Adaptation of postural control while standing on a narrow unfixed base of support.

The purpose of this study was to investigate the adaptation with practice of postural control while standing on a rocker board. Thirteen healthy young adults participated. The participants were asked to stand in a sagittal plane on a rocker board with a semicircular base as steadily as possible for as long as they could. With practice, the duration of maintaining postural balance increased significantly and postural stability improved (P<0.05). Furthermore, the distances between center of pressure and the projection of center of mass decreased (P<0.05), although joint motion of the lower extremities did not change (P>0.05). This observation would be the consequence of a highly redundant human locomotor system. With practice, the central nervous system was able to shift the center of pressure position close to the accurate center of mass position.