Study of the accuracy of stance regulation

In order to find a rule underlying the control of stance we recorded the center of pressure intermittently every 29 ms, first with subjects standing still for 30 s and then during shifting the center of gravity along the margin of the supporting area for 30 s to detect any movement. Subjects were 5 adult volunteers. They were examined with eyes open and closed as well as standing on one leg, closed legs, and legs 15 cm apart. The distribution of cumulated densities of the center of pressure, in a 3-D drawing, formed a very simple graph, i.e., a tower on a circle. As the difficulty of stance increased, the circle was reduced and the height of tower lowered, independently of visual or supporting condition. Since easy and difficult stances could be simulated by small and large values of SD in a regular distribution, stance may yield action-oriented computation based on probability.