Sex differences in contractile properties and fatigue resistance of human skeletal muscle

Wüst, Robert C.I., Morse, Christopher I., Haan, Arnold de, Jones, David A. and Degens, Hans (2008) Sex differences in contractile properties and fatigue resistance of human skeletal muscle. Experimental physiology, 93 (7). pp. 843-850. ISSN 0958-0670

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Abstract

To explore the cause of higher skeletal muscle fatigue resistance in women than men, we used electrically evoked contractions (1-s on 1-s off, 30 Hz, 2 min), which circumvents motivational bias and allows examination of contractile properties. We compared 29 men (26.5 (7.0) yr) (mean (SD)) with 35 women (25.4 (7.6) yr). Strength of the quadriceps muscle was higher in men than women (P<0.001). The lower maximal rate of relaxation in women (P=0.002) indicates that their muscles were slower than those of men. The torque declined less in women than in men (37.7 (10.7)% vs. 29.9 (10.0)%; P=0.002), and was not related to muscle strength or size, as determined with MRI. The sex-difference in fatigability was also seen when the circulation to the leg was occluded (torque declined 76.9 (10.8) vs. 59.5 (16.9)% in men vs. women respectively; P=0.008). The maximal rate of relaxation correlated with the fatigability of the muscle under all conditions (correlations ranging from 0.34 to 0.51, P<0.02). We conclude that the sex-related difference in skeletal muscle fatigue resistance is not explicable by differences in motivation, muscle size, oxidative capacity and/or blood flow between sexes, but might be related to differences in fiber type composition.