The purpose of this study was to examine the effect of decision making under a light stimulus on movement during a change of direction (COD). Twelve male soccer players performed 2 types of lightbased backward agility test (BAT): normal condition and pre-planned condition (BAT-PP). Their motions were videotaped using 2 high-speed cameras operating at 300 Hz for three-dimensional motion analysis. The time, step parameter, and each kinematic variable were compared to determine the differences between the BAT and BATPP. The results showed that the times for 5–13 m and 0–13 m in the BAT were slower than those in the BAT-PP. The velocity of the center of gravity at the lowest point of the velocity in the BAT was lower than that in the BATPP. During the pre-COD phase, the body inward lean angle, shoulder rotation angle, and pelvis rotation angle were all smaller in the BAT than in the BAT-PP. At the COD foot contact, foot placement in the left-right direction was shorter and knee flexion was greater in the BAT than in the BAT-PP. Furthermore, hip flexion during the deceleration phase, and shoulder and pelvis rotation during the acceleration phase were larger in the BAT than in the BAT-PP. Overall, these results may indicate that players who performed the BAT were required to maintain a posture that allowed them to turn to the left or right until the presentation of the light stimulus; therefore, their bodies were upright, and their trunks were facing the direction of approach before COD. Moreover, the knee joint flexed with a short distance to the left of the COD foot placement, the velocity of the center of gravity decreased with hip flexion, and the trunk rotated significantly to a new direction in the BAT.
