抄録
This study compared the overarm throwing motion of skilled elementary school children with standard motion models in order to obtain suggestions for teaching overarm throwing. The subjects were 93 children from the second, fourth, and sixth grades of elementary school who were asked to throw a softball with maximal effort. Their throwing motions were videotaped with three high-speed cameras for 3-D motion analysis. Seven boys and seven girls were selected from each grade as good throwers based on their throwing distance. The standard motion model proposed by Ae et al. (2007) was established from the coordinate data for the good throwers of each grade. The primary variables computed were the release height, velocity, and angle of the ball, the joint angles of the upper and lower limb joints, and the segment angles of the trunk.
The findings obtained were as follows.
1) For skilled boys, the throwing distance and ball velocity increased significantly with increasing school grade, and the throwing distance and ball velocity were significantly related in all grades.
2) Skilled fourth and sixth grade boys greatly extended the flexed right knee joint in the striding phase and the right hip joint in the throwing phase. The range of motion of the rotation, forward-backward leaning of the trunk, and extension angle of the right elbow joint at ball release for sixth graders exceeded those of participants of other grades.
3) For skilled girls, the throwing distance and ball velocity increased significantly with increasing school grade, and there were significant relationships between the throwing distance and the ball velocity in fourth and sixth graders, and between the throwing distance and the release angle in fourth graders.
4) Skilled fourth and sixth grade girls significantly abducted the right hip joint and leaned the trunk rightward. The horizontal abduction angle and external-internal rotation angle of the right shoulder of sixth graders in the throwing phase exceeded those of the students in other grades.
These results indicate that the range of motion of the legs and trunk increased with increasing school grade and was a dominant factor in skilled boys, and that fast external-internal rotation of the shoulder and large right hip abduction were characteristic of skilled girls.
