2.4. Definition

Alignments on the three-dimensional space coordinates were calculated for the pelvis and thorax angles according to a define described previously [11,12]. The pitching direction (the direction towards the catcher) was regarded as the longitudinal axis of the coordinates, the line between the first base and the third base as the lateral axis, and the vertical line to the ground as the vertical axis. The mid-point between right and left anterior superior iliac spines of the pelvis was regarded as the center of the axis. Moreover, the line connecting the mid-point between right and left posterior superior iliac spines and the mid-point between right and left anterior superior iliac spines were considered as the longitudinal axis. Furthermore, the line connecting right and left anterior superior iliac spines as the lateral axis, and the vertical line to the plane consisting of the lateral and longitudinal axes as the vertical axis. In addition, in for thorax, the line connecting the mid-point between C7 and T10 and the mid-point between the clavicular notch and the xiphoid process was regarded as the longitudinal axis, the line connecting the mid-point between C7 and the clavicular notch and the mid-point between T10 and the xiphoid process as the vertical axis, and the vertical line to the plane consisting of the longitudinal and vertical axes as the lateral axis. The center of the axes in the thorax was regarded as the point 7 mm behind the radius of the infrared light reflective markers that were pasted along the longitudinal axis starting from the clavicular notch. The center of the axes in the thorax was regarded as the clavicular notch.