Identification of human postural dynamics

Human postural dynamics was investigated for six healthy subjects using a force platform recording body sway induced by vibrators attached to the calf muscles. The model of body mechanics adopted was that of an inverted pendulum, the dynamics of postural control being assumed to be reflected in the stabilizing forces exerted on the platform by the feet as a result of complex muscular activity subject to state feedback of body sway and position. The approach to signal processing has been that of parametric identification of a transfer function representing the stabilized inverted pendulum. Posture control was quantified in three variables: swiftness, stiffness, and damping. It is shown that the identification fulfils ordinary statistical validation criteria, and it is conjectured that the state feedback parameters identified are suitable for use in assessing ability to maintain posture.