Musculoskeletal Disorders and the Workplace Low Back and Upper Extremities (2001) / Chapter Skim
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Patterns of Evidence
Patterns of Evidence
Pages 351-363
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From page 351... ...
Furthermore, approximately 1 million people take time away from work each year to treat and recover from musculoskeletal pain and loss of function. For workers in their 50s and 60s, musculoskeletal disorders represent the most common cause of disability, and current projections suggest that these figures are on the rise.
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From page 352... ...
Concerns about whether the associations could be spurious have been considered and reviewed. Biological plausibility has been demonstrated in biomechanical and basic science studies, and further evidence to build causal inferences has been demonstrated by intervention studies that demonstrate reduction in the occurrence of musculoskeletal disorders following implementation of interventions.
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From page 353... ...
that have attempted to explain the relationship. For example, epidemiology typically searches for associations between external loading characteristics and reported outcomes, whereas the relationship between external loads and biomechanical loading is usually explored via biomechanical studies (adapted from National Research Council, l999b)
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From page 354... ...
For example, industries that tend to impose greater spinal loads on workers, such as patient handling and case distribution in warehouses or distribution centers, present significantly greater risk of low back pain and also greatly benefit from appropriate interventions. When individual physical work risk factors have been identified, and when combinations of these factors (e.g., load location and body postures)
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From page 355... ...
Thus, there is a need to quantify the magnitude of risk factors so that the degree of risk can be assessed. However, while work-related physical load, frequency of bending and twisting, physically heavy work, and whole-body vibration have been implicated in musculoskeletal disorders, evidence for static work postures has been less compelling.
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From page 356... ...
Biomechanical and Biological Evidence Our review of the biomechanical and basic biology literature provides a consistent explanation for the linkages established by the epidemiologic literature. Both the physical work factors pathway as well as the psychosocial pathways can be explained by the literature.
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From page 357... ...
Individual Factors Individual factors appear to mediate the biomechanical and biological pathway mechanisms described in Figure 10.1. Some part of the variance in response that has been described in the biomechanical and biological literature appears to be explained by individual host factors that can mediate loading response to external workplace factors as well as mediate tolerances to such loadings.
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From page 358... ...
There is also significant evidence that individual factors such as age, gender, and physical condition play important roles in mediating the response to work factors associated with biomechanical loading and with the tolerance levels for the individual. Thus, the literature also suggests that clear linkages appear in Figure 10.1 between individual factors and biomechanical loading and between individual factors and internal tolerances.
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From page 359... ...
There is good evidence that interventions are most effective when supported fully by workers and other key stakeholders. While the epidemiologic literature on psychosocial factors indicates that high levels of job stress and perceived job demands in particular were consistently related to the occurrence of upper extremity symptoms and disorders, few studies have investigated the effects of interventions directed at psychosocial risk factors in workers with these symptoms or disorders.
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From page 360... ...
Individual Factors Individual factors also mediate biological pathways for upper extremity disorders, especially for carpal tunnel syndrome. Nerve function declines with age and other factors (e.g., pregnancy and body mass index)
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From page 361... ...
The intervention literature supports the efficacy of tool and workstation design changes, job rotation, and other interventions that directly address these risk factors. Thus, while the upper extremity literature is less developed than the literature on low back pain, an analogous set of themes emerges, lending further support to the model presented in Figure 10.1.
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From page 362... ...
The epidemiologic literature that specifically quantifies heavy lifting shows that risk of injury is greatest when loads are lifted from low heights, when the distance of the load from the body is great, and when the torso assumes a flexed, asymmetric posture. Thus, risk estimates significantly increase when work risk factors can be classified with greater precision.
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From page 363... ...
Finally, a recent intervention study has demonstrated that alternative keyboards that reduce nonneutral wrist postures can mediate hand pain in patients with carpal tunnel syndrome. In conclusion, a clear and strong pattern of evidence emerges after considering the epidemiologic, biomechanical, basic science, and intervention literature collectively.
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