Reliability of Cop-Based Postural Sway Measures

Abstract

Measures of human sway during upright standing are frequently used as indirect measures of the postural control system. The objective of this study was to assess the reliability of several center-of-pressure-based sway measures. Test-retest reliability was determined both within-days (under different visual and surface conditions) and between-days (5 different days). Intraclass Correlation Coefficient (ICC), Standard Error of Measurement (SEM), Minimal Metrically Detectable Change (MMDC), and Coefficient of Variation (CV) were used as reliability indices. Mean velocity was found to be the most reliable measure among those evaluated. Overall, between-day reliability indices were better than within-day reliability. When subjects were standing on a compliant surface, several measures exhibited better reliability under ‘eyes open’ condition. These results can be useful in guiding the selection of postural sway measures and appropriate number of replications to improve sway assessment.

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