Canadian Occupational Safety

24 Canadian Occupational Safety | www.cos-mag.com QA M ost office workers spend long periods of time at a desk, seated in the same position for many hours every day. The health risks associated with prolonged sitting are made worse by poorly designed work stations that promote poor postures and lead to musculoskeletal disorders (MSDs) and repetitive strain injuries (RSIs). We look at some of the most common issues that office workers have and suggest what health and safety professionals can do to fix them. QUESTION: When I'm at work, I often get pain in my neck and shoulders. Why is that? Answer: Most common ergonomic complaints — lower back pain, pain and discomfort in the arm, wrist, neck and shoulder and, less commonly, in the leg and knee — are caused by work stations that are improperly set up. A proper set-up promotes a neutral posture (a comfortable posture in which the joints are aligned) and allows the body to be supported as much as possible to reduce muscle activity during the day, says Wayne Albert, dean of the faculty of kinesiology at the University of New Brunswick in Fredericton. "Muscle is biological tissue and it will fatigue over the course of the day. And when it gets tired, that's when injury is more prevalent." The problem is often height differential, he says. Ideally, a person who is five feet one inch tall should be seated at a desk that is about 24 inches high. For every additional three inches of worker height, the desk should be another inch higher. Thus, a person who is six feet tall should work at a desk that is 27 inches high. Albert estimates 80 per cent of the calls he gets are from women who, generally shorter than men, have trouble with the standard desk height of 30 inches. "They're usually working at a work surface that is much too high. Therefore, their arms are elevated, their wrists are bent backwards and their neck has to extend to be able to read the screen." Often too, the chair doesn't fit the worker. It may be an ergonomic chair, but if it is too large, the per- son's back cannot engage with the back rest. All the mechanisms in the back rest designed to off load muscle activity are removed. "So, as soon as you have to go into a non-neutral posture of your body, the muscles have to kick in. And when your muscles have to work all day, they get tired, they get sore and you end up with the pain," Albert says. Another important aspect of the chair is the seat pan, which may be too large or too short. If a seat is too small, workers tend to perch on the edge of the chair. If the seat is too large, it may catch the sitter in the back of the knees, compressing the nerves and blood flow, which may also cause the worker to perch forward on the edge of the chair. The chair then becomes a stool, and the worker will get no advan- tage from the backrest, whose purpose is to support the back muscles while the person is sitting. More- over, on a chair that's too large, the arm rests will not be where the worker's arms are naturally placed. The worker will sit between the rests and not receive the support that off-loads the arms and shoulders. Q: I spend many hours a day at my monitor and often end up with pain in my hand, wrist or forearm. What can I do about it? A: The height of the work station is part of the cause of discomfort here, too. But another reason for hand and wrist pain is how the worker uses the mouse. Instead of moving the wrist back and forth when moving the mouse, the worker should use the forearm, keep the hand straight and pivot from the elbow. The hand should be in neutral (in line with the forearm), and the forearm should be parallel with the floor. The worker should not extend the wrist so that it is bent sideways, in an upward posi- tion or in a downward, flexed position. Q: When I sit back in my chair, my feet don't touch the floor. Is this normal? A: When a work station is properly set up, the work- er's feet should be flat on the floor. In some cases, a short person may have the chair raised to accom- modate the height of the desk but, consequently, his feet do not touch the floor. In such a situation, it's important to provide a foot rest to support the feet, says Gary Friesen, ergonomic consultant at Friesen Ergonomics in Edmonton. Q: How do I set up an ergonomically correct work station? A: The surest way to achieve the proper ergonomic set-up is to provide customized desks, each one being the right height for the particular worker, Albert says. A less expensive option is to shorten the desk legs to the appropriate height. In about 90 per cent of the organizations he has dealt with, Albert says the preferred solution is simply to cut the desk legs down. Later, if the desk is given to a taller person, a safety manager can raise the desk up by placing blocks of wood under the legs. It's also possible to buy pre-formed blocks or cups made of rigid plastic that can be placed under the desk legs to raise the desktop. "It's like creating an adjustable desk without having to buy a new desk," Albert says. When purchasing new equipment, look for adjustability, he adds. Adjusting desks and chairs is the easiest way to fix ergonomic problems. Setting up work stations properly can help office workers avoid health problems that often lead to MSDs & OFFICE ERGONOMICS By Linda Johnson

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