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Mice more than a molehill [Industrial Engineer](Industrial Engineer Via Acquire Media NewsEdge) RESEARCHERS FIND ARM SUPPORTS HELP RELIEVE PRESSURES OF COMPUTER USE Researchers have crunched a lot of data figuring out the best ways to support hands and arms as they type on computer keyboards. The problem is that graphical user interfaces have evolved to the point where office workers use their computer mouse twice as much as their keyboard, said Jack Dennerlein, a professor in the Bouvé College of Health Sciences at Northeastern University. So Dennerlein and his colleagues at the Harvard School of Public Health and Kettering University tackled the issue in "Effects of Forearm and Palm Supports on the Upper Extremity During Computer Mouse Use," published in Applied Ergonomics. The paper also tackled a bit of controversy in the ergonomics world. Many practitioners believe that arm supports are detrimen- tal, but others say they're critical for computer users. The mouse has changed the way people work, Dennerlein said. Pointing and clicking are much more intuitive ways to interface, so users continue to move away from keyboard shortcuts. The paper's data showed that arm supports reduce shoulder flexion torques by 90 percent compared to no support. "Arm supports are fabulous for the shoulder," Dennerlein said. "They really reduce the shoulder load. They can promote more neutral postures for the shoulder." Ideally, users would have a whole tabletop to rest their forearms on. But, Dennerlein said, that can be difficult depending upon the worker's circumstances. For example, short people with thick desks might have to raise their shoulders too much, increasing the load there. "The support should be at the height of your elbows," he said. "You don't want it higher, and you don't want it lower. Higher means you're going to lift up your shoulders a lot and you're going to get shoulder pain. If it's lower you're not going to use it. So it has to be at that sweet spot in terms of the height." However, forearm support keeps the arm more stationary, so users rely on their wrists to do a little bit more. Dennerlein said adding palm support helped negate the effects of the wrist exten- sion, a finding he called important. The researchers had various combinations of forearm and palm supports, and using either support in isolation resulted in lower applied forces to the mouse pad. Dennerlein said more research is needed to determine the best type of mouse, but trackballs are nice alternatives. Some mice don't pronate your arm as much, and Contour makes a roller mouse, which is a bar that allows you to use any of your fingers. But there's just not a lot of data out there, he said. "The thing we often recommend is see if you can get a sample and try it out and see what works," he said. "Even getting a second mouse that's just completely shaped differently can make a differ- ence. It's sort of like two different pairs of running shoes. You change things up and that makes things better." How office workers place their hands also contributes, Denne- rlein said. You shouldn't rest on the middle of your wrist, the valley between your pinky foot and your palm. Instead, rest on the scaphoid bone. If your right hand is facing palm up, the scaphoid bone is on the lower right (lower left for your left hand) on a direct line below your thumb. Researchers used this experimental setup to measure posture, forces and muscle activity of computer mouse users. (c) 2014 Institute of Industrial Engineers-Publisher |