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The objective of this study was to realistically include the effect of facet loading in an EMG-assisted lumbar biomechanical model. Most biomechanical models lack detailed facet geometry, the inclusion of cartilage, and fail to model the full lumbar spine. Several new facet-specific components were added to an EMGassisted biomechanical model, including realistic geometry and facet-specific contact algorithms. These algorithms defined nonlinear contact between each lumbar spine facet. Subject-specific data were applied to the model for assessment. As expected, resultant disc loads were generally lower in the model with facets. This information improves our understanding of how loads are distributed in the spine, and it can lead to a better understanding of causal pathways. If we understand those pathways, we then realise how to design better ergonomic interventions.

The purpose of this study was to quantify how musculoskeletal disorder exposure risk changes in an auto assembly task as a function of car body rotation. Twelve subjects participated in the study. There were three car body angles including 1) zero or standard, 2) forty-five degrees and 3) ninety degrees from horizontal. Musculoskeletal exposure included spine loads, spine posture, shoulder posture, neck posture and wrist posture, as well as normalized electromyography of the shoulder and neck. The results showed that musculoskeletal disorder exposure risk decreased as the car was rotated to forty-five degrees and further decreased as the car was rotated to ninety degrees. Thus, rotating the car body reduces musculoskeletal exposure which in turn may reduce the risk of musculoskeletal disorders. It should be noted that the results may vary with other assembly tasks.

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