Reliability of an inexpensive and portable dynamic weight bearing asymmetry assessment system incorporating dual Nintendo Wii Balance Boards

Weight bearing asymmetry (WBA) during dynamic tasks is prevalent in a variety of clinical populations. However, accurate measurement has previously been out of reach of the clinician due to the costly equipment and technical expertise required. The aim of this study was to assess the test-retest reliability of WBA data obtained using an inexpensive and simple to use dual force plate system incorporating unmodified Nintendo Wii Balance Boards (NWBB) and customized software. A secondary outcome measure, individual limb COP path velocity, which represents the postural sway under each limb was also examined. Twenty-three participants performed squats both with and without visual WBA feedback on two separate occasions. Weight-bearing asymmetry as a percentage of body mass and individual limb center of pressure (COP) path velocity were recorded during these trials, with intraclass correlation coefficient (ICC_2,1) analysis performed to assess test-retest reliability. This system provided reliable values for both outcome measures when performed with and without real-time visual feedback of WBA (ICC_2,1 range = 0.75-0.91). In conclusion, recording WBA and COP path velocity data using NWBB is reliable. Given that tens of millions of NWBB have been sold worldwide, and that reprogramming them for clinical purposes is within the reach of most software developers, similar systems may soon become commonplace in the clinical setting.