The role of physical capacity in the development of low back and neck/shoulder disorders in a working population
10 / 2003 - 05 / 2008
The load-tolerance model assumes that musculoskeletal disorders can be explained by an imbalance between load and tolerance (physical capacity), and this imbalance may result in localized musculoskeletal discomfort (LMD), which can ultimately cause musculoskeletal symptoms and disorders. Many studies have reported on the association between workload and musculoskeletal disorders, but the modifying role of physical capacity (muscle strength, endurance time and joint mobility) has only sporadically been taken into account. The main objective of this study is to investigate the role of physical capacity in the relationship between workload and low back and neck/shoulder pain. Secondly, changes in physical capacity over time will be investigated, and also the relationship between physical capacity and age and gender. Thirdly, the validity of the LMD score will be investigated. - METHODS. In this prospective cohort study, 1,789 workers recruited from 34 companies were monitored for 3 years. This longitudinal Study on Musculoskeletal disorders, Absenteeism, Stress and Health (SMASH) started in 1993 to investigate work-related risk factors for low back, neck, and shoulder pain. The baseline measurements included a comprehensive questionnaire, as well as sick leave registration, measurement of workload by video-recordings, a physical examination and the LMD score. The questionnaire contained questions on physical and psychosocial load at work and during leisure time, individual factors and musculoskeletal disorders. During the physical examination, physical capacity was measured by means of dynamic lifting power tests for back and arm muscles, sub-maximal endurance tests for back, neck and shoulder muscles, and mobility measurements for the back, neck and shoulders. The LMD score was calculated to obtain a rating (between 0 and 10) of the perceived feeling of discomfort (pain, fatigue, tremble, etc.) in any part of the body. Follow-up questionnaires were sent to the workers once each year, and at the end of the study physical capacity was measured again. Risk factors for neck and low back pain have already been investigated with SMASH data, but the effect of physical capacity on outcomes such as neck/shoulder pain and low back pain has not yet been taken into account. In this study, secondary analyses of physical capacity will be performed.