Test-Retest Reliability of Postural Sway Measures Using a Portable Low-Cost Force Plate in Healthy Adults.
Miha Vindiš, Žiga Kozinc, Nenad Nedović
This portable balance plate tracks single-leg sway reliably in healthy young adults — displacement and velocity scores hold steady across sessions.
Two-legged standing scores are too noisy to track change, and none of this has been tested in patients.
Key findings
1Single-leg stance produced consistently higher inter-session reliability than bipedal stance across all centre-of-pressure parameters.
2In single-leg stance, total CoP displacement and displacement velocity were the most stable measures, with ICC values between 0.85 and 0.90 and coefficients of variation of approximately 7%–9%.
3Bipedal stance showed poor to moderate reliability across all parameters, with ICC values ranging from 0.39 to 0.65, and the ellipse area was the worst performer (ICC 0.42, CV exceeding 60%).
Still to come
How it was doneWhat they foundWhat it means for PTs
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What it does not show
Only 27 participants, 21 of whom were men, all healthy young adults — no older adults, no patients, no balance-impaired individuals. No simultaneous recording from a laboratory-grade force plate, so there is no criterion validity or cross-device agreement data. All data processing (filtering, CoP reconstruction, velocity estimation) was done inside the manufacturer's proprietary software; the investigators could not independently verify the calculations. Tasks were static quiet standing only; no dynamic or functional balance challenges were included. No a priori power analysis was performed. Trial averaging (mean of three repetitions) was applied before reliability calculations, which may inflate the estimates. The mechanism by which single-leg stance improves reliability (higher signal-to-noise ratio) was not directly tested.
Declared interests
Funded by the Slovenian Research Agency (KINSPO programme, P5-0443). The funder played no role in study design, data collection, or manuscript preparation. Authors declare no conflicts of interest.
The easy way to misread this
Do not read these reliability figures as validation of the plate for clinical use in patients — the study tested only 27 healthy young adults, included no comparison to a laboratory-grade standard, and the authors state plainly that the results should not be generalised to rehabilitation or neurological populations. The MDC values are measurement-error thresholds, not benchmarks for meaningful clinical improvement.
Summarised by AI from the full paper, without a clinician reviewing it. Check it against the source before it changes what you do. Read it on PubMed →