USE OF ‘TIME SPENT IN BALANCE CORRECTION’ AS A MEASURE OF BALANCE.

Abstract

Purpose/Hypothesis: Conventional measurement of postural sway from force plate technology has been derived from the standard deviation of the individual center of pressure locations relative to the average center of pressure location. When measuring static balance activities such as tandem stance, some data was occasionally lost if subjects took a step (i.e. used a step strategy) or otherwise changed body position during testing. The purposes of this study were to: 1) develop a measure of postural sway that incorporated these normal balance strategies and 2) examine the relationship of this new measure with conventional measurement. Number of Subjects: Fourteen women with a mean age of 26 years. Materials/ Methods: The subjects completed two trials each of two different static standing balance tasks while standing on a force plate with their eyes closed: 1) standing with feet together and 2) standing with feet together with a vibratory stimulus applied to the bilateral gastrocnemius muscles. A sliding, 10 ms time window was used to examine each 60 second trial. If the subject had more than a pre-specified change in any of the three dimensions of movement, “corrective activity”was recorded. The final measure was the percentage of time spent in balance correction (TSBC). Results: ANOVAs demonstrated that the new measure, TSBC, and conventional measurement both showed a significant difference between the vibration condition and the normal condition (p < 0.05).When the effect size of the balance tasks on each measure were examined, the strength of association between the balance tasks and the measure was greater for the TSBC measure (R2 =0.79) than for the conventional measure (R2 = 0.68). Conclusions: The TSBC measure demonstrated more sensitivity than conventional measurements in detecting the balance difference between two static standing balance tasks. Clinical Relevance: Therapists working clinically view balance strategies, such as stepping, as appropriate responses in a given environmental context. Researchers have seldom incorporated the appropriate use of balance strategies into their measurement of postural sway. The TSBC measure offers the advantage of incorporating a clinical perspective to bridge the gap between research and clinical views of balance.