Subjective and Objective Measures to Assess Postural Instability: Their Linear Correlations and Abilities to Detect Effects of Work-related Factors

Abstract

The linear correlations between one subjective - perceived postural instability (PPI) and fifty-one objective postural instability measures were investigated, and their abilities in detecting the main and interaction effects of three work-related factors were compared. Results showed thirty-five objective measures had large correlations (|r| ≥ 0.5) with PPI. Center of pressure (COP) related measures had stronger abilities for detecting the factors’ effects than the other objective measures. Especially, ten of them, together with PPI, successfully detected (p < 0.05) both the main and interaction effects of all studied factors. High discriminating power, an overall high intra-class correlation coefficient and a small mean absolute difference between test-retest illustrated the PPI is reliable and sensitive for postural instability measuring. COP movement-related (velocity, acceleration, time to contact), and phase plane parameter, planar deviation in velocity, distance to the closest base of support boundary are recommended objective measures.