Metabolic and morphological profile in skeletal muscle of healthy boys and girls.

It was hypothesized that the typical adult pattern of higher glycolytic capacity in skeletal muscle of males compared to females is not observed in children and that fiber cross-sectional area (CSA) is a determinant of glycolytic capacity in children. Biopsies were performed in vastus lateralis in 9-12 years-old healthy boys and girls (N = 27). Fiber types were classified by myofibrillar ATPase staining and CSA was measured using planimetry.

Muscle fiber size in healthy children and adults in relation to sex and fiber types.

Background: In adult males, cross-sectional area (CSA) for type II muscle fibers is generally larger than for type I fibers. In this cross-sectional study the aim was to compare sex-related CSAs of various muscle fiber types during childhood-to-adulthood transition.

Methods: Percutaneous biopsy samples were obtained from vastus lateralis in 10-y-old children (10 males and 5 females) and in young adults (9 males and 7 females).

High proportion of type I fibres in thigh muscle of young dancers.

A previous study showed that adult female dancers have a high percentage 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 percentage of type I fibres or develop a high percentage of type I fibres as a consequence of dance training. Furthermore, the muscle fibre composition of male dancers has not previously been studied.