優れた投能力を持つ女子児童の投動作の特徴：全国小学生陸上競技交流大会ソフトボール投げ出場者の動作分析から

抄録

The purpose of this study was to investigate the characteristics of the overarm throwing motion of skilled elementary schoolgirls, and to obtain suggestions for teaching throwing motion to elementary school pupils. The subjects were the top ten and bottom ten girls who were selected on the basis of their rank in the ball-throwing event at a national athletic meeting for elementary school pupils. The girls were also videotaped by two high-speed cameras for three-dimensional DLT analysis. Three-dimensional coordinate data smoothed by a Butterworth digital lter were used to calculate ball velocity and joint kinematics, and to obtain a standard motion for each group, as reported by Ae et al. (2007).
The initial velocity of the balls thrown by the top 10 girls was signicantly greater than that of the bottom 10 girls. There were signicant differences between the two groups in the elbow joint angle, internal/external rotation angle and horizontal adduction/abduction angle of the shoulder joint, and lateral lean angle of the torso at the touchdown, knee joint angle of the step leg at the release, and the range of motion of the knee joint angle of the driving leg. The major characteristics of the throwing motion of the top 10 girls were 1) release with the elbow joint extended, 2) a great range of backward twist of the torso and back swing of the right arm, and 3) quick internal rotation of the right shoulder joint before release. In the second phase after touchdown of the step foot, the girls turned the driving knee inward and forced the body forward, while the bottom 10 girls tended to extend the driving knee and move the body slightly upward compared with the top 10 girls.