Validity of the Nintendo Wii Balance Board to assess weight bearing asymmetry during sit-to-stand and return-to-sit task

Abstract

Weight bearing asymmetry is common in patients with unilateral lower limb musculoskeletal pathologies. The Nintendo Wii Balance Board (WBB) has been suggested as a low-cost and widely-available tool to measure weight bearing asymmetry in a clinical environment; however no study has evaluated the validity of this tool during dynamic tasks. Therefore, the purpose of this study was to determine the concurrent validity of force measurements acquired from the WBB as compared to laboratory force plates. Thirty-five individuals before, or within 1 year of total joint arthroplasty performed a sit-to-stand and return-to-sit task in two conditions. First, subjects performed the task with both feet placed on a single WBB. Second, the task was repeated with each foot placed on an individual laboratory force plate. Peak vertical ground reaction force (VGRF) under each foot and the inter-limb symmetry ratio were calculated. Validity was examined using Intraclass Correlation Coefficients (ICC), regression analysis, 95% limits of agreement and Bland-Altman plots. Force plates and the WBB exhibited excellent agreement for all outcome measurements (ICC=0.83-0.99). Bland-Altman plots showed no obvious relationship between the difference and the mean for the peak VGRF, but there was a consistent trend in which VGRF on the unaffected side was lower and VGRF on the affected side was higher when using the WBB. However, these consistent biases can be adjusted for by utilizing regression equations that estimate the force plate values based on the WBB force. The WBB may serve as a valid, suitable, and low-cost alternative to expensive, laboratory force plates for measuring weight bearing asymmetry in clinical settings.

Keywords: Concurrent validity; Force plate; Sit-to-stand; Weight bearing asymmetry; Wii Balance Board.

Figure 1

Subjects performed the STS-RTS task while data from each foot was acquired from the force plates (A) or from the Wii Balance Board (B).

Figure 2

Example of vertical ground reaction force for both limbs throughout the sit to stand-return to sit (STS-RTS) task. Data were time-normalized to 100 points. The STS phase was defined as the first 25% of the task and RTS phase was defined as the last 25%.

Figure 3

Scatter plot illustrating the relationship between the VGRF measured using the Wii balance board (WBB) and force plates (FP) for the affected and unaffected sides (A,B and C,D), as well as for the Symmetry Ratio of VGRF (E and F) during Sit-to-Stand and Return-to-Sit phases.

Figure 4

Bland–Altman plots representing comparisons between the laboratory-grade force platform (FP) and the Wii Balance Board (WBB) during STS phase: (A) for the affected side; (B) for the unaffected side; and during RTS phase (C) for the affected side; (D) for the unaffected side. The mean line represents the mean difference between the devices, with the upper and lower lines representing the limits of agreement (two standard deviations).