The Science of Ergonomics

Preventing Stress Injuries Before They Happen

By Charles Green

Like many people, I've been injuring myself every day, without even knowing it. Through bad posture and repetitive motion, I've put incredible strain on my muscles, joints, and tendons. Overusing these body parts can cause painful and disabling conditions such as carpal tunnel syndrome, tendinitis, and myofascial pain. These injuries are collectively known as repetitive strain injuries or musculoskeletal disorders.

According to the Web site of the Ergonomics Institute at the University of California at Los Angeles , “The average person working at a keyboard can perform 50,000 to 200,000 keystrokes a day.” Unless you set up your workstation properly, adjust your typing technique, and take frequent rest breaks, all those keystrokes can take a heavy toll on your fingers, wrists, arms, and back. Repetitive motion can lead to compression or entrapment of nerves in these places. Carpal tunnel syndrome, for example, is caused by compression of the median nerve at the carpal tunnel, located at the wrist and hand. Numbness or tingling in the thumb, index or middle finger, and one-half of the ring finger are often the first symptoms, as well as waking up at night from the hand “falling asleep.” Tendinitis and myofascial pain are two other common conditions of tendons and muscles.

Tendinitis can result from inflammation of the tendons or tiny tears in them, caused by overuse, or from remaining in a static or prolonged position for too long. The condition is found mainly in the fingers, thumbs, forearms, elbows, and shoulders. Symptoms can range from specific aches, stiffness, tightness, and burning sensations to a deep nonspecific pain. Left untreated, tendinitis can result in difficulty holding onto objects.

Myofascial pain is a diffuse, achy pain caused by tiny tears in the muscles, formed through overuse. Over time, these tears form scar tissue and result in inflammation and muscle stiffness. Overusing any muscle can also lead to tender spots known as trigger points on the muscle, and both myofascial pain and trigger points can result in disruption of sleep patterns.

How can we avoid these painful and disabling repetitive stress injuries? Here are some suggestions from the Ergonomics Institute:

•  Warm up and stretch before you start activities that are repetitive, static, or prolonged.

•  Take frequent breaks from any sustained posture every 20–30 minutes and stretch stiff muscles.

•  Respect pain. Change positions or stop whenever activities cause pain.

Posture is also a crucial aspect of preventing these injuries. Keep your back and neck erect and your shoulders relaxed. Keep your upper arms close to your body, your elbows at 100 degrees, your forearms neutral so that your thumbs point toward the ceiling, and your wrists straight. Avoid motions that twist and bend the back. Make sure your feet lie flat on the floor when you sit, by either adjusting your chair or using a footrest.

According to the Ergonomics Institute, there is a safe zone of movement, about 15 degrees in all directions, for your wrists. You should keep your wrists in as neutral a position as possible and avoid extreme motions. The same goes for your neck. Avoid bending it forward for extended periods of time. If you are typing from a manuscript, place the document on a holder beside or below your computer screen.

And avoid staying in one position for prolonged periods, as muscles fatigue faster when you hold them in one position. Keep moving to increase your blood circulation. In addition, the institute recommends that whenever possible you should alternate activities frequently throughout the day. Rotate heavy or repetitive tasks with lighter, less-repetitive tasks.

Adjusting your desk to minimize stress on your back, wrists, and fingers will also prevent repetitive stress injuries. Your chair is particularly helpful for easing stress. When sitting, push your hips as far back as they can go. Adjust the back of the chair to a 100-degree reclined angle. Make sure your upper and lower back are supported. If you need to, use inflatable cushions or small pillows to help provide support. If your chair has an active back mechanism, use it to make frequent position changes. Adjust the height of your seat so your feet are flat on the floor and your knees are as high as, or slightly lower than, your hips.

It is also essential to keep your keyboard in the proper position. Pull up close to it and position it directly in front of your body. Determine which section of the board you use most frequently and readjust it so that section is centered in front of your body. When using the keyboard, keep your shoulders relaxed, your elbows in a slightly open position, and your wrists and hands straight. Adjust your keyboard so that your body rests in this position.

In addition, adjusting your computer screen can help. If you can, center it directly in front of you, above your keyboard . Place the top of the monitor approximately 2 to 3 inches above seated eye level. Sit at least one arm's length away from the screen and then adjust the distance for your vision. To reduce glare from the screen, which can aggravate strained muscles, place the screen at a right angle to windows. Make any necessary adjustments of curtains or blinds. You can also adjust the vertical screen angle and screen controls to minimize the glare from any overhead lights.

If you use source documents when typing, place them directly in front of you, between the monitor and keyboard, in an inline copy stand, or, if there is not enough space, on or in a document holder adjacent to the monitor. And put your telephone within easy reach, using stands or arms if necessary.

Of course, work is only one place where we can encounter repetitive stress injuries. Even seemingly simple tasks such as bending and lifting can put incredible stress on your body, which can result in painful, debilitating conditions. Here are some recommendations from the Ergonomics Institute for safe, proper lifting that will prevent back pain.

•  When lifting, hinge at your hips and bend your knees. Your legs, rather than your back, should be doing most of the work. If you have difficulty bending your knees, keep a wider stance.

•  Tighten your stomach muscles before you lift. This helps support and stabilize your back while lifting.

•  Keep objects close. Did you know that a 10-pound bag of groceries can put 100 pounds of pressure on your back? Holding objects farther away from your body greatly increases this pressure.

•  Whenever possible, use your hands and arms for added support. Use a golfer's lift [lean one hand on a stable object, maintain a neutral spine, and pivot forward from the hips, while allowing the opposite leg to raise up behind you] to retrieve light objects or when reaching into low containers like hampers or shopping carts.

•  When lifting and moving objects, pivot with your feet. Turn your whole body instead of twisting your spine, especially if you are holding heavy objects. Your nose should always be in line with your toes.

•  Balance objects when you carry them. Whenever you can, use dollies and carts for heavy objects. Use your body weight to push the dolly or cart with your legs rather than pulling with your back.

By making some simple changes and keeping them in mind, we can all enjoy less pain and more productivity.

Freelance writer and editor Charles Green lives in Annapolis .