Interaction of biomechanical and morphological factors on shoulder workload in industrial paint work

It is known that work-related musculoskeletal disorders are caused by multifactor operations of various risk factors. Among these, the association of these risk factors with pain symptoms and work-related musculoskeletal disorders have been reported in many studies in all typical manufacturing settings (Bernard, 1997). This study focuses on the automobile industry.

Twenty-nine paint area production workers of an automobile industry plant took part (age 37.7+/-8.2 years; seniority 6.9+/-6.2 years). Musculoskeletal morbidity was assessed through a questionnaire-administered interview and a clinical exam. Each workplace exposure was assessed by the observational rapid upper limb assessment method. The quantification of the workload on shoulders and wrists during the actual work task accomplishment was obtained through surface EMG.

Biomechanical exposure varied significantly between pain symptomatic and asymptomatic workers. It was the only estimator that could predict the risk of occurrence of musculoskeletal symptoms. Multifactor linear analysis showed that some linear and combined anthropometric characteristics could be associated to a higher workload on the shoulders and upper limbs.

The rigid external working conditions for employees with different morphologic characteristics, combined with demanding force application associated with the adoption of awkward postures for long and continuous periods of work time, impose constraints in accomplishment of the paint tasks. Additionally our results suggest that the same work task could present different musculoskeletal mechanical load for people with different anthropometrics.