Skeletal muscle characteristics of racing reindeer (Rangifer tarandus).

Samples from the middle gluteal muscle of 3-7-year-old racing reindeer were taken before (7 reindeer) and at the end of the racing season (12 reindeer) for determination of fibre type composition, activities of citrate synthase (CS), 3-hydroxyacyl-CoA-dehydrogenase (HAD) and the glycogen content. Muscle samples were also taken from 7 female and 18 male reindeer of same age for histochemical determination of muscle fibre composition. During the racing season the fibre type composition remained unchanged as did the activities of CS and HAD. The high activities of CS and HAD together with the high intensity in the NADH-dehydrogenase stain indicate that the reindeer muscle has a high oxidative capacity. The glycogen content increased during the winter which can explain the increasing tendency in the transverse fibre area. The racing reindeer had a lower percentage of type I fibres and a higher percentage of type IIA fibres than the ordinary male reindeer. The differences in the fibre type composition suggest that the racing reindeer represent a selected reindeer population.