Technical and Clinical Validation of a Portable Optical Fibre Balance Mat for Quantifying Postural Sway in Older Adults

Background: Early identification of balance impairments is critical for detecting the fall risk in older adults. Force plates are the standard for measuring postural sway, but are restricted in practice because they are cumbersome and expensive. The Balance Mat is a portable device that requires comprehensive validation against force plates and clinical benchmarks in older adult populations. Objective: The objective of this study was to evaluate the technical validity and clinical discriminative ability of the Balance Mat against a laboratory-grade force plate, clinical tests, and the fall history in an older adult cohort. Methods: Fifty-six community-dwelling older adults performed static balance assessments across six stance conditions. Postural sway data were recorded simultaneously using the Balance Mat and a force plate. The technical validity was assessed using Spearman’s rank correlation and intraclass correlation coefficients. Linear regression models were applied to calibrate the Balance Mat outputs against the force plate. The diagnostic accuracy for classifying the fall risk against the timed up and go test, the Falls Efficacy Scale-International, and the retrospective fall history was evaluated using an area-under-the-curve analysis. Results: The Balance Mat demonstrated strong associations with force plate measurements, particularly for the sway path/velocity, variance and Area95 (r>0.80). Following calibration, the absolute agreement for the sway path/velocity reached excellent levels (ICC=0.93) and good levels for Area95 and RMS (ICC>0.75), whereas the mean sway demonstrated a poor agreement and was excluded. For fall-risk classification, the calibrated Balance Mat achieved a fair accuracy for the retrospective fall history and a high Falls Efficacy Scale-International concern (area under the curve, 0.76-0.78), and a fair accuracy for the timed up and go thresholds (area under the curve, 0.70). Conclusions: The calibrated Balance Mat provided valid measurements of postural sway that aligned with the force plate parameters, particularly for the sway path/velocity and Area95. The within-stance agreement for the sway path/velocity ranged from ICC= 0.44 to 0.88, and the pooled value should not be interpreted as the uniform performance across all stance conditions. Given its fair diagnostic accuracy, the device is best utilised as a portable screening tool in combination with standard clinical assessments and the fall history rather than as a standalone diagnostic test.