Postural stability measures: what to measure and for how long.

This paper assesses the repeatability of force plate postural stability measurements. The common parameters were investigated for five test durations, two vision conditions, and two stance conditions. All parameters were found to be reliable measures. Optimum test retest reliability was obtained at 20-s and 30-s trial periods. Centre of pressure measures increased with increased test duration while ground reaction forces and velocity decrease slightly. RELEVANCE:--The results indicate that measures of centre of pressure excursion and ground reaction forces can differentiate between various mechanical and sensory conditions and thus are clinically useful for detecting and quantifying both mechanical and sensorimotor postural deficiencies. It is also demonstrated that the test duration is important in the reliability and validity of stability measures.