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


METHODS
Experimental, cross-sectional.


METHODS
Laboratorial experiment.


METHODS
Thirty healthy volunteers.


METHODS
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.
Faculty of Health and Social Sciences, Bournemouth University, Royal London House, Christchurch Road, Bournemouth, Dorset, BH1 3LT, UK. Electronic address: jwilliams@bournemouth.ac.uk.
Jonathan M
JM
Williams
Faculty of Health and Social Sciences, Bournemouth University, Royal London House, Christchurch Road, Bournemouth, Dorset, BH1 3LT, UK.
Christopher
C
Dorey
Faculty of Health and Social Sciences, Bournemouth University, Royal London House, Christchurch Road, Bournemouth, Dorset, BH1 3LT, UK.
Suzannah
S
Clark
Faculty of Health and Social Sciences, Bournemouth University, Royal London House, Christchurch Road, Bournemouth, Dorset, BH1 3LT, UK.
Carol
C
Clark
D061725:Accelerometry; D000328:Adult; D003430:Cross-Sectional Studies; D005260:Female; D005500:Follow-Up Studies; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D004856:Postural Balance / Q000502:physiology*; D015203:Reproducibility of Results; D012445:Sacrococcygeal Region / Q000502:physiology*; D013647:Task Performance and Analysis; D013997:Time Factors
Accelerometer; Balance; Minimal detectable change; Reliability