Development of a novel link-segment model for estimating lower back loading in paramedics

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Galbraith, Peter Alexander Wetherall
paramedics , low back , ergonomics , compression , link-segment modeling , biomechanics
Work conducted as part of this thesis evaluated the lifting techniques of paramedics using a novel link-segment model that was validated against a commercially available software package, 3D Static Strength Prediction Program (3DSSPP). Twenty-five paramedics visited the Biomechanics Lab at Queen’s University to participate in testing sessions mimicking the daily lifting and carrying tasks performed by paramedics on the job. Participants were outfitted with the Xsens Motion Tracking System and asked to lift and carry bags ranging from 5-20kg. Output from the Xsens system was used in a 3D-inverse dynamic model to estimate loading at the L5/S1 joint. The compressive and shear force estimates at this joint are of particular interest given their correlation with low back pain and injury. Across all conditions the greatest compressive forces were seen during bag pickup and bag release. Additionally, reaching forward 50 cm at pickup increased peak spinal compressive loads by nearly 300N and 500N for a 5kg and 10kg handbag respectively. Not surprisingly, at bag release greater trunk lean values were correlated with higher compressive force estimates. Single-shoulder backpack carries showed similar loading characteristics when compared to double-shoulder backpack carries. Shear force estimates remained well below acceptable levels across all conditions. Based on paramedic feedback, a supplementary testing session was performed with a single participant to evaluate multi-bag carries and stair climbing. The results of this testing session showed that loading was reduced at pickup and release when the load was distributed across two bags. This research led to the development of four recommendations that have been presented to the Association of Municipal Emergency Medical Services of Ontario. 1. Paramedics should not lift single bags or a combination of bags that exceed 20kg. 2. Prior to lifting, bags should be located as close to the paramedic as possible. 3. When placing bags on the ground and when picking bags up off of the ground, paramedics should use a squat lift technique to prevent forward and side bending. 4. When multiple bags are carried the load should be evenly distributed within bags and across sides of the body.
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