Inertial Sensor-Based Assessment of Postural Control During Modified Romberg Conditions: Normative Reference Metrics from Healthy Adults

Postural control relies on the integration of visual, vestibular, and somatosensory inputs under biomechanical constraints. Conventional Romberg testing provides limited quantitative insight, particularly regarding directional control and sensory dependence. Wearable inertial measurement units (IMUs) enable portable, multidimensional assessment of postural sway. Thirty healthy adults (15 females, 15 males) completed a modified Romberg protocol with systematic manipulation of stance (normal, tandem), visual condition (eyes open, eyes closed), and arm position (arms at sides, arms forward), including both left and right leading foot during tandem stance. Whole-body kinematics were recorded using a full-body IMU system comprising 17 wireless sensors. Center-of-mass (CoM) trajectories were derived from a 23-segment biomechanical model, and linear, spatial, and nonlinear sway metrics were computed. Statistical analyses were conducted using repeated-measures ANOVA, with significance set at p < 0.05. Visual deprivation significantly increased sway path length, mean sway velocity, and sway area across all stance conditions (p < 0.001). Tandem stance elicited greater mediolateral sway than normal stance (p < 0.001). Romberg ratios exceeded unity for all metrics and were significantly higher in tandem stance (p < 0.01). Arm position effects were negligible in normal stance but showed significant Vision × Arm interactions during tandem stance (p < 0.05). Leading foot position had no significant main effects. Combining a modified Romberg protocol with full-body IMU-based CoM analysis enables sensitive characterization of sensory dependence and directional postural control. Tandem stance with visual deprivation increases mediolateral postural demands under reduced base-of-support conditions, providing a more challenging context for evaluating directional postural control.