Objective: The purpose of this study was to investigate the validity and reliability of a customized smartphone application (CSA) for postural sway (PS) assessment.

Methods: This validity and reliability study evaluated static balance by measuring PS in 29 healthy volunteers (15 women, 14 men, mean age 28 ± 5.11). Assessments included synchronized data collection using 3 systems: the CSA, a force plate, and the clinical modified balance error scoring system (mBESS). The experimental procedure included three 40-seconds long repetitions in 3 positions. Outcome measures included pathway and 95% ellipse area. Statistical analysis compared the developed application to both the force plate and the mBESS to test its validation and analyzed repeatability of the 3 experimental measurements.

Results: Good to strong correlations were found between the CSA and the force plate in double and tandem stance (pathway r = 0.81-0.91), and moderate to high reliability was found for the CSA (0.66-0.75) and for the force plate (0.69-0.77) pathway measurements. The similarity in reliability results of the 2 devices and the high correlation both support the validity of the CSA. Furthermore, a high correlation was demonstrated between the CSA and the mBESS (r = 0.80), higher than the force plate and the mBESS.

Conclusion: The developed CSA was found valid and reliable in healthy young adults, and further research is needed to recommend it for clinical balance assessments. The CSA could therefore be considered for PS assessment in the clinical field.

Author keywords: Postural Balance; Reliability and Validity; Biomechanics

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