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Introduction: Biomechanical quantitative evaluation of work activity in nurseries is challenging due to the presence of multiple individuals (professionals and children), furniture, and varied tasks. Caring for children up to 3 years old requires manual handling from postures like stooping, squatting, kneeling, and sitting. The evaluations conducted to date in nurseries were unable to evaluate manual handling activities in all these postures, though they are recognized as biomechanical risk factors. Current in-situ evaluations involve instrumenting professionals, which seems to impact their gestures. Given the significant incidence of musculoskeletal disorders linked to manual handling and postures, this study aims to assess the feasibility of quantifying trunk posture and moments in nurseries using video data.

Methods: Eight video cameras Sony RX0II recorded at 60 Hz work activities in a nursery over one day, covering playtime, nap preparation, and room tidying. Calibration was performed using a checkerboard in Theia3D (2023.1). Participants were not instrumented and they were asked to perform their work activities as usual. Manual handling activities, such as lifting, deposing, carrying and holding, were identified from video data using Kinovea (2023.1.1). Kinematics were assessed using Theia3D and considered valid if i) calculated at each frame throughout the activity and for all joints, and ii) if coherent in magnitude with the performed movement. Intersegmental moments at L5/S1 were assessed using the biorbd toolbox. Feasibility was evaluated from the number of handling activities analyzed, the postures and activities assessed, and the trunk inclination and L5/S1 intersegmental moments obtained.

Results: A total of 121 handling activities were identified for two childcare workers in 1.8 hours of videos: 76 presented invalid kinematics, 9 other involved handling a child, and 36 handling objects or loads considered negligible. Of the 45 valid activities, postures such as standing, sitting (on the floor or in chairs), kneeling, and squatting were assessable. Walking with a child in the arms showed trunk inclination and moments below 20° and 40 N.m, respectively. Child lifting and deposing involved trunk inclination over 60° and L5/S1 intersegmental moments up to 140 N.m.

Discussion: These magnitudes suggest that child lifting and deposing could be a biomechanical risk factor of musculoskeletal disorders, which is in agreement with current knowledge during childcare. Walking with a child appeared to be less exigent at the lower back.

Conclusion: These preliminary results suggested that it is feasible to use video data for quantitative evaluation of biomechanical risks factors during childcare in a nursery. The use of video data, when kinematics is valid, allows an evaluation without changing work activity and from all the postures commonly adopted by childcare professionals.