Abstract
[Purpose] The purpose of this study was to investigate the effects of the position of an object, on postural adjustments during reaching movements in the sitting position. [Subjects] The subjects were 10 healthy volunteers. [Method] Subjects reached with the right hand for a plastic bottle (500 ml) placed in different positions. The object was placed straight ahead, 45° toward the right side, and 45° toward the left side. The movement was measured using a 3D motion analysis system and force plates. Three dimensional angles of the pelvis and the trunk were calculated, and the transitions of the center of mass and the center of pressure were investigated. [Result] The relative angle of the trunk to the pelvis showed a leftward rotation in all the tasks. The lateral inclination of the pelvis was leftward when reaching to the left side and straight ahead, but it was rightward when reaching to the right side. The center of mass moved in the direction of the target, but the center of pressure moved in the direction opposite to the target at the beginning of the movement. [Conclusion] These results suggested that the subjects reached for the object placed in different positions by changing postural adjustment.
