What are Work-Related Musculoskeletal Disorders (WMSDs)?

Although definitions vary, the general term "musculoskeletal disorders" describes the following:

Disorders of the muscles, nerves, tendons, ligaments, joints, cartilage, or spinal discs

Disorders that are not typically the result of any instantaneous or acute event (such as a slip, trip, or fall) but reflect a more gradual or chronic development (nevertheless, acute events such as slips and trips are very common causes of musculoskeletal problems such as low back pain)

Disorders diagnosed by a medical history, physical examination, or other medical tests that can range in severity from mild and intermittent to debilitating and chronic

Disorders with several distinct features (such as carpal tunnel syndrome) as well as disorders defined primarily by the location of the pain (i.e., low back pain)

The term "WMSDs" refers to (1) musculoskeletal disorders to which the work environment and the performance of work contribute significantly, or (2) musculoskeletal disorders that are made worse or longer lasting by work conditions. These workplace risk factors, along with personal characteristics (e.g., physical limitations or existing health problems) and societal factors, are thought to contribute to the development of WMSDs [Armstrong et al. 1993]. They also reduce worker productivity or cause worker dissatisfaction. Common examples are jobs requiring repetitive, forceful, or prolonged exertions of the hands; frequent or heavy lifting, pushing, pulling, or carrying of heavy objects; and prolonged awkward postures. Vibration and cold may add risk to these work conditions. Jobs or working conditions presenting multiple risk factors will have a higher probability of causing a musculoskeletal problem. The level of risk depends on the intensity, frequency, and duration of the exposure to these conditions and the individual s capacity to meet the force or other job demands that might be involved. These conditions are more correctly called "ergonomic risk factors for musculoskeletal disorders" rather than "ergonomic hazards" or "ergonomic problems." But like the term "safety hazard," these terms have popular acceptance.

Why are WMSDs a Problem?

Many reasons exist for considering WMSDs a problem, including the following:

WMSDs are among the most prevalent lost-time injuries and illnesses in almost every industry [Bureau of Labor Statistics 1995, 1996; National Safety Council 1995; Tanaka et al. 1995].

WMSDs, specifically those involving the back, are among the most costly occupational problems [National Safety Council 1995; Webster and Snook 1994; Guo et al. 1995; Frymoyer and Cats-Baril 1991].

Job activities that may cause WMSDs span diverse workplaces and job operations (see Table 1; see also Tray 1-A of the Toolbox).

WMSDs may cause a great deal of pain and suffering among afflicted workers.

WMSDs may decrease productivity and the quality of products and services. Workers experiencing aches and pains on the job may not be able to do quality work.

Because musculoskeletal disorders have been associated with non work activities (e.g., sports) and medical conditions (e.g., renal disease, rheumatoid arthritis), it is difficult to determine the proportion due solely to occupation. For example, in the general population, non occupational causes of low back pain are probably more common than workplace causes [Liira et al. 1996]. However, even in these cases, the musculoskeletal disorders may be aggravated by workplace factors.

What is Ergonomics?

Ergonomics is the science of fitting workplace conditions and job demands to the capabilities of the working population. Effective and successful "fits" assure high productivity, avoidance of illness and injury risks, and increased satisfaction among the workforce. Although the scope of ergonomics is much broader, the term in this primer refers to assessing those work-related factors that may pose a risk of musculoskeletal disorders and recommendations to alleviate them.

What is the Purpose of this Primer?

Many organizations have published primers and manuals describing programs and techniques to control ergonomic hazards [National Safety Council 1988; Canadian Center for Occupational Health and Safety 1988; Putz-Anderson 1988; UAW-GM Center for Health and Safety 1990; Oxenburgh 1991; American Meat Institute and ErgoTech, Inc. 1990; Occupational Safety and Health Administration 1993]. Some primers are tailored to particular industries; others are more general.

This primer outlines the approach most commonly recommended for identifying and correcting ergonomic problems. This document offers practical information (based on NIOSH experience in a variety of settings) for applying elements of this approach in workplaces. The steps typically used to describe ergonomics programs are used here to tap and organize the NIOSH database of relevant experience.

Information about the techniques, instruments, and methods mentioned in examples of NIOSH work and other reference materials appear in the appendix, referred to as a Toolbox. Included in the Toolbox is a master chart listing details of NIOSH evaluations involving WMSDs reported over the past 15 years. Finding work settings or jobs in this chart that are related to the readers jobs may help the reader capitalize on the information contained in these reports, which are available from the National Technical Information Service (NTIS).

This primer is geared to those who need knowledge of ergonomics because of their roles as employers or as persons responsible for ensuring safe and healthful work conditions in their companies. Use of numerous examples from real workplaces emphasizes practical approaches. Organizations with established ergonomics programs or with a staff having advanced training in ergonomics may find more limited value in this primer.