Abstract
The purpose of this study was to elucidate techniques for kicking along various trajectories in direct free kicks from various point in soccer. The subjects were the four skilled soccer players belonging to a university soccer club. The subjects were required to hit each of 4 targets at various combinations of heights and positions in the goal (3.5 m left, and 3.5 m right from the center of goal aria; 1.2 m, and 2.2 m from the ground) behind a screen positioned 9.15 m in front of the kicker. The performances were recorded by six normal-speed video cameras. The behavior of the kicked ball was recorded by two normal-speed video cameras placed behind the kicker and two other normal-speed video cameras placed beside the kicker and analyzed using the three-dimensional direct linear transformation method. The fifth video camera was placed facing the kicker to capture variables related to ball rotation. The sixth video camera was placed beside the kicker to capture when the ball was kicked. The results were as follows: 1) In X-axis, initial direction of the ball just after being kicked is the most important parameter for every subjects and conditions to hit the target. 2) In Z-axis, not only initial direction of the ball just after being kicked but also other parameters about rotation are the important parameter for some subjects and conditions to hit the target.
