Are you getting off work feeling good, or massaging a throbbing wrist or crick in your neck that seems like it’s never going to go away?

If it’s the latter, we have one word for you: ergonomics. You probably need to tweak your office setup to protect your body from ongoing insults. More than a third of all workplace injuries (many from repetitive motions such as typing) result from poor ergonomics, according to the U.S. Bureau of Labor Statistics.

Even if you spend your day at a desk, you need to pay attention to your body just as a construction worker would to avoid suffering the kind of strain that can lead to pain and disability, says Julie Landis, DPT, a physical therapist and spokesperson for Briotix, an ergonomic consulting company based in Centennial, Colorado.

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Landis repeatedly sees the same mistakes that put employees at risk. Here are her top blunders to avoid.

The wrong chair height. Too many people spend their days in a chair that is actively working against their health, Landis says. The chair should be high enough so your elbows are even with the keyboard, but it shouldn’t be so high that your feet don’t reach the ground. (Shorter people may need a footrest to keep their feet from dangling.) Your knees should be even with, or just a bit lower than, your hips.

Knobs and levers on office chairs are there for a reason, so learn how to use them. “People don’t know how their chairs adjust,” Landis says. Many times, she has been able to save workers who struggled with a wobbly chair by simply tightening a knob. “They often laugh at first because it was so easy to fix,” she says. “But it’s not really that funny, because they were in pain.”

The wrong monitor placement or settings. Many people strain their eyes by putting their faces too close to a screen. The monitor should be an arm’s length away. If text is hard to read at that distance, adjusting the brightness or contrast is a much better strategy than leaning closer to the screen. Ideally, any sunlight that reaches the office should hit the monitor sideways, not directly onto the front or on the back.

To keep your eyes from tiring, Landis recommends a 20/20/20 break: Every 20 minutes, close your eyes for 20 seconds and then stand up and stare 20 feet into the distance.

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A keyboard that’s too high, too low or far away . If you’re using a laptop, as a general rule it’s better to use a separate keyboard in a keyboard tray (and a separate monitor) so you can look at the screen without hunching over. If your hands are higher than your elbows, that’s too high.

Get close enough to the desk so you’re not straining when you type. Your arms should never be stretched out as you type.

Hunching over and stretching out your arms are recipes for tendonitis, or inflammation of the tendons.

A badly placed mouse. When using a desktop computer, the mouse should be on the same level as the keyboard. If the keyboard is lower than the mouse — perhaps because it’s on a tray — moving back from one to the other will cause avoidable strain.

Complacency. This is perhaps the biggest hazard in an office, Landis says. In her view, too many workers — and their bosses — fail to take comfort and safety seriously. She says everyone in the office should take the time to learn about the basics of ergonomics and let higher-ups know if a workstation isn’t up to par. “People need to take an active role in their own well-being,” she says.

Even if your ergonomics are perfect, your body isn't meant to stay in the same position for hours. Whether you work in an office complex or a home office, Landis encourages you to move often, if only to stand and shake off the cobwebs. Getting up every 15 to 20 minutes is a good place to start. A 10-minute walking break at lunch can loosen up the body and energize the mind. A Fitbit or similar device can be set to vibrate every 20 minutes — a good reminder that it’s time to get the blood flowing.

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Chris Woolston, M.S. is a freelance writer and editor who specializes in science, health and travel. A reformed biologist, Woolston says, he studied algae and nitrogen dynamics in Antarctic lakes before the Science Writing Program propelled him out of the lab. He is a contributing editor at Nature.com, a former staff writer for Time Inc.’s Hippocrates magazine, and co-author of Generation Extra Large (Perseus). He lives in Billings, Mt., with his wife – novelist Blythe Woolston – and their two children.