Evaluation of lower back and lower limb kinetics while lifting a baby dummy in squatting, kneeling and standing postures

Musculoskeletal disorders affect childcare workers at the lower back and the lower limbs. Childcare professionals lift children while adopting standing, kneeling and squatting postures. The risks associated with lifting from standing postures have been extensively evaluated, but evidence remains insufficient regarding the adoption of kneeling or squatting postures. This study aimed to estimate peak intersegmental moments at the L5/S1, hips and knee joints during a lifting activity in these three postures. This biomechanical evaluation was conducted under controlled laboratory conditions using two baby dummies of 2.7 kg and 10 kg. Joint kinetics was assessed using tri-dimensional video data and ground reaction forces. Results suggest that both lifting posture and dummy's load impact peak intersegmental magnitudes in all the joints. Lifting from a standing posture using the 10 kg baby dummy presented the highest peak intersegmental moments at the L5/S1 and the hip joints, with associated magnitudes of 228 Nm and 131 Nm respectively. These magnitudes decreases around 20% in squatting and 40% in kneeling postures. In contrast, the solicitations at the knee joint were higher in squatting (75 Nm) and kneeling (92 Nm) postures. These orders of magnitude were comparable to those found in the literature using classical loads of equal or greater mass, likely due to the postural exigence related to the type of load (a baby dummy) and grip (under the armpits). However, considering the work specificities in a nursery, the current recommendations for manual material handling cannot be directly followed for childcare workers. • Lifting posture and baby dummy's mass affect peak intersegmental moment. • Peak L5/S1 moment oscillates 200 Nm in standing posture using a 10 kg baby dummy. • Peak intersegmental moments seem comparable for child and classic manual handling. • Current lifting recommendations cannot be directly followed for child manual handling.