Accuracy of force and center of pressure measures of the Wii Balance Board

Abstract

The Nintendo Wii Balance Board (WBB) is increasingly used as an inexpensive force plate for assessment of postural control; however, no documentation of force and COP accuracy and reliability is publicly available. Therefore, we performed a standard measurement uncertainty analysis on 3 lightly and 6 heavily used WBBs to provide future users with information about the repeatability and accuracy of the WBB force and COP measurements. Across WBBs, we found the total uncertainty of force measurements to be within ± 9.1N, and of COP location within ± 4.1mm. However, repeatability of a single measurement within a board was better (4.5 N, 1.5mm), suggesting that the WBB is best used for relative measures using the same device, rather than absolute measurement across devices. Internally stored calibration values were comparable to those determined experimentally. Further, heavy wear did not significantly degrade performance. In combination with prior evaluation of WBB performance and published standards for measuring human balance, our study provides necessary information to evaluate the use of the WBB for analysis of human balance control. We suggest the WBB may be useful for low-resolution measurements, but should not be considered as a replacement for laboratory-grade force plates.

Keywords: Balance; Calibration; Force plate; Postural sway; Wii Balance Board.

Figure 1

WBB coordinate system and force transducers. A) The top surface of the WBB is shown with the coordinates used for computing the COP, sensor locations and the abbreviated protocol testing locations. B) Foot-pegs housing force sensors are found under each of the four corners of the board. C) The force sensor consists of a metal beam and strain gauge that acts as an uni-axial force transducer.

Figure 2

Custom weight application device. A) A custom weight-applicator consisting of a metal pole and 7/16” acorn nut was built to apply concentrated point loads. B) Calibrated masses were attached to the weight-applicator and the tip of the applicator was placed on the WBB at a desired location.