Theoretical issues in understanding work-related musculoskeletal disorders causation

Keywords:

This special issue of Theoretical Issues in Ergonomic Science is devoted to helping explain the causation of work-related musculoskeletal disorders (WMSD's) through empirical and conceptual papers that focus on current theoretical topics. Recent debate on the causation of WMSD's concerns the nature, extent and quality of evidence to delineate specific causative factors and to develop effective interventions. In addition, the roles of the multiplicity of factors that may contribute to WMSD's causation is not well defined. The papers offer a variety of perspectives including biomechanical considerations, psychosocial contributions and macro-ergonomic (work organization) issues.

The first paper, by Swanson and Sauter (2005) examines 1 year of data from a longitudinal study of keyboard improvements to test their ecological model of musculoskeletal disorders in office work (Sauter and Swanson 1996). Analysis of the data from the first year shows significant relationships for keyboard condition and musculoskeletal symptoms, keyboard condition and work organization and work organization and stress. On the other hand, several pathways do not show significant results, including the relationships between work organization and musculoskeletal symptoms and stress and musculoskeletal symptoms. This incongruity in the relationships illustrates the very complex nature of WMSD's causation.

In the second paper, Sommerich and Hughes (2005) review evidence linking working conditions and disorders of the rotator cuff tendons. They discuss the anatomy of the rotator cuff to explain factors that make the rotator cuff tendons vulnerable to injury. Based on their review, the authors develop several theoretical issues that need to be examined in order to further the understanding of shoulder biomechanics. The factors include additional study of the effect of ischemia-reperfusion on tendons and the effect of arm posture on tendon perfusion (independent of external loading). Sommerich and Hughes also call for the development of biomechanical models to estimate tendon compression during work and the inclusion of anatomic factors in the analysis of epidemiological data. A main thrust of the paper is a discussion of and call for the use of more specific methods of exposure assessment to better understand the aetiology of rotator cuff tendon disorders.

In the third paper, by Carayon et al. (2005), the role of psychosocial work factors in a work organization intervention designed to reduce work-related musculoskeletal disorders is examined. A particular work organization factor of interest in this study is teamwork, because, as the authors point out, both the process and content of many work organization interventions rely on teamwork. The authors use structural equation modelling to test the theoretical perspective that the teamwork characteristics of open group process and group cohesiveness are important predictors of stress and musculoskeletal discomfort. The authors conclude that it is essential to incorporate an array of work organization and psychosocial factors in models of musculoskeletal discomfort.

In the fourth paper, Faucett presents a theoretical model of work-related musculoskeletal disorder causation that emphasizes the role of management systems and the work environment as key sources of strain. These in turn influence the development of work-related musculoskeletal disorders. The model is a modification of other models that Faucett (2005) reviewed linking psychosocial factors and work-related musculoskeletal disorders. The new model takes advantage of theories of acute injury causation as well as sociotechnical systems and macro-ergonomics. The author concludes with a discussion of methodological considerations, including the use of qualitative data to improve the capture of psychological and social factors at work.

In the final paper, Karsh (2005) reviews, compares and contrasts nine theories of work-related musculoskeletal disorder causation and then presents a composite model that depicted the 34 potential pathways of WMSD's causation suggested by the nine individual models. This composite model illustrates the complexity and multi-factorial nature of the aetiology of work-related musculoskeletal disorders. Karsh (2005) goes on to explain the theoretical and methodological implications of the composite model for ergonomic intervention research.

Taken together, the five papers in this special issue raise theoretical and methodological arguments that will hopefully facilitate new research into WMSD causation. While the complexity of the problem is certain, theoretical advancements are needed to continue to move the field closer to an understanding of WMSDs causation and how to improve the design of work.