Analysis of differences in manual material lifting behavior between healthy weight and underweight females

Manual material lifting is associated with risk factors that can lead to musculoskeletal disorders. Body mass index (BMI) plays a critical role in determining the health status of individuals and the burden on the musculoskeletal system. This study aims to compare the lifting behaviors of underweight and healthy weight female participants through the net reaction moment and g-force effects on the L5/S1 joint. For this purpose, participants are asked to perform two different types of manual material lifting actions: stooping and squatting. Joint movements are analyzed using IMU sensors and a 3D kinematic model and dynamic calculations are performed using the Newton-Euler method. Squatting lifting caused higher peak extension moments at the L5/S1 joint compared to stooping lifting. Underweight participants experienced lower moments during squat lifting than healthy weight participants. While there is no significant difference between subjects with healthy weight and subjects with underweight in the evaluations made with peak net reaction moments, a significant difference is revealed in the comparisons made on g-force, which is an evaluation criterion free of mass. This study revealed the critical role of BMI on manual material lifting biomechanics. Although underweight females have a mechanical advantage when manual material lifting, they may be less maneuverable due to imbalance, increasing their risk of injury, so ergonomic training and individualized lifting strategies should be developed.