Different responses of skeletal muscle following sprint training in men and women.

Six male and ten female physically active students performed 30-s sprint training on a cycle ergometer three times a week for 4 weeks, to investigate the training responses of skeletal muscle and to evaluate possible sex differences in this respect. Three repeated sprint tests with a 20-min rest in between were performed and muscle biopsies from the vastus lateralis muscle were taken before and after the training period. Mean power (average of sprint I-III) and type IIB cross-sectional fibre area increased only in the women (7% and 25% respectively) following sprint training, resulting in a decreased sex difference. There was an increase in total lactate dehydrogenase (LD) activity following sprint training in both sexes, although the levels were lower in the women both before and after training. Glycogen content increased and the activity of LD iso-enzyme 1 decreased in the women, but not in men. It was hypothesised that both the smaller areas of type II fibres and lower activity of LD generally seen in women may be due in part to less frequent activation of type II fibres in women than in men. If this were the case, the women should respond to sprint training (a type of training that activates type II fibres) to a relatively greater extent than men. That the observed increase in type IIB fibre area in response to sprint training was greater in the women than in men supported the hypothesis of the study. However, the results for LD activity, which showed a similar response in the men and the women, did not support the hypothesis.