Canadian Researchers Develop Armrest That Can Help Prevent Repetitive Strain Injuries

UNIVERSITY of Guelph engineers said they have designed an armrest that reduces repetitive strain injuries and has the potential to be used in almost anything with a seat, from heavy machinery to powered wheelchairs.

Tests show the provisionally patented armrest reduces muscle activity in the neck by more than 60 percent compared to typical armrests, said Professor Michele Oliver, who has led the 10-year project.

While the armrest is about to be piloted in excavators, Oliver said the possibilities of the design extend far beyond heavy machinery.

"It's simple, cheap and relatively robust, so its potential uses are broad," said Oliver, who presented the idea of using the armrests on powered wheelchairs on June 17 at the Canadian Medical and Biological Engineers Conference.

The initial focus of the project was on designing an armrest for heavy-machinery operators because it's a line of work with high rates of repetitive strain injuries, she said. A joystick operator's limbs can go through 20,000 motions in a typical 10-hour workday. Only after completing the design did she realize the ergonomic armrest could revolutionize seat designs.

"Simple solutions are the most elegant, and this is a solution that will apply to any environment where a person is operating a control," she said.

Using computer simulations, Oliver and graduate student Greg Northey found that the neck muscles never get a chance to rest when someone is operating a joystick

Oliver said stationary armrests don't provide enough support for joystick users because the arm is left floating when it moves forward, and the shoulder is forced to rise when the arm moves backwards.

With the research obtained from the computer simulations, graduate student Taylor Murphy designed a moveable armrest that mimics the natural motion of the arm during joystick operations. Oliver said the armrest moves with the arm vertically and horizontally, relieving the shoulder from constantly stabilizing the arm and preventing strain on the neck muscles.

"It's the first-ever heavy-equipment armrest that moves and turns with the arm," Oliver said.

Oliver is currently working with a Canadian seat manufacturer for heavy machinery with the goal of retrofitting existing machines with the armrests and including the design in the production of future seats.

These dynamic armrests could be implemented in hundreds of thousands of work environments as early as 2010, Oliver said.

"It costs a couple of hundred dollars to build the armrest, which is a small price to pay considering the amount companies could save in Workplace Safety Insurance Board premiums," Oliver said.

Michele Oliver: http://www.soe.uoguelph.ca/webfiles/moliver/

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