Role of the Ground Reaction Force Components in Balance Assessment during Squatting Exercise performed by the Wii Balance Board

The Nintendo Wii Balance Board (WBB) has been proposed as a valid low-cost device for the assessment of balance in many different motor tasks. However, the direct comparisons with the gold-standard for balance measure represented by the laboratory grade force plates (FP) showed fixed biases affecting both the center of pressure (CoP) computation and its related spatial parameters, which can be partially attributed to the negligence of horizontal ground reaction force (HGRF) components in WBB-CoP computation. Thus, this study aimed to quantify to what extent the absence of HGRF affects the errors between FP and WBB in CoP related parameters during the squatting movement, where significant HGRFs are involved. Results showed that the HGRF negligence affects errors between FP and WBB to a significantly different extent when squat exercise is performed with two different techniques, being higher when squatting does not reach the maximal depth (average value of 60% versus 40% for all the considered parameters). Outcomes of this study seem to indicate that the use of WBB could be preferable for motor task with a marked mono-axial dynamics and in particular for the squatting exercise performed with a high squatting depth.