Estrogen and gender do not affect fatigue resistance of extensor digitorumlongus muscle in rats

The effects of estrogen on skeletal muscle fatigue are controversial. To de termine the effects of estrogen and gender on rat extensor digitorum longus (EDL) muscle, we either injected 40 mu g beta-estradiol 3/benzoate.kg BW-1 to female rats or sham injected male or female rats for 14 days. Subsequen tly a 90 min fatigue protocol consisting of electrical stimulation at 10 Hz delivered in 500 ms trains was administered. Force was recorded for a 5 s period at the start of the protocol (0 min) and at 5 min intervals until co mpletion following 90 min of stimulation. After 90 min, EDL force generatio n at 10 Hz stimulation declined in all groups to between 50-60 % of initial values. However, no significant difference in fatigue rate or final 10 Hz stimulated force was seen between females administered estrogen, sham injec ted females or males. Hence, estrogen administration and gender did not sig nificantly affect EDL muscle fatigue in this model.