Wearable-only estimation of L5-S1 joint moments during lifting: A CEINMS-based validation

Abstract

Abstract This study aimed to evaluate the use of wearable sensors to estimate L5-S1 flexion moments during symmetric lifting tasks by integrating inertial motion capture (IMC), surface electromyography (sEMG), and the calibrated EMG-informed neuromusculoskeletal (CEINMS) framework. Eight participants performed stoop and squat lifting at four load levels while gold-standard optoelectronic motion capture, ground reaction forces, inertial measurement units (IMUs), and sEMG were recorded. IMC-based inverse dynamics showed excellent agreement with OMC (ρ = 0.83–0.96; ICC > 0.91), with mean errors around 2–3 Nm. CEINMS moments calibrated using wearable data exhibited strong reliability and captured the expected load-dependent increases in lumbar moments, although peak values during heavy lifting were systematically underestimated. IMC consistently underestimated L5-S1 flexion angles by 2°, likely contributing to the reduced peak moment estimates. Overall, findings support the feasibility of a wearables-only approach for ergonomic risk assessment. Future work should focus on improving lumbo-sacral flexion angle estimation from IMUs, potentially through multi-sensor lumbar configurations.