2003 Volume 30 Issue 1 Pages 1-7
The aim of this investigation was to clarify the effect of change in posture and motor coordination by repetition of the same task. Eleven healthy subjects with a mean age of 23.6 ± 2.6 years participated in this study. They were ordered to reach forward as a motor task. The sway area of the center of pressure (COP) and electromyography (EMG) of the lower extremity muscles were measured in the reaching position and the displacements of COP and body segment positions were measured. EMG was measured at M. Gluteus Maximus (GM). M. Semimembranosus (SM), M. Tibialis Anterior (TA) and M. Gastrocnemius (GC). The displacement of body segments was measured at position of the wrist, shoulder, hip and knee joint. The task was repeated 10 times, and results of the first and final trials were compared. In the reaching position in the first trial, the sway area of the COP increased. All muscles measured showed higher activity than at the starting position. The COP moved forward, but the position of the hip joint moved backward while reaching. In the final trial, the sway area of the COP decreased compared with the first trial. The only muscles that increased significantly at reaching position were SM and GC in the final trial. The distance that the COP moved increased, while the backward movement of hip positions became shorter than in the first trial. These results suggest that repetition of a reaching task may improve the stability of the posture by changing postural control strategy.
