Cross Teager-Kaiser operator and Lempel-Ziv Index for the assessment of human posturographic data

In this study Cross Teager-Kaiser (CTK) operator was employed to combine the two stabilogram components recorded during static posturography to generate a new time-series that describes the interaction among them. Then, such interaction was measured through a complexity index as Lemepel-Ziv. The method proposed would overcome some limitations that classical posturographic data analysis encounters in underlining differences among groups of subjects. This aspect is of great interest in the assessment of pathologies that affect the nervous system and its balance control strategies. The discriminative capability of the proposed method was evaluated through two assessments: the first aimed to highlight differences between young and elderly subjects; the second, more challenging, required to highlight differences between diabetic patients without neuropathy and diabetic patients with asymptomatic neuropathy. Wilcoxon-Mann-Whitney tests revealed that CTK combined with Lempel-Ziv index significantly differentiate the groups in the two assessments.