The purpose of this study was to investigate kinematic changes at the baseball batting motion for inside, center and outside hitting points. Subjects were ten right-handed male skilled batters of a varsity baseball club. Nine hitting points were set according to the baseball rules: three heights (high, middle, low) and three courses (inside, center, outside) based on the subject's height and the width of a home plate. The subjects were requested to hit a ball on a batting tee randomly assigned one of the nine hitting points in each trial. Kinematic data were collected by using a Vicon 612 system with nine cameras operating at 120 Hz. Angular kinematics computed were joint angles of the right and left elbows, shoulders, ankles, knees and hips, and rotation angles of the shoulders and hips at the instant of events of batting.

In case of the outside hitting point, the rotation angle of the shoulders toward the opposite hitting direction at the instant of Toe-on was greater, and the rotation angle of the hips toward the hitting direction at the Swing start (SS) was smaller than those of the center point. The rotation angle of the shoulders and hips toward the hitting direction at the instant of Left upper arm parallel (LUP) to the hitting direction was smaller, and the left elbow extension was greater than those of the center point. The abduction of the left shoulder and the rotation angle of the shoulders and hips toward the hitting direction at the impact were smaller than those of the center point. In case of the inside hitting point, the rotation angle of the shoulders toward the opposite hitting direction at the instant of Toe-on was smaller than those of the center point. The rotation angle of the shoulders toward the hitting direction, and the extension of the left ankle at instant of LUP was greater than those of the center point. The rotation angle of the shoulders and hips toward the hitting direction, and the extension of the left ankle and knee at the impact were greater than those of the center point.

These results indicated that to hit the ball at the inside and outside hitting points effectively a batter should first adjust the rotation of the shoulders and hips prior to the swinging down the bat with the upper limbs toward the hitting points.

The objective of the present study was to investigate kinematically as well as kinetically the mechanism of the speed-accuracy trade-off in a side-foot soccer kick. Eight experienced male soccer players and eight inexperienced players participated in the experiment. They were instructed to perform five grounder side-foot kicks under two conditions. In one condition, they were emphasized on accuracy rather than speed. In an other condition, they were emphasized on speed rather than accuracy. The resultant performance (i.e. ball speed and absolute error against the target line) was recorded. The joint torques and joint angles of the kicking leg were also determined based on the three-dimensional kinematic data acquired using a motion capture system. The present results suggested that the degree of the speed-accuracy trade-off effect was different depending on the skill level. The inexperienced players significantly lost their accuracy by emphasizing on ball speed. In contrast, the experienced players could keep their good accuracy even by emphasizing on ball speed because of their good impact skill. The mean ball speed of the experienced players was significantly faster than that of the inexperienced players regardless of speed-or-accuracy emphasis. This seems to be because skilled soccer players can use the hip-flexion torque more efficiently than unskilled players. In conclusion, skilled soccer players may emphasize ball speed when they kick a placed ball with the medial aspect of the foot under certain situations such as a penalty kick.