Senefeld, J., Yoon, T., Bement, M. H., & Hunter, S. K. (2014). Sex differences in fatigue during dynamic contractions differ between arm and leg muscles. Presentation 1014 at the 59th Annual Meeting of the American College of Sports Medicine, San Francisco, California; May 29-June 2, 2012.

This study compared the muscle fatigue in men and women during repeated submaximal dynamic load contractions at maximal velocity in arm and leg muscles. Men (N = 14) and women (N = 19) attended two separate sessions to test dynamic fatigue of the elbow flexor muscles and knee extensor muscles on the Biodex System 4 Pro dynamometer. For each maximal velocity dynamic contraction, Ss moved the limb concentrically through a 90° range of motion at maximal velocity with a load equivalent to 20% of maximal voluntary isometric contraction force. This cycle was repeated every three seconds for three sets of 30 contractions. Maximal voluntary isometric contractions were performed at the start of the session and immediately after the set of 30 contractions.

Men were stronger than women for both elbow flexion and knee extension. Maximal voluntary isometric contractions decreased with the dynamic fatiguing contractions in both sessions. The relative decline was greater for the elbow flexors than the knee extensors and was greater for men in knee extension. There was no gender difference in maximal voluntary isometric contractions decline for the elbow flexors. Initial maximal contraction speed in elbow flexion was faster for men than women, but similar in knee extension. Maximal contraction speed decreased during the repeated maximal velocity dynamic contractions in both sessions. The relative decline was greater for the elbow flexors than the knee extensors. Maximal speed declined similarly for men and women with the elbow flexors but was greater for women than men with the knee extensors.

Implication. After experiencing submaximal dynamic contractions at maximal voluntary speed it was concluded that: 1) elbow flexor muscles were more fatigable than knee extensors; 2) in contrast to sustained isometric contractions there was no gender difference in fatigue for elbow flexor muscles, and 3) the gender difference in knee extensor muscles varied depending on the measurement task.

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