| Title: | Test–retest reliability of postural sway measures using a portable low-cost force plate in healthy adults |
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| Authors: | ID Vindiš, Miha (Author)
ID Kozinc, Žiga (Author)
ID Nedović, Nenad (Author) |
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| Files: |  https://onlinelibrary.wiley.com/doi/10.1002/pri.70270
https://doi.org/10.1002/pri.70270
 RAZ_Vindis_Miha_2026.pdf (550,07 KB)
MD5: 3819BC0F3D6D93E845133D217DB76FCD
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| Language: | English |
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| Work type: | Article |
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| Typology: | 1.01 - Original Scientific Article |
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| Organization: | FVZ - Faculty of Health Sciences
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| Abstract: | Background and Purpose Center of pressure (CoP) metrics derived from force plates are widely used to quantify postural control, but laboratory-grade systems limit routine clinical and field implementation. Portable low-cost force plates could enable physiotherapists to monitor balance longitudinally, provided that their measurements are sufficiently reliable and clinically interpretable. This study addresses a gap in the literature by systematically comparing the test–retest reliability of CoP outcomes across bipedal and single-leg stance conditions using a portable low-cost force plate, providing device-specific and task-specific validation data relevant to clinical and field-based implementation. Methods This test–retest reliability study included 27 healthy young adults who completed two laboratory sessions 7–10 days apart. In each session, participants performed three 30-s trials of bipedal quiet stance and three 30-s trials of single-leg stance on each leg barefoot with standardized arm position and visual fixation. Mean values across repetitions were analyzed. Relative reliability was assessed using two-way mixed-effects ICC for absolute agreement (3,1), with 95% confidence intervals. Absolute reliability was quantified using typical error (TE) and coefficient of variation (CV). Paired t-tests evaluated systematic between-session differences. Results Across all outcomes, single-leg stance demonstrated substantially higher inter-session reliability compared to bipedal stance. Measures of total CoP displacement and velocity during single-leg stance exhibited good to excellent reliability (ICC = 0.85–0.90) and low absolute error (CV ≈ 8%), with direction-specific displacements showing similarly consistent results (ICC = 0.83–0.90; CV generally < 10%). In contrast, the CoP ellipse area and standard deviation measures were considerably less stable (ICC = 0.57–0.79) and displayed markedly higher variability (CV ≈ 16%–23%). The contrast was even more pronounced in the bipedal stance, where reliability was poor to moderate across all parameters (ICC = 0.39–0.65), with the ellipse area exhibiting excessive variability (CV > 60%). Notably, no systematic between-session differences were observed for most outcomes, further supporting the consistency of the measurements. Discussion In healthy young adults, single-leg stance provides more reliable CoP measures than bipedal quiet stance when using a portable low-cost force plate. Displacement- and velocity-based outcomes during single-leg stance appear most suitable for repeated assessments and monitoring. MDC95 values should be interpreted strictly as measurement-error thresholds and not as indicators of clinical responsiveness or meaningful clinical change because responsiveness was not evaluated. |
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| Keywords: | balance, reliability, force plate |
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| Publication version: | Version of Record |
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| Publication date: | 02.07.2026 |
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| Year of publishing: | 2026 |
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| Number of pages: | str. 1-9 |
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| Numbering: | Vol. 31, iss. 3, [article no.] e70270 |
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| PID: | 20.500.12556/RUP-23287  |
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| UDC: | 612.76 |
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| ISSN on article: | 1471-2865 |
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| DOI: | 10.1002/pri.70270 |
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| COBISS.SI-ID: | 284112387 |
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| Publication date in RUP: | 08.07.2026 |
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| Views: | 24 |
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| Downloads: | 0 |
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