Ergonomics: Workplace Risk Assessment Strategies

Workplace injuries due to repetitive motion cost employers an estimated $2.8 billion in 2002, according to the latest data from the Liberty Mutual Workplace Safety Index.

If that figure isn't enough to convince you of the importance of developing an ergonomics component in your safety program, consider that repetitive motion was the fourth-leading cause of on-the-job injuries in 2002 and 2001, according to the Liberty Mutual Research Institute for Safety.

In what will be the first in a continuing series on ergonomics, asked ergonomics expert Paul Adams, Ph.D., PE, CSP, CPE, a senior consultant with Ann Arbor, Mich.-based Applied Safety and Ergonomics Inc., to provide an introduction to the risks associated with repetitive motion and to offer an overview of some risk assessment strategies. Adams' background includes 6 years as the safety engineering and ergonomics leader for Toledo, Ohio-based fiberglass materials maker Owens-Corning.

For starters, Adams breaks all injuries into two categories: acute trauma and cumulative trauma.

Acute trauma refers to injuries that most people would associate with an accident: a worker getting his or her leg caught in a machine, an injury resulting from falling through an unguarded roof opening or "when a chandelier falls on your head," as Adams puts it.

Repetitive stress injuries fall into the category of cumulative trauma, which refers to the breaking down of the body's soft tissues as a result of many factors, including excessive force, repetitive motion, bad posture, vibration, temperature and personal traits such as diabetes, obesity and prior injury, according to Adams.

"When you have a combination of these risk factors come together, that's when a person is most at risk for developing cumulative trauma disorders," Adams said.

Cumulative trauma disorders include:

  • Carpal tunnel syndrome, a common -- and often painful -- condition that affects the hand and wrist.
  • Back strains.
  • Raynaud's syndrome (also known as white finger), a condition in which the smallest arteries that bring blood to the fingers or toes constrict, causing spasms.
  • Hand-arm vibration syndrome, which can cause numbness, discoloration of the fingers and hands, loss of grip strength and even a permanent loss of sense of touch and pain perception.
  • Epicondylitis, also known as tennis elbow.
  • Tendonitis, an inflammation, irritation and swelling of a tendon, which is the fibrous structure that joins muscle to bone.

The symptoms and the severity of symptoms associated with cumulative trauma disorders vary widely from person to person based on their job tasks and physiological traits, Adams says. Also interesting to note is that before they walk in the door some workers already have a "background prevalence" -- a predisposition -- to cumulative trauma disorders, according to Adams.

"Some people will get carpal tunnel even if their job is to test mattresses," Adams said. He noted that estimates vary on what percentage of the population has a predisposition to carpal tunnel. "Some says it's less than 2 percent, others say it's 5 to 6 percent. My guess is it's somewhere in the middle."

That doesn't make life easier for safety managers charged with identifying at-risk job tasks and mitigating the risk of cumulative trauma in the workplace. Compounding the confusion is that cumulative trauma disorders can be brought on -- or at least exacerbated by -- what the worker does outside the workplace.

"You might have people that ride motorcycles for a hobby and as a result get Raynaud's syndrome or a back strain," Adams said. "Or you might have someone at home who's an avid guitarist or a string instrument player or a quilter" and as a result suffers from a cumulative trauma disorder.

As for the factors that safety managers can most easily control -- those in the workplace -- the first step in trying to minimize those factors is to identify the jobs and work tasks that might contribute to cumulative trauma disorders. To do that Adams offers several strategies:

1. Look for patterns. The more obvious red flags are jobs that have a pattern of injuries associated with cumulative trauma. (OSHA recommends reviewing and analyzing OSHA 300 logs and other injury and illness records to find such patterns.) But Adams also recommends looking closely at jobs or tasks associated with high turnover, absenteeism or complaints. "Those are some of the early warning signs," he said.
2. Analyze the job tasks for potential ergonomic risks. The risks inherent in some job tasks should be fairly obvious -- for example, jobs that require the use of vibrating power tools such as jackhammers, power hammers, chainsaws, sanders, grinders and drills can expose workers to the risk of hand-arm vibration syndrome or Raynaud's syndrome. Material handling types of tasks often present a high risk of back strains. In general, OSHA recommends looking closely at jobs that involve:

  • Awkward postures;
  • Forceful lifting, pushing or pulling;
  • Prolonged repetitive motion;
  • Contact stress; and
  • Vibration.

3. Talk to your workers. OSHA's suggestions include conducting symptom surveys and employee questionnaires. Adams adds, "You also can ask people what are the hardest jobs out there. Typically that's a good place to start."

4. Look at your industry. Which job tasks within your industry are associated with a high number of cumulative trauma-related injuries? "If other companies in the same industry have ergonomic-related problems, then it is possible these potential problems are also your concern," OSHA says on its Web page dedicated to ergonomics.

5. Use risk assessment tools. When it comes to the risk assessment tools that are out there, Adams cautions that it's not a perfect science but rather "the best we can do" based on the research that's been done to this point on ergonomics. Still, these tools can give safety managers a better idea of the ergonomic risks associated with particular jobs. Some helpful tools include:

  • Applications Manual for the Revised NIOSH Lifting Equation, which contains a complete description of all terms in the Revised NIOSH Lifting Equation with several sample calculations.
  • Liberty Mutual Manual Materials Handling Tables, which can be used to perform ergonomic assessments of lifting, lowering, pushing, pulling and carrying tasks.
  • Lessons for Lifting and Moving Materials, by the Washington State Department of Labor and Industries, which provides pertinent information for safety professionals and manufacturing supervisors on back anatomy, back injuries and methods to avoid the risks of back injury. A checklist, Lifting Hazard Assessment Worksheet, based on the 1991 Revised NIOSH Lifting Equation, completed with a score of 6 or higher means the lift is unsafe. The guidebook is part of the Washington state agency's offering of analysis tools that can be found at
  • Analysis tools by the University of Southern Florida. The Web site provides a clearinghouse of ergonomics tools, including the Rodgers Muscle Fatigue Assessment, the Rapid Entire Body Assessment, the American Conference of Governmental Hygienists' threshold limit values for vibration and several of the tools already mentioned here.
  • OSHA's ergonomics Web page, which in addition to listing risk assessment tools, has a wealth of information, resources and links on the subject of cumulative trauma disorders.

Next week, an ergonomics expert will share some strategies aimed at minmizing the risk of cumulative trauma disorders in the workplace.

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