found in the poultry processing and telecommunication industries, where interventions resulted in reductions in the total number of recordable repetitive trauma disorders (according to the criteria of the Occupational Safety and Health Administration [OSHA]), lost workdays, number of days of restricted activity, and employee turnover. In these latter examples, there is also some evidence that the interventions were cost beneficial for employers.

Further evidence for effective intervention is found in several well-designed studies that show that alternative hand tool designs result in improved hand and wrist posture, thereby minimizing the risk of musculoskeletal disorder. And there is some evidence that weight handling devices reduce the risk of musculoskeletal disorders (Smith et al., 1998).

Most of the industry-specific studies used multicomponent interventions (e.g., engineering controls, training, medical management, employee empowerment). Although these studies attempted to provide insights into the relative importance of each component, it is often not possible to identify those features of the overall intervention that are most critical in achieving the observed benefits.

Future Research

Although the research base contains valuable information and shows consistent patterns regarding the relationships between stressors and musculoskeletal disorders, additional research would provide a better understanding of the processes involved. Looking across the areas defined in the framework, there are five interrelated and fundamental issues that deserve additional attention by researchers:

  1. In all areas, additional research would shed light on the models and mechanisms that underlie the established relationships between causal factors and outcomes. For example, it is obvious that a tissue will fail when loaded above its ultimate strength. How tissue responds to repetitive loading, what triggers inflammatory responses, and how these are influenced by individual factors have not been explained in detail. A similar argument can be made for intervention studies, especially those that involve multiple components. Here, the literature shows that a "bundle" of actions can reduce the risk of musculoskeletal disorders and associated outcomes (e.g., sick days). What is less clear are the mechanisms by which changes to work procedures, equipment, environment, and organization, as well as to social and individual factors, produce the benefits.

  2. Along with a better understanding of the mechanisms that produce tissue failure and mechanisms that produce reductions in risks, the relationships between symptoms, injury reporting, impairment, and disability should be clarified, as well as how these relationships are influenced by individual, social, legal, and environmental factors. That is, there is a need to conduct more studies that consider multiple factors—workers generally are exposed to multiple factors—and there is likely to be significant interaction between factors.

  3. The literature identifies a range of procedures and equipment-related intervention strategies that can be effective. It would be helpful to know more about the relationships between incremental changes of the environmental load and incremental responses. Knowledge of these relationships could help to define more efficient and better targeted interventions.

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