-week endurance exercise training program on the activity of be ta-oxidation, tricarboxylic acid cycle and electron transport chain enzymes , and fiber type distribution in males and females. Training resulted in an increase in (V) over dot O-2 peak for both males and females of 17% and 22 %, respectively (P < 0.001). The following muscle enzyme activities increas ed similarly in both genders: 3-beta -hydroxyacyl CoA dehydrogenase (38%), citrate synthase (41%), succinate-cytochrome c oxidoreductase (41%), and cy tochrome c oxidase (COX; 26%). The increase in COX activity was correlated (R-2 = 0.52, P < 0.05) with the increase in (V) over dot O-2peak/ fat free mass. Fiber area, size, and % area were not affected by training for either gender, however, males had larger Type II fibers (P < 0.05) and females ha d a greater Type I fiber % area (P < 0.05). Endurance training resulted in similar increases in skeletal muscle oxidative potential for both males and females. Training did not affect fiber type distribution or size in either gender.