1. Validation of Postural Sway Measurements using Wii Balance Board
Zachary Meadea, Jenny A. Kenta, Nicholas Stergioua,b, Kota Z. Takahashia
Department of Biomechanics, University of Nebraska-Omaha, Omaha, NE 68182
University of Nebraska Medical Center, Omaha, NE 68198
INTRODUCTION
METHODS
Standing balance measurements can be useful in determining functional ability, risk of falling, and recovery after injury [1,2].
Previous studies have confirmed the accuracy of the magnitude of sway in the Wii Balance Board (WBB) when compared to laboratory grade force plates [2, 3].
No studies to date have analyzed validity of WBB in temporal structure of postural sway.
The purpose of this study is to validate postural sway measurements calculated from the WBB, specifically detrended fluctuation analysis.
Hypothesis: We hypothesize that postural sway measurements of the WBB will be within 5% from those of laboratory grade force plate.
The WBB is placed on top of the force plate for simultaneous data collection
3-min standing trials (Fig. 2):
Eyes-open
Eyes-closed
One-legged
These trials will be randomized.
Wii Balance Board
Laboratory Grade Force Plate
Figure 2: Trial setup for simultaneous data collection
DFA and RMS is calculated from center of pressure trajectories captured by two devices simultaneously:
Nintendo® Wii Balance Board (WBB)
Laboratory-grade strain-gage force plate (FP)
(OPTIMA, AMTI Inc., Watertown, Massachusetts, USA)
The Center of Pressure is extracted from both devices.
DETRENDED FLUCTUATION ANALYSIS (DFA)
RESULTS & DISCUSSION
Data is currently being collected.
Once analyzed this data may verify the temporal postural sway of the WBB.
Figure 1: Detrended Fluctuation Analysis.
DFA characterizes patterns of sway over a given time series. This allows us to see patterns in natural occurring phenomena that may otherwise have gone unnoticed.
Time series is integrated and divided into time lengths n (Fig.1a).
Then, Root mean squared deviation (F) from the local trend is calculated (Fig. 1b).
Lastly, fluctuation plotted against window length (n) in a log-log plot (Fig. 1c).
DFA is important because alterations to the α value within biological signals have been linked to disease and aging [4].
CONCLUSIONS
Data collection is now underway. This will determine whether consistency is maintained in measurements of postural sway patterns throughout a given sample size.
Once data is analyzed we will be able to make a proper inference of the accuracy of the temporal sway measurements collected by the WBB.
REFERENCES
ACKNOWLEDGEMENTS
1. Winter DA, et al. Med Prog Technol, 16, 31-51, 1990.
2. Hubbard B, et al. J Otolaryngol Head Neck Surg 11, 31-35, 2012.
3. Abujaber S, et al. Gait & Posture, 41, , 2015.
4. Peng CK. Chaos, 5, 82-87, 1995.
Team BLADE and the UNO Department of Biomechanics have been instrumental in the ongoing success of this study. This work was supported by the Center for Research in Human Movement Variability of the University of Nebraska at Omaha, NIH (P20GM109090), and NIH (R15HD086828).