Time-varying characteristics of postural sway differ between balance impaired and unimpaired populations

To study potential time-varying dynamics of postural sway as measured via center-of-pressure (COP), the authors applied time-frequency analysis to COP data from ten vestibularly impaired subjects and thirteen unimpaired controls, during quiet stance and in response to visual perturbation. This analysis revealed that: (1) the spectral characteristics of the COP change over time; (2) there are time-dependent and frequency-dependent differences in the COP between impaired and unimpaired populations during visual perturbation; and (3) there is no difference in the COP during quiet stance (eyes open) between impaired and unimpaired populations for the parameters investigated. A novel finding of this research is that controls appear to adapt to constant frequency visual perturbation, while vestibularly impaired subjects do not