Slower fatigue and faster recovery of the adductor pollicis muscle in women matched for strength with men

In previous gender comparisons of muscle performance, men and women rarely have been closely matched, absolute force has not been equalized, and rates of fatigue and early recovery have not been determined. We compared adductor pollicis muscle performance at a similar absolute force development in healthy men and women (both n = 9) matched for adductor pollicis maximal voluntary contraction (MVC) force (132 ± 5 N for women and 136 ± 4 N for men, mean ± SE, P > 0.05). Subjects repeated static contractions at a target force of ≃ 50% of MVC force of rested muscle (68 ± 3 N or 51.9 ± 1.0% MVC for women and 72 ± 2 N or 53.0 ± 2.0% MVC for men, P > 0.05) for 5 s followed by 5 s rest until exhaustion, i.e. inability to maintain the target force for 5 s. MVC force was measured following each minute of exercise, at exhaustion, and after each minute for 3 min of passive recovery. For women compared with men: MVC force fell less after 1 min of exercise (to 93 ± 1% vs. 80 ± 3% of MVC force of rested muscle, respectively, P < 0.05); MVC force (N min^-1) fell ≃ 2-fold slower (P ± 0.05); and endurance time to exhaustion was nearly two times longer (14.7 ± 1.6 min vs. 7.9 ± 0.7 min, P < 0.05). After declining to a similar level of MVC force of rested muscle at exhaustion (56 ± 1% for women and 56 ± 3% for men), MVC force rose faster in women than in men (to 71 ± 2% vs. 65 ± 3% of MVC force of rested muscle, respectively; P ± 0.05) during the first minute of recovery. The findings are consistent with the hypothesis that slower adductor pollicis muscle fatigue in women is linked with differences between men and women both in impairment of force generating capacity, per se, and in rates of recovery between contractions.