Biomechanical study of the relationship between anthropometry and forces applied on the lumbar vertebrae during welding

Musculoskeletal disorders are predominant causes of workers, disabilities and reducing productivity in industrial countries. Studies should one of the jobs that may cause musculoskeletal disorders, is welding. To investigate the causes of these disorders, this study attempts to find relationships between workplace ergonomics, human anthropometry and the amount of force and torque acting on the lumbar vertebrae of welders.
In this study, two modeling and analysis methods in CATIA V5R20 software and reverse dynamic calculations, were used to assess biomechanical characteristics of 10 manikins with different anthropometric dimensions in 2 different welding positions. Also by using of occupational health and safety standards in software, the motor position of manikins limbs were judged.
Inverse dynamics calculations and CATIA software showed that by increasing the stature of American workers about 13%, the torque and force acting on the L4-L5 vertebrae increase approximately 45-47%. Also, by increasing the length of the upper and lower body segments, the percentage of workers who are not capable of welding, increased. In addition, Comparison between sitting and standing welding showed in sitting welding position, the force acting on the vertebrae is 26-28% more than standing position.
The results of this study compared with international standards such as NIOSH, indicate that by increasing the length of the upper and lower body segments in welders, the force and torque acting on the lumbar vertebrae increased and because of more force and torque in sitting than standing welding position, perils threaten the low-lying levels welders.