Introduction: Many methods exist for evaluating ergonomic risk factors for LBP at workplace, including biomechanical, physiological and psycho-physical methods. Digital Human Modeling (DHM) as a tool based on computer for ergonomic evaluation that Because having advantages such as saving time and costs in assessment and actively evaluation of ergonomic solutions in the digital environment.Aim of this study was evaluation occupational causes of LBP with the use of digital human modeling.

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Method and Materials: This study was a case quasi-experimental study in the engine assembly of the car manufacturing industry was conducted. First, The characteristics of job and risk factors for low back pain In all workstations were documented, then workstations with high risk of low back disorders were selected. Finally, a workstation for simulating and evaluating in the human digital modeling softwares, which includes 3DSSPP and Catia were selected. A total 22 posture of the lifting and lowering moment of the three tasks of workstation selected for simulation. After evaluation in the digital environment, the risk areas identified and solutions were presented.

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Results: The results showed that compressive and shear forces on the L5/S1 disc increased with increase of anthropometric dimensions and Horizontal distance from the body and decrease of height Lowering the site, and the percentage of people capable to perform a task in joint, decreased with increase of anthropometric dimensions. Ligament strain in postures with sever bending trunk were more increasing. RULA scores increased with the Unsuitable conditions of back and arms. High risk areas, were mainly related to the low height of pallets in lifting and lowering and high Horizontal distance from the body.

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Conclusion: According to The results of this study, Biomechanical Causes for LBP, including anthropometric characteristics (height and weight), Horizontal distance of object to the body, height of lifting and lowering location and trunk bending and torsion. This study showed that DHM is an effective tool in the evaluation of job tasks and workplace design, that can be identified risk area in each task and to achieve the ideal design. Using DHM can be implement Desired solution in a virtual environment and With the re-evaluation, Be sure of having effective solutions in the real environment.