抄録
We aimed to examine the influence of the leg step on the throwing motion in male children by performing kinematic analysis. The subjects were 36 boys (average age: 4.37 ± 0.26 years). The subjects’ softball-throwing motion was filmed with high-speed video cameras and three-dimensional analysis was performed by using the DLT method. The young children were classified into the following 3 groups according to the step motion of the leg: (1) non-throwing arm side-step group (NTA, n=17), (2) throwing arm side-step group (TA, n=10), and (3) non-step group (NS, n=9). Our results showed that there was no significant difference in ball speed among the NTA (6.6±1.5m/s), TA (6.8±1.5m/s), and NS (5.4±1.3m/s) groups. Subjects in the NTA group showed a great range of rotation and higher rotating angular velocity of the shoulder and waist; however, they did not transfer the energy of the lower limbs to elbow extension angular velocity or ball speed. In contrast, subjects in the TA group showed excessive trunk twisting while throwing; however, they threw the ball with a substantial forward inclination of the trunk. These findings suggested that the step motion of the leg did not influence the ball speed in 3-year old children because the children’s movement patterns were still immature.
