Age-related differences in kinematics and kinetics of sprinting in young female.

This study aimed to investigate the age-related differences in sprinting performance, kinematic and kinetic variables in girls aged between 7.0 to 15.3 years. Step-to-step spatiotemporal variables and ground reaction impulses during sprinting were collected in 94 Japanese girls across a 50 m in-ground force plate. From the results, a difference in rate of development in sprinting performance in girls over 12.7 years compared with younger girls (YG) was observed. The older girls (OG) became slightly slower each year (-0.09 m/s/year) compared to the YG (0.24 m/s/year) who increased their running speed. Moreover, height increased by 6.3 cm/year in YG and only 3.6 cm/year in OG, while step length during the maximal speed phase increased by 0.07 m/year in YG and plateaued in OG (0.01 m/year). Propulsive impulse during the initial acceleration phase was the only kinetic variable to differ in rate of development between the age groups with an increase of 0.024 Ns/year in the YG compared to -0.010 Ns/year in OG. The development of sprinting ability in Japanese girls was more rapid before age 12.7 years. The difference in rate of development in sprinting ability can be primarily attributed to greater growth rates in YG, contributing to increases in the propulsive impulse during the initial acceleration phase and step length during the maximal speed phase. The limited gains in step length and the propulsive impulse in OG may reflect their reduced growth rate in height and the fact that increases in fat mass with maturation impaired relative force production. This article is protected by copyright. All rights reserved.