Dynamic Posturography: Perturbed equilibrium assessment on healthy adult subjects

Posturography is a fundamental tool to investigate the systems involved in the postural control either in static and in dynamic conditions. In the present paper we decided, by using sinusoidal perturbations of base support around the anteroposterior axis, to analyze the equilibrium parameters widely used in posture control studies - i.e. Compensatory Postural Adjustments (CPAs) and Anticipatory Postural Adjustments (APAs) - in the perspective of defining a range of equilibrium parameters for healthy adult subjects. Fourteen subjects (9 males and 5 females) with no experience of the experimental procedure participated to the experiments. Sine and step movements of the moving base were imposed through a 3-DOF (Degrees Of Freedom) robotic system and both standard and here proposed novel indices were calculated for the evaluation of equilibrium performance. The results suggest that the length of the Center Of Pressure (COP) trajectory is proportional to the frequency of the oscillations of the platform in the sine perturbation trials, while the range of motion of COP is not influenced. Moreover, we found the absence of asymmetries in the healthy subjects when they performed the session with step perturbations.