Assessment of Postural Sway Area in Single-Leg Balance: A Comparative Analysis of Center-of-Pressure Area Metrics with the Convex Hull approach

PURPOSE: Quantifying postural control using Center-of-Pressure (COP) data obtained from a force plate is commonly used in balance assessments, yet the sensitivity of various sway area metrics remains unclear. This study introduced the convex hull area as a novel metric and aimed to examine how four COP-based sway area measures–rectangular, 66% effective, 95% ellipse, and the convex hull area–respond to progressively restricted visual conditions during single-leg balance. We also aimed to identify how the convex hull area performed relative to traditional sway area metrics.METHODS: Forty healthy adults (20 males and 20 females) performed three 10-second single-leg balance trials on a force plate under progressively restricted visual conditions using stroboscopic goggles. Three traditional COP-based sway area parameters and the introduced convex hull area were used to quantify single-leg postural control. All participants completed the balance tests under six visual conditions.RESULTS: A two-way repeated measures ANOVA revealed a significant interaction between sway area parameters and visual conditions (F=5.90, <i>p</i><.001). The 95% ellipse area showed the highest sensitivity, followed by the convex hull, rectangular, and 66% effective area parameters across different visual conditions. The 95% ellipse and convex hull area produced similar results and were significantly different from the rectangular and 66% effective area (<i>p</i><.001).CONCLUSIONS: These findings suggest that the convex hull area is capable of detecting changes in postural control alongside the 95% ellipse area, performing comparably to traditional sway area metrics. Our results may contribute to the standardization of COP-based sway area metrics.