Recurrence quantification analysis of gait in normal and hypovestibular subjects

The study of postural control processes during locomotion may provide useful outcome measures of stability for people with unilateral vestibular hypofunction (UVH). Since nonlinear analysis techniques can characterize complex behaviour of a system, this may highlight mechanisms underlying dynamic stability in locomotion, although only few efforts have been made. In particular, there have been no studies that use recurrence quantification analysis (RQA), which can be applied even to short and non-stationary data. The purpose of this study was to develop a new method for walking balance assessment measuring the complexity of head, trunk and pelvis three-dimensional accelerations and angular velocities during normal overground locomotion by means of RQA in normal subjects and UVH patients. The results showed differential effect of upper body parts on pattern regularity, with better head than pelvis stabilization in both groups of subjects. The RQA outputs such as percent determinism and recurrence were nevertheless significantly lower in the UVH group for all measures, suggesting that body accelerations and angular velocities, although not significantly different in amplitude, were more chaotic in patients. The observed lower regularity of upper body movements in UVH is consistent with an important role of the vestibular system in controlling dynamic stability during walking. The findings suggest that RQA can be used as a quantitative tool to assess walking performance and rehabilitation outcome in patients with different balance disorders.