In 1997, NIOSH (National Institute for Occupational Safety and Health) released a publication called Musculoskeletal Disorders and Workplace Factors, A Critical Review of Epidemiologic Evidence for Work-Related Musculoskeletal Disorders of the Neck, Upper Extremity, and Low Back http://www.cdc.gov/niosh/docs/97-141/pdfs/97-141.pdf . Although this report over 20 years old, the valuable information about what causes work-related injuries remains current.
One of the most interesting parts of the report is the evidence of work-relatedness to injuries. From the 40 epidemiologic studies they evaluated, NIOSH judged how strong they felt the evidence was that the injury or musculoskeletal disorder (MSD) was caused by the ergonomic risk factor. Ergonomic risk factors include: force, repetition, awkward postures, and static postures to name a few. The categories they used were:
- Strong Evidence of Work-Relatedness (+++) – a causal relationship
- Evidence of Work-Relatedness (++) – convincing epidemiologic evidence for a causal relationship
- Insufficient Evidence of Work-Relatedness (+/0) – could not conclude the presence or absence of a causal relationship
- Evidence of No Effect of Work Factors (-) – the specific risk factor is not related to MSDs
What they found for the neck and shoulder area was this:
- Evidence of Work-Relatedness (++) between highly repetitive work and neck and neck/shoulder MSDs. Repetitive work was defined as activities which involve continuous arm movements which affect the neck/shoulder muscles.
- So for people who have jobs like painting overhead or lifting to higher levels in a warehouse on a continuous basis, there is evidence that their work causes neck and neck/shoulder injuries. Even people who keyboard and mouse all day are at risk if their keyboards and mice are too high (activates the trapezius muscle in the neck).
- Proper use of ladders and the installation of a keyboard and mouse tray would be good ergonomic interventions here.
- Evidence of Work-Relatedness (++) between forceful exertion and neck MSDs. Forceful work was defined as powerful arm or hand movements, which generate loads to the neck/shoulder area.
- People who do heavy assembly work overhead or construction work would be at risk here.
- Lowering assembly work levels and rotating jobs in construction should reduce risk.
- Strong Evidence of Work-Relatedness (+++) between high levels of static contraction, prolonged static loads, or extreme working postures involving the neck/shoulder muscles and neck and neck/shoulder MSDs. Static contraction and loads refer to postures being held for a long period of time. Extreme postures would involve overhead reaching, bending, and squatting usually combined with twisting and reaching beyond comfort levels.
- People who carry trays of food in banquet halls or move furniture or appliances would be at risk for prolonged static loads. People who have to work in confined areas with very awkward postures and reach would also be at risk. And people who keyboard and mouse all day with their shoulders hunched due to their keyboard and mouse being too high would be at risk too.
- Weight limits on trays, lift assists for furniture and the installation of a keyboard and mouse trays would be helpful here.
In my next several posts, I will be discussing other areas of the body where there is evidence of work-relatedness to various injuries and identifying further jobs where there may be risks. Ergonomic interventions will be included too.