Influence of gender on post-tetanic potentiation in human dorsiflexors

Twitch contractions of the ankle dorsiflexors were evoked before and after 7 s of tetanic stimulation at 100 Hz in young women and men. Torque decreas ed more in men (18%) than in women (12%) during the tetanus. There was no g ender difference in twitch peak torque potentiation over the 5-min post-tet anus. Potentiation was 42% (women) and 45% (men) at 5 s post-tetanus, and s till present at 5 min (women 24%, men 25%). The immediate (5 s) shortening of twitch rise time was similar in women (14%) and men (13%), but during th e 5-min men's rise time came to exceed whereas women's only approached pret etanus values (e.g., +9% vs. -1% at 5 min). The immediate decrease in half- relaxation time was also similar in women (24%) and men (22%); however, wom en's but not men's values remained less than pretetanus values for most of the 5-min period. Twitch rate of torque development increased similarly (75 %) in women and men at 5 s, with no gender difference over 5 min. Tn contra st, rate of torque relaxation increased significantly only in men. Rate of torque development normalized to peak torque was similar in women and men p retetanus and increased similarly 5 s post-tetanus, but women had greater v alues through most of the 5-min post-tetanus. Normalized rate of torque rel axation was similar in women and men and not affected by tetanus. In the do rsiflexor muscles, young women and men show a similar amount and pattern of twitch force potentiation, but there are gender differences in time-relate d twitch contractile properties in the first 5 min after tetanus.