The effect of sports training on the age-related changes of body composition and isokinetic peak torque in knee extensors of junior speed skaters.

To elucidate the effect of sports training on age-related changes of body composition and isokinetic peak torque (IPT) in knee extensors, junior speed skaters were tested in comparison with relatively sedentary age-matched controls. Subjects consisted of 132 male and 71 female junior speed skaters (SSs; aged 10-18 years). Two-hundred and thirty-six males and 265 females between the ages of 10 to 18 in the same geographic area were also tested as controls (Cs). Lean Body Mass (LBM) and relative body fat (%) were estimated from skinfolds, using the equations for preadolescent boys and girls. An isokinetic dynamometer (Cybex II) was used to measure IPT (Nm) produced at angular velocities corresponding to 0, 30, 180, 300 deg.sec-1 during maximal knee extensions. SSs were heavier in body weight and LBM from age 13 for males and from age 16 for females than the Cs, and there were significant differences in LBM between SSs and Cs after age 16 regardless of sex. The female Cs showed a gradual increase in relative body fat (%) after age 14, however, such a trend was absent in female SSs. IPT increased in any angular velocity with age from 10-18 years in the male Cs, and from 10-15 years in the female Cs. On the other hand, male SSs tended to be stronger after age 13 and female SSs stronger after age 16. Significant differences between the two groups were obtained only at lower angular velocities from 16 years of age in both sexes.(ABSTRACT TRUNCATED AT 250 WORDS)