Correlation Between Center of Pressure Measures Driven from Wii Balance Board and Force Platform

The gold standard for postural stability evaluation is the force platform; which has multiple limitations such as high costs, not being portable and being difficult to implement. Simple balance training devices have been recently tried to take this role. The validity and reliability of such devices have been a major concern.
Twenty symptom-free university students volunteered to take part in this methodological study. The center of pressure, anterior-posterior displacement range and total path length were measured during static standing tasks under four conditions of eyes opened and closed with firm and foam support surface by Bertec force platform and Wii Balance Board. Intra-class correlation coefficient and standard error of measurement were used to assess relative and absolute reliability, respectively. The mean differences of the measurements of the two devices were compared to zero by one sample t-test to check the construct validity of the Wii Balance Board. Bland and Altman plots were also used for descriptive evaluation of the mean and the variability of measurement differences of the two devices. Regression analysis was used to check if there was any systematic bias between the mean values and the differences between the two devices.
All center of pressure measures from both devices showed statistically significant relative reliability (P 0.05). Regression analysis of the pooled mean scores and the measurement differences revealed no significant systematic bias between them (P > 0.05).
Both Bertec force platform and Wii Balance Board devices showed acceptable reliability. While the center of pressure driven variables measured by the two devices are comparable, there is a trend toward overestimation of these variables by the Wii Balance Board. The difference between the measurements of the two devices was found to be highly variable without any significant systematic bias.