ABSTRACT
The purpose of this study was to clarify the differences in reaction time, stepping frequency and stepping endurance estimated by chronological age compared to skeletal age. The participants were 76 well-trained soccer players aged from 9.7 to 14.8 years old. Height and weight were measured before training. Their skeletal ages were evaluated by RUS score of TW II method. RUS score was calculated for skeletal age by Murata's method. Reaction time, stepping frequency and endurance were measured by Talent-Diagnose-System (Werthner Sports Consulting, KEG, Co, Ltd.) . For chronological age, height increased linearly from 9 to 14. Height estimated by skeletal age increased slowly from 8 to 10, then increased drastically between the ages of 10 to 15. Significant change was shown between the ages of 12 and 13 (p<0.01) . Complex reaction time (CRT) estimated from chronological age developed linearly from 9 to 14 years of age. However for skeletal age, CRT at 10 was slower than at 8 and 9 years of age. Then it developed significantly between the ages of 10 and 11 (p<0.05) . On the other hand, stepping frequency and endurance did not show as remarkable a change with increasing age as reaction time. The results of this present study indicate that in adolescent soccer players, there are some differences between skeletal age and chronological age in cross-sectional change of reaction time. Moreover, skeletal age did not affect the development of stepping frequency and endurance.