Motion analysis of the lower extremities generating the rotation of the trunk around its long axis in some movements.

在网球、棒球或高尔夫中，主干绕其长轴的旋转对于提高球拍、球棒、球杆和球的速度非常重要。本研究的目的是利用摄影技术和力量平台，对日本网球和棒球领域的大学生运动员以及三名职业高尔夫球运动员和两名业余高尔夫球运动员进行实验研究，以阐明其产生旋转的机制。以200fps的标称胶片速度拍摄网球运动员的单手或双手反手上旋击球、棒球运动员的发球台击球和高尔夫球手使用发球手的发球台击球，同时测量每只脚在测力台上的作用力，并用逆动力学方法确定击球运动中双脚关节周围的扭矩。然后，确定了在三种击球动作中，后腿的髋关节伸肌和前腿的髋内收肌对骨盆旋转有贡献的髋关节扭矩分量。前腿的髋屈肌也对发球区击球时的旋转起到了作用。在网球反手击球和高尔夫发球台击球中，髋屈肌对旋转没有贡献，因为网球运动员必须伸展前腿的髋关节才能将球拍向上摆动，以获得顶部旋转球，高尔夫球手必须伸展关节，使手臂在击球前立即用力将击球手拉到旋转中心。

The rotation of the trunk around its long axis is important for making racket or bat or club and ball speeds large in tennis or baseball or golf. The purpose of this study was to clarify the mechanisms of the lower extremities to generate the rotation using cinematography and force platforms.Japanese college athletes in the fields of tennis and baseball, and three professional and two amateur golf players with low handicap participated in this experiment. Single-handed or doublehanded backhand top-spin strokes of the tennis players, tee batting of the baseball players and tee shots of the golfers using a driver were filmed with a nominal film speed of 200 fps, and the force which each foot acted on the force platform was measured simultaneously.The torques around the joints of the lower extremities during the hitting motions were determined using an inverse dynamics. Then, hip torque components which contributed to the rotation of the pelvis around its superior-inferior axis was determined.The hip extensors of the rear-leg and the hip adductors of the fore-leg contributed to the pelvis rotation in the three hitting motions. The hip flexors of the fore-leg also contributed to the rotation in the tee batting. The hip flexors did not contributed to the rotation in the tennis backhand strokes and golf tee shots because that the tennis players had to extend their hip joint of the fore-leg to swing the racket upward for a top spin ball and that the golfers had to extend the joint to have the arms pulling the driver hard to its rotational center immediately before ball impact.