MUSCLE ENDURANCE OF THE ELBOW FLEXOR MUSCLES IN MEN AND WOMEN MATCHED FOR STRENGTH

Abstract

The endurance time for a submaximal isometric contraction with the elbow flexor muscles is longer in women than men and is related to a lower target force and reduced pressor response in the women (Hunter & Enoka, JAP, 91: 2686, 2001). PURPOSE To compare the endurance times of the elbow flexor muscles for sustained and intermittent isometric contractions in men and women matched for strength. METHODS Seven men (mean SE, 20 1 yr) and five women (23 2 yr) performed two submaximal isometric contractions until exhaustion on separate days: (1) a sustained isometric contraction at 20% of maximal voluntary contraction (MVC) force, and (2) an intermittent contraction (6 s contraction, 4 s relaxation) at 50% of MVC force. MVCs were performed before and after the fatiguing contractions. RESULTS The endurance time of the women for the sustained contraction (1068 150 s) was longer than the men (720 111 s), despite a similar decline of MVC force after the fatiguing contraction (36 4% vs 38 2%). Similarly, the endurance time of the women for the intermittent contraction (1210 316 s) was longer than for men (378 41 s). Four pairs of men and women (n = 8) were matched for MVC force within 5% (265 14 N vs 260 14 N, respectively). The endurance time of the women (1176 254 s) for the sustained contraction was longer compared with men (762 133 s), despite a similar decrease in MVC force after the fatiguing contraction (36 4% vs 39 1%). Furthermore, the endurance time of the women (1170 498 s) for the intermittent contraction was longer than for men (351 39 s). Therefore, the difference in endurance time of men and women matched for strength was greater when blood flow was less disrupted (70% difference for the intermittent contraction) compared with when the blood flow was more occluded (35% difference for the sustained contraction). CONCLUSIONS The longer endurance time of women is due to factors other than those related to differences in muscle strength. Supported by an ACSM Research Endowment grant awarded to SKH and NIH NS43275 grant awarded to RME.