To analyze walking turns, the influence the hip joint external rotation angle of the stepping limb in the standing position has on electromyographic activities of the upper and lower gluteus maximus muscle fibers was examined. The subjects were 10 healthy males with a mean age of 24.2. The standing position was defined as the position in which subjects stepped forward from a standing position. The hip joint external rotation angle of the starting position was changed, and the electromyographic activities of the upper and lower gluteus maximus muscle fibers were measured at each angle. The integrated electromyographic relative value of the upper gluteus maximus fiber significantly increased with the increase of the hip joint external rotation angle. The integrated electromyographic relative value of the lower gluteus maximus fiber also showed a tendency to increase. It is our opinion that the upper and lower gluteus maximus muscle fibers participate in the maintenance of the extension and external rotation of the support side hip through the actions of hip extension and external rotation. In addition, the support side hip performs adduction with increase in the angle of hip external rotation, indicating that the upper gluteus maximus fiber increases hip abduction to brake it.
