Millions of people work with computers every day. There is no single "correct" posture or arrangement of computers that will fit everyone. However, there are basic design goals, as listed below, to consider when setting up a computer workstation or performing computer-related tasks.
Contrary to popular belief, sitting, which is thought by most to be a comfortable position, is actually hard on the back, legs, and feet. Sitting for lengthy periods of time can cause increased pressure on the intervertebral discs - the springy, shock-absorbing part of the spine. At the same time, gravity tends to pool blood in the legs and feet and create a sluggish return to the heart.
To obtain and maintain a high level of support and comfort when using your chair, perform the following recommendations:
- Adjust seat pan depth so that the back of your knees are approximately 2-3 inches out from the edge of the seat pan.
- Adjust chair height so that your feet rest flat on the floor and are your thighs parallel to the floor. (Use a footrest if necessary)
- Adjust chair lumbar support so that you sit upright in your chair with the lower back supported by the backrest.
- If used, adjust arm rests so that they provide light support to the forearms and allow your shoulders to be relaxed.
- Alternate between sitting and standing positions as you perform your daily tasks.
If you are like many computer users, your computer, keyboard, and mouse are resting on your desk or a portable computer workstation. There is no specific height recommended for your desktop; however, the working height of your desk should be approximately elbow height for light duty desk work.
To allow for proper alignment of your arms your keyboard should be approximately 1 inch to 2 inches above your thighs. Most times this requires a desk which is 25 inches to 29 inches in height (depending upon size of individual) or the use of an articulating keyboard tray.
Other desktop layout recommendations include:
- Organizing the desktop so frequently used objects are close to the user to avoid excessive extended reaching.
- If a document holder is used, it should be placed between the monitor and the keyboard to prevent frequent eye shifts between the screen and reference materials.
- Use a footrest if feet do not rest flat on the floor.
- Clear area underneath the desk to accommodate legs and allow for stretching.
- Use a headset or speaker phone to avoid neck and shoulder discomfort for frequent phone usage and multi-tasking.
KEYBOARD AND MOUSE PLACEMENT
Many ergonomic problems associated with computer workstations occur in the forearm, wrist, and hand. Continuous work on the computer exposes soft tissues in these areas to repetition, awkward postures, and forceful exertions.
The following adjustments should be made to your workstation to help prevent the development of an ergonomic problem in the upper extremities:
- Adjust the keyboard height so that you have approximately a 90 to 120 degree angle in the elbow.
- You should be able to relax your shoulders and allow your arms to rest at your sides.
- Your forearms should be approximately parallel to the floor while keyboarding and mousing.
- Position the keyboard and mouse close to you.
- The keyboard should be lying flat or slightly titled away (e.g., negative tilt) from you.
- Your wrists should be in a neutral position while keyboarding.
- The wrists should be flat or have a slight extension;
- The wrists should not be excessively deviated towards the midline of the body or away from the midline of the body.
- Use soft, easy key strokes.
- Rest hands on a palm support or in lap during rest pauses.
- Avoid resting wrists on hard/sharp surfaces/edges while keyboarding or using the mouse.
- The input device (e.g., mouse, trackball) should be located adjacent to and at the same height as the keyboard.
- You should be able to rest your forearm on the desk without excessive reaching.
- The angle between your arm and ribs should be less than 45 degrees.
With regard to the monitor, one must take into consideration how the placement and maintenance of the monitor can affect both the eyes and the musculoskeletal system. The following suggestions can help prevent the development of eye strain, neck pain and shoulder fatigue while using your computer workstation:
- Position the computer monitor so the top of the screen is at or just below eye level.
- Make sure the surface of the viewing screen is clean.
- Adjust brightness and contrast to optimum comfort.
- Position the monitor directly in front of you to avoid excessive twisting of the neck.
- Slightly tilt the top of the monitor away from you at a 10 to 20 degree angle.
- The monitor should be approximately an arm's length away from you to avoid eye strain.
- Position the monitor screen at a right angle to the floor.
- Position monitors at right angles from windows to reduce glare.
Lighting not suited to working with a Video Display Terminal is a major contributing factor in visual discomforts including eyestrain, burning or itching eyes, and blurred or double vision. Typical office environments have illumination levels of 75 to 100 foot-candles, but according to the American National Standards Institute, computer workstations require only 18 to 46 foot-candles.
Use the following recommendations to reduce eyestrain and eye fatigue:
- Close drapes/blinds to reduce glare.
- Point desk lights away from the monitor to reduce glare.
- Use indirect light or shielding (where possible).
- Place monitor at 90 degree angle to windows (where possible).
- Reduce overhead lighting (where possible).
- Walls should be covered with a medium color, flat or textured finish to reduce glare.
- Use an antiglare screen or monitor shield to reduce glare from overhead lighting.
- Position monitor such that overhead lighting is off to the side or behind one's head to avoid too much light shining into the eyes.
Regularly incorporate breaks throughout the work day to re-energize the body and minimize tension and stress.\
- Take frequent (1 every ½ hr) mini-breaks to get up and stretch or walk around.
- It is also important to change positions periodically.
LAPTOP COMPUTER USE
It has become more and more common to use laptop computers as primary computers. Such use presents several challenges, as the ability to position one's body in neutral postures becomes a bit more difficult. The following is recommended to help achieve neutral postures when using laptop computers:
- Experiment with table height, chair height, and keyboard angle to maintain neutral wrist postures.
- If you are seated in a side chair or couch, use a pillow to support your arms while keying.
- Attach an external mouse and keyboard instead of using the small constricted touchpad or trackball and laptop keyboard.
- Incorporate mini-breaks every 20 to 30 minutes to break up repetition and static postures.