Fatigability of the elbow flexor muscles for a sustained submaximal contraction is similar in men and women matched for strength

The purpose of this study was to compare the time to task failure for a submaximal fatiguing contraction sustained with the elbow flexor muscles by men and women who were matched for strength ( n = 20, 18 - 35 yr). The maximal torque exerted at the wrist was similar for the men and women [ 64.5 +/- 8.7 ( SD) vs. 64.5 +/- 8.3 N . m; P > 0.05], which meant that the average torque exerted during the fatiguing contraction [ 20% of maximum voluntary contraction ( MVC)] was similar for the two sexes. The time to task failure was similar for these strength- matched men and women ( 819 +/- 306 vs. 864 +/- 391 s; P > 0.05). The mean arterial pressure was similar at the beginning of the contraction for men ( 97 +/- 12 mmHg) and women ( 96 +/- 15 mmHg; P > 0.05) and at task failure ( 134 +/- 18 vs. 126 +/- 26 mmHg; P > 0.05, respectively). Furthermore, the increases in heart rate, torque fluctuations, and rating of perceived exertion during the fatiguing contraction were similar for the two sexes. However, the electromyogram ( EMG) activity differed for the men and women: the rate of increase in the average of the rectified EMG (% peak MVC) for all the elbow flexor muscles was less for the women compared with the men ( P < 0.05). Furthermore, the bursts of EMG activity for the elbow flexor muscles increased toward exhaustion for all subjects but at a greater rate for the women compared with the men ( P > 0.05). The results indicate that strength- matched men and women experienced similar levels of muscle fatigue and cardiovascular adjustments during a sustained low- force isometric contraction, despite differences in the EMG activity for the two groups of subjects.