The aim of the present study was to examine the concentric and eccentric isokinetic moment of knee extensors in 108 boys aged 6 to 12 years and in 15 young adults. Participants performed isokinetic concentric and eccentric knee extensions at different angular velocities, 45°, 90° and 180°·s
$^{-1}$
. The Ancova designs, using lean mass as covariate, revealed a significant age effect. Post hoc Scheffe test revealed higher moment scores for adults compared to children. Statistical differences between children were observed every two years. Eccentric moments were higher than concentric moments at corresponding velocities. Concentric moments decreased with increasing velocity whereas eccentric moments did not change significantly. Boys were found to achieve almost 40% concentric and eccentric moment of young adults at the age of 12 years. The higher annual increase of both concentric and eccentric moment was observed at 7 years of age.
The present data indicate a gradual and concurrent increase of isokinetic concentric and eccentric moment with age from 6 to 12 years of age suggesting probably a concurrent maturation of contractile and elastic components of the muscle during childhood.
