Development and validation of a markerless method for low back intersegmental moment assessment in early childhood care

In early childhood care settings, the frequent adoption of awkward postures and repetitive manual material handling tasks are biomechanical risk factors for the development of musculoskeletal disorders. Estimating low back intersegmental moments under realistic conditions could help identify such risks. Since working conditions with children are hardly reproducible in laboratory settings, to enhance ecological validity, intersegmental moments should ideally be estimated directly in situ. This makes measurement particularly challenging, particularly in achieving a balance between unobtrusive instrumentation and acceptable accuracy. The aim of this study was to develop and evaluate a markerless method for estimating low back intersegmental moments in the context of early childcare work. In laboratory conditions, eight participants performed six manual material handling and sit-to-stand tasks, representative of real work situations, using two different baby dummies weighting 2.7 kg and 10 kg. The proposed method, only based on video recordings, was evaluated by comparison with a reference approach combining marker-based motion capture and force platforms. Mean absolute differences in L5/S1 joint moment estimation between both approaches were approximately 20 Nm, which is comparable to errors reported in the literature for methods that can be deployed in situ. By requiring no instrumentation or participant preparation, this method offers a practical solution for quantifying low back intersegmental moments in situ within early childhood care environment.