Quantifying Dynamic Postural Stability Utilizing Center of Gravity Accelerations from Full-Body Kinematics

Abstract

Dynamic postural stability (DPS) indicates an individual's risk of losing balance during non-stationary tasks. Current approaches for assessing DPS are limited by their reliance on force-plates (FP) or predetermined tasks, as most were primarily designed for clinical assessments. This study developed a DPS index (DPSI) based on three-dimensional center of gravity accelerations (a COG ) derived from full-body kinematics (KM), providing an approach that is suitable for clinical and broader applications. Three participants performed repeated trials of a simulated roofing task on a wooden platform set at two slope conditions—flat (level) and 3/12 th pitch. The full-body kinematics were recorded by a 14-camera motion capture system and the ground reaction forces were measured via two FPs. The DPSI values from all participant trials were evaluated using the previously accepted FP-based and the proposed KM-based approaches. Our results displayed varied agreement between the two approaches across stability directions: medial/lateral (MLS), anterior/posterior (APS), vertical (VS), overall dynamic postural stability (DPS). The MLS measurements demonstrated the strongest agreement between the two approaches (relative difference ∼11%, r = 0.87 to 0.92). The proposed KM-based DPSI supports task-specific assessments and incorporates both average and maximum metrics.