September 2004

EVERYTHING IN BALANCE

By Lydia Dumyn

Relying on your dominant hand at work may not give you the upper hand when it comes to body balance.

While unilateral body use may be instinctive, occupational therapists warn that it may also prove risky when combined with the unnatural, unchanging or unceasing movements associated with repetitive strain injuries (RSIs). The solution, experts say, is to create physical balance through job rotation and variation.

Unilateral RSIs are becoming more common on assembly lines, in manufacturing and meat-processing plants, and at jobs requiring use of hand tools — from jack-hammering to carpentry, hairdressing and playing music. Dr. Sharon Switzer-McIntyre, assistant professor of physical therapy at the University of Toronto, says this may be the case because employers are assigning tasks that offer little or no variation.

“If one part of the body is used more than another, it’ll get stronger, provided it’s healthy,” Dr. Switzer-McIntyre says. “If there’s already an injury to a muscle or joint, it will only get weaker with use.”

Most people may not recognize they’ve sustained an injury until it becomes an inconvenience, she says. By that time, the injury can be difficult to treat and problems can snowball.

A Statistics Canada survey, conducted in 2000-2001, showed that 2.3 million people aged 20 and older reported having an RSI within 12 months of being polled. Of these, 25 per cent involved the neck and shoulder, 23 per cent the wrist and hand, 19 per cent the back, and 16 per cent the elbow. More than half were work-related.

RSIs are soft-tissue injuries to muscles, nerves, ligaments and joints, says Lorraine Mischuk of the Manitoba Society of Occupational Therapists. “These injuries can be a huge problem,” Mischuk says. “When one thing goes wrong, that injury can trigger others,” quickly migrating to the wrist and elbow, upper arm, shoulder, neck and back. Lynda van Dreumel, an occupational therapy consultant to assembly line and manufacturing workers, agrees. The body tends to create it’s own balance to a certain degree, van Dreumel says, and an injury can produce a “waterfall effect” when other body parts compensate for a loss.

The key to global body balance is maintaining muscle length, says Gayle Brown, a spokesperson for the Canadian Physiotherapy Association and an occupational therapist at the Workers’ Rehabilitation Centre in New Brunswick. Certain muscles shorten when they are overused, Brown explains. This causes the opposite muscles to stretch out, pulling unevenly on the spine and contributing to poor posture and RSIs, she adds. Contracted muscles squeeze the blood vessels, says information from the Canadian Centre for Occupational Health and Safety (CCOHS). Tasks requiring that arms be kept in a raised position — such as typing — mean the worker must stabilize the shoulder- neck region. To do this, muscles contract and stay that way until the task has been completed. The contracted muscles squeeze the blood vessels which, in turn, “restricts the flow of blood all the way down to the working muscles of the hand where the blood is needed the most,” the information says.

The neck and shoulders become fatigued — because of lack of movement — and the lack of blood flow to the limb accelerates fatigue and makes that part of the body more susceptible to injury.

Mischuk says avoiding unilateral RSIs comes down to reducing three things: awkward postures, force exerted by the hand, and repetition. Posture will likely be the first thing to go. “When you experience discomfort, you change the body position in which you work,” she says. “Even small changes in posture can cause considerable aches and pains.”

Good posture depends on where the work is being done in relation to the body. With an arm that’s held too high or too low, shoulder injuries can result and additional stress is put on the back.

A 2000 paper by the United Steelworkers of America recommends using adjustable workbenches and chairs. Surfaces should be high for precision tasks, and low for heavy manipulation and lifting.

The amount of force exerted by the hand using a tool depends on that tool, says the CCOHS. The greater the force required, the more recovery time needed. Worn, dull tools can increase operating force as much as tenfold.

Some employers have workers change jobs every few hours to address repetition, van Dreumel says. McIntyre cautions, however, that “if you’re doing the same job, but just switching work stations, you haven’t really rotated.”

Rotating jobs is an option, van Dreumel says, but she recommends retraining workers to alternate dominant and secondary hands. Acknowledging that the process can be frustrating, she notes that “the longer a person knows a job, the less likely they are to change their technique.”

When job rotation and alternating hands are not possible, Brown recommends stretching to help re-balance the system. “Whenever you’re doing a movement for an excessive period of time, take a break. Think about doing the opposite movement,” she says. “When you’re not feeling as well as you could be, you’re less efficient,” Brown says. “If employees actually stop for those 30 seconds every once in a while… and give their bodies some recovery time, overall productivity will increase.”

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