Experimental validation of a torso-mounted inertial sensor system for human balance and motion assessment

Abstract

Wearable inertial measurement units (IMUs) provide a mobile and cost-effective alternative to laboratory motion analysis and are increasingly used in Industry 4.0 for ergonomic assessment, workload evaluation, and biomimetic modelling in human–robot interaction. However, the validity of IMU-based body centre of mass (CoM) estimation depends on sensor configuration. This pilot technical validation study evaluates agreement between an upper-torso- and upper-extremities mounted IMU and a pedobarographic platform during quasi-static standing with controlled torso rotation. Lateral and sagittal CoM displacements were compared using RMSE, correlation coefficient, area-under-curve (AUC) difference, and frequency-domain analysis. Higher agreement was observed in the left–right direction (RMSE = 1.514 cm, r = 0.851), suggesting that the partial IMU setup may be suitable for monitoring lateral torso sway relevant to balance and postural load under quasi-static conditions. In the forward–backward direction, agreement was low (r = 0.488) due to the absence of lower-limb motion capture. Results demonstrate both the potential and limitations of partial IMU setups for ergonomic monitoring and task optimization in industrial environments.