The best chair has an adjustable seat height. Adjust it so that your feet rest on the floor (or on a footrest), your legs form a 90-degree angle at the knees, and your thighs are parallel to the floor. It should have good lumbar support and a back tilt adjustment so that you can sit at a slight recline and also shift your upper body position. Don’t use the arm rests while typing.
Position your monitor so that you don’t have to turn your body or twist your neck. It should be arm’s length away—about 18 to 26 inches. Adjust the height so that your eyes are in line with a point about two to three inches below the top of the monitor. This allows you to keep your head upright with your chin tucked (rather than your head tilted back or your neck flexed forward). If you need to raise the monitor, stack some textbooks, phonebooks or other stable object underneath. To avoid glare on the screen, place the monitor perpendicular to the window, if possible, and away from direct lighting.
When working with a mouse or keyboard, your hands should be at elbow height or slightly lower. Keep your elbows at a more open angle rather than flexed, and your forearms, wrists and hands in a straight line. The keyboard should be at a comfortable distance, not so far away that you have to reach to touch the keys. When typing, relax your shoulders with your elbows close to your sides. When using your mouse, make sure your wrist is straight, not bent to either side; gently cup the mouse with your hand; don’t flex your thumb.
You should not use your laptop on your lap (as pictured). Tilting your head to see the screen can cause neck strain. The keyboard should be at elbow height, and your hands and wrists in a straight line. If touchpad makes your thumb sore, attach an external mouse. If you use your laptop as your home computer, consider an external monitor and keyboard. No matter how light your laptop is, carrying it around can contribute to back, neck and shoulder aches. Rather than a shoulder bag, use a padded backpack that distributes the weight more evenly. Or use a wheeled luggage cart.
When working on a computer, take mini-breaks every 20 minutes, or as often as possible. Do shoulder shrugs and some neck, wrist and low back stretches. Every so often, stand up and do a full-body stretch. There are software programs that can teach you stretches and remind you to do them.
To ease eye strain, look away from the monitor every 15 minutes and focus on a distant spot. Then blink for a few seconds to help keep your eyes moist. You may need a special pair of glasses for computer work; talk to your eye doctor. Avoid extended periods of time on the computer. Switch to a noncomputer-related task when you can.