HIGH PROPORTION OF TYPE-I FIBERS IN THIGH MUSCLE OF YOUNG DANCERS

A previous study showed that adult female dancers have a high percenta ge of type I fibres in vastus lateralis. similar to that of endurance- trained female runners or female cross-country skiers. It is not known if dancers already at an early age are characterized by a high percen tage of type I fibres or develop a high percentage or type I fibres as a consequence of dance training. Furthermore. the muscle fibre compos ition of male dancers has not previously been studied. Therefore the a im of the study was to analyse skeletal muscle fibre characteristics i n 10-year-old and 20-year-old dancers of both sexes. Age-matched boys and girls whose physical activity was average for their age groups ser ved as controls. Muscle biopsies for histochemical analysis were obtai ned from vastus lateralis using the percutaneous needle technique. The major finding of the present study was that the vastus lateralis of y oung dancers of both sexes had a higher percentage of type I fibres th an that of controls. Moreover. the higher type I percentage was seen n ot only in 20 year olds, but also in 10 year olds, who had begun their dance training at a professional level only a few weeks earlier. No s ignificant difference in this respect was found between Female and mal e dancers. In conclusion. the muscle fibre type composition in young d ancers of both sexes differs from that of the average individual of th e same age and is characterized by a high percentage of type I fibres.