Abstract
Few studies have used a longitudinal design approach to evaluate the development of isokinetic performance in children. The purpose of the present study was to evaluate isokinetic muscle performance in the same cohort of normal boys from pre-teen until late maturity (based on bone age assessments). Twelve healthy boys from a local soccer team were recruited. They were tested at six various occasions from pre-puberty until maturity. The mean age at inclusion was 9.8 (9.3–10.3) years. At each test anthropometric data(height, weight, chronological age and bone age) were collected. Isokinetic muscle function in knee flexion and extension was tested concentrically at 60 and 240°/sec. Bone age was generally retarded compared to chronological age; in average by -1.0 (-4.1.–1.7) years. There was a significant increase in absolute muscle performance values through the whole study period. When the values were normalized by body weight significant differences occurred only between test 3–4 and 4–5. This study indicates that a significant increase in muscle performance per se occurs in healthy boys during puberty, i.e. from the bone age of 12 until 17 years. Furthermore bone age does influence the development of isokinetic muscle performance but body weight is the normalizing factor that best explains the increase in performance.