Sex- and Mode-specific Responses to Eccentric Muscle Fatigue

The primary purpose of the present investigation was to examine sex-related differences as a result of fatiguing eccentric muscle actions on torque, muscle blood flow, electromyography, and mechanomyography. Eighteen men and 18 women performed peak torque trials prior to (pretest), immediately after (posttest), and 5-min after (recovery) completing 50 submaximal (60% of eccentric peak torque), eccentric, isokinetic (180°·s -1) muscle actions of the elbow flexors. Electromyographic and mechanomyographic responses were simultaneously recorded from the biceps brachii muscle, and muscle blood flow was measured at pretest, posttest and recovery. There were sex- and mode-specific responses for torque, but there were no sex-specific muscle blood flow or neuromuscular responses. From pretest to posttest, torque decreased (80.0-88.2% of pretest) for both the men and women. At recovery concentric peak torque recovered to a greater extent in women (95.0% of pretest) than men (88.0% of pretest), while eccentric peak torque recovered to a greater extent in men (88.9% of pretest) than women (86.9% of pretest). The sex-specific torque responses were not associated with different motor control strategies or differences in the occlusion of muscle blood flow between the men and women. For both men and women, eccentric fatiguing exercise is manifested similarly during isometric muscle actions, but not during eccentric and concentric muscle actions.