The effect of aging on vertical postural control during the forward and backward shift of the center of pressure.
Preventing fall-related injuries is becoming a priority as the world population ages. This study's purpose was to examine the effect of aging on vertical postural control in the community-dwelling elderly. Thirty-six elderly individuals and twenty-two healthy young adults were asked to shift their centers of pressure (COPs) as far as possible while standing. The COP position, angle of each lower leg joint, and postural muscle activities were measured using a force plate, three-dimensional motion analyzer, and electromyogram, respectively. The vertical position of the center of mass (COM) was also measured to assess the change in vertical postural control. The backward COP shift in the elderly group was significantly smaller than that in the young group, and both the forward and backward COM shifts were significantly smaller in elders relative to those in youths. The COM position in the elderly group during the backward COP shift was also significantly lower than that in the young group. Knee and ankle joint movements differed between the two groups during the backward COP shift. Factor analysis indicated that dorsal and ventral muscle groups were involved in the COP shift. Specifically, the relationship between the biceps femoris muscle and the voluntary COP shift was reinforced in the elderly group. These findings suggest that the vertical postural strategy changes in the elderly during the backward COP shift.