Muscle Fiber Characteristics in Female Dancers During an Active and an Inactive Period

Abstract

Muscle biopsies were taken from female dancers, aged 24 ± 2 years, first during an active period and then after 32 weeks of detraining. During the active period, the percentage of type I fibers was 63% ± 12%, and of the subgroups IIA, IIB, and IIC, 26% ± 9%, 8% ± 7%, and 3% ± 3%, respectively. There was no significant change due to detraining either in the proportion of type I fibers or in the type II subgroups. During the active period, the cross-sectional area of the type I fibers was 3798 ± 586 µm². The areas of the subgroups IIA, IIB, and IIC were 3394 ± 858, 2497 ± 530, and 3296 ± 638 µm², respectively. After the detraining period, the area of the type I fibers had increased significantly (P < 0.05). The areas of the types IIA, IIB, and IIC tended to be increased although not significantly. It is suggested that the comparatively high percentage of type I fibers, which was found in the active dancers, is the result of selection rather than of training, while the small fiber areas seem to be due to training.

muscle fiber types - muscle fiber areas - woman - dance - physical training - detraining