The within-day and between-day reliability of using sacral accelerations to quantify balance performance.
OBJECTIVES
To investigate the between-day and within-day reliability of a sacral mounted accelerometer to quantify balance performance and different balance metrics.


DESIGN
Experimental, cross-sectional.


SETTING
Laboratorial experiment.


PARTICIPANTS
Thirty healthy volunteers.


MAIN OUTCOME MEASURES
Balance tasks were double leg stance, tandem stance and single leg stance with eyes open and closed. Performance was measured by converting accelerations into path length (PL, length of the sway trace), jerk (jerkiness of sway trace) and root mean square (RMS) of the accelerations.


RESULTS
Within-day ICC for PL were excellent (mean 0.78 95%CI 0.68-0.89), with Jerk and RMS demonstrating means of 0.60 and 0.47, respectively. The mean percentage minimal detectable change (MDC) within-day were small for PL (mean 6.7%, 95%CI 5.3-8.1). Between-day ICC were good for PL (mean 0.61, 95%CI 0.50-0.71), but more varied for Jerk and RMS. The mean percentage MDC was small for PL (mean 6.1%, 95%CI 5.0-7.2). No significant differences were determined for measurements between-days for any metric or task. PL had the highest discriminatory value between the 8 tasks.


CONCLUSIONS
The sacral mounted accelerometer reliably measured balance performance within- and between-days. The PL is the recommended metric as it was the most reliable, most discriminatory and most sensitive to change.
['Williams|Jonathan M|JM|', 'Dorey|Christopher|C|', 'Clark|Suzannah|S|', 'Clark|Carol|C|']
D061725:Accelerometry D000328:Adult D003430:Cross-Sectional Studies D005260:Female D005500:Follow-Up Studies D064368:Healthy Volunteers D006801:Humans D008297:Male D004856:Postural Balance D015203:Reproducibility of Results D012445:Sacrococcygeal Region D013647:Task Performance and Analysis D013997:Time Factors
Reliability Balance Accelerometer Minimal detectable change