Less regular postural sway is linked with age-related decline of postural control.

Age-related decline of the physiological functioning of the sensorimotor system negatively affects balance control. According to the hypothesis of reduced complexity with ageing and disease, lower functional complexity of the control system would induce center-of-pressure motion (CoP) of balance that is less complex (observed to be more regular). In contrast, regular CoP could also reflect optimal control from an intermittently controlled inverted pendulum perspective. Whether more regular CoP motion represents compromised control is debatable. We aimed to assess the relation between: i) age and CoP regularity; ii) postural sway estimated from unactuated inverted pendulum dynamics (using CoP) and regularity, to investigate the ‘source’ of CoP regularity. Age and regularity were negatively related. Regularity was positively related with longer unactuated inverted pendulum dynamics. Less regular CoP motion was associated with age-related decline of balance control possibly due to less optimal use of inverted pendulum dynamics.