Validity and reliability of the Nintendo Wii Fit Stillness score for assessment of standing balance

Background/objective
Standing balance has become an important clinical measure in patient populations who are at risk of falls or have osteoarthritis. With custom-written software, the Wii Balance Board (WBB) has been shown to be a valid and reliable force platform that can be used to assess standing balance. However, no studies to date have assessed the use of the more readily available Wii Stillness Score (WSS) as a measure of balance.

Methods
Twenty-four individuals without lower limb pathology performed a combination of unilateral and double leg standing balance tests with eyes open or closed on two separate occasions. At each session, data from the WBB were acquired on a laptop computer running custom software and then by Wii-Fit software on a Wii console. The reliability of the WSS was determined by assessing reproducibility, while the validity of the WSS was determined by comparing the results of the WSS to that of the custom-written software.

Results
We found that the WSS exhibited excellent intra and inter device reliability in three out of four stances tested. The Bland-Altman plots also showed good concurrent validity for the three analysed stances. However, there remain significant limitations with the use of the WSS such as its rigid thirty-second time parameter and single score result.

Conclusion
The readily available WBB may be a used as a portable and inexpensive device to assess standing balance with custom written software. However, with the current limitations of the WSS, we would discourage its use as a clinical measure of balance.