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Ergonomic Guidelines

 

Workstyle Issues

Many people argue that injuries at the computer arise more from prolonged work in static, awkward postures than from the repetitive motion themselves. Frequent rest and stretch breaks are an important way to reduce muscle and joint fatigue, pain, and injury. Periodic eye exercise is important to reduce visual fatigue. Posters or pictures of outdoor scenes in areas where there are no windows can provide something restful to look at. Break reminder software can be a good way to remind users to take breaks.

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Work Surfaces

  • The support surface for keyboarding should be at approximately elbow height.

  • The work space should allow sufficient leg space and knee clearance so that the user can come as close to the keyboard as possible.

  • A matte finish should be used to minimize reflection.

  • Rounded corners on workstations are recommended so that arms and wrists do not come in contact with any sharp or square edges.

  • Use a document holder that is located just to the left or right of the screen. The document holder should be adjusted to maintain the document at the same height as the screen and the same distance from the operator's vision.

  • Writing surface should be provided (minimum dimensions 12 by 16 inches).

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Sit/Stand Workstations

Some people with chronic back problems cannot tolerate sitting for long periods but can work standing up. Others need to alternate between sitting and standing. Positioning guidelines for someone standing is typically the same as when sitting, although people often prefer to have the keyboard surface at a lower height relative to their elbows when standing.

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Keyboarding

  • The alpha-numeric portion of the keyboard should be centered directly in front of the computer user.

  • The computer user should be able to type without extending their upper arms out from their body and with their forearms parallel to the floor or at a slight downwards angle.

  • The user's wrists should not bend up or down when typing, maintaining a straight line with the forearm (neutral).

  • When possible, the keyboard should slope downward away from the user (negative tilt) as this promotes a neutral wrist position.

  • While pull-out, adjustable keyboard trays have some limitations; they are the best way to provide a range of working heights and angles.

  • Wrist rests are not always helpful as they encourage people to type with their wrists or heels of their hands planted on the rest. They should be used only during typing breaks-hands should float above keys during typing with the wrists kept straight.

  • Keyboards with sticking keys or with keys that require excessive force should be replaced.

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Mousing

It is important to note that more injuries appear to be generated from frequent mouse use than keyboarding alone. Accessing the Internet for research, etc., typically requires prolonged mousing.

  • The mouse should be kept at the same level as the keyboard and as close to the keyboard as possible to reduce reaching to the side. (Never place the mouse on a surface that requires the user to reach up and out to access it. Keyboard trays that do not provide sufficient space for mousing should be removed or replaced.)

  • The keyboard tray or work surface should provide sufficient room for the user to move the mouse with the forearm, not the wrist, helping avoid bending the wrist sideways.

  • When mousing, the wrist should be in line with the forearm (neutral position).

  • Utilizing keyboard commands is an important way to reduce mouse use.

  • For left hand users: Mouse cords should be long enough to permit relocating the mouse to the left side of the keyboard. Simple instructions should be available on switching the left and right mouse buttons through the Mouse Control Panel.

  • A range of sizes and types of mice are available to accommodate people with different-sized hands while alternate mousing devices such as trackballs can be essential for people with disabilities that impact their hand use.

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Monitors

  • The monitor screen should be directly in front of the computer user.

  • A good starting point for monitor placement is with the top of the monitor screen at the same height as the user's eyes, tilted backwards about 15 degrees, and at approximately arm's length.

  • Monitors should never be placed on top of the CPU, as tilting one's head back to view a monitor that is too high is fatiguing to the neck, shoulders, and eyes.

  • Screen resolution should be set at no more than 1024x800. Higher resolution settings as that make everything on the screen smaller and hard to see. (When individuals have difficulty seeing text or images on a screen, they will automatically lean forward to see it.)

  • Adjust screen brightness, contrast, etc. for comfortable viewing.

  • Screen display should be free from flicker.

  • Screen should have a minimally reflective surface.

  • Position the monitor screens at right angles to windows to minimize reflection and glare.

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Chairs

Chairs should be adjusted to fit the user. Comfort is the key factor in determining if a chair is fitted properly. Chairs should be easy to adjust, with clearly-labeled and intuitive controls.

Seat height

  • Feet should rest firmly on the floor

  • Upper legs should be almost parallel with the floor with the pelvis slightly higher than the knees (90 degree angle or greater at the hip joint)

Seat pan

  • Width should be at least one inch wider than your hips and thighs on either side

  • Depth should be adjustable either by a backrest with in-out adjustability or sliding seat pan.

  • There should be a space of 1-3 inches from the front edge of the chair to the back of the knee to avoid pressure on back of knees

  • The seat should have a rounded front edge to reduce pinching and improve blood flow to lower leg.

  • The seat should have 1-2 inches of padding with breathable upholstery.

Backrest

  • Lumbar support is provided through gentle curves in the backrest shape. Desirable depth and firmness of lumbar support is determined by different preferences and body shapes.

  • Height adjustability should allow individuals to change how the lumbar support curve contacts the back.

  • Provide backrest angle adjustment for reclining from vertical.

Armrests

  • Armrests can interfere with getting close to the work and reaching the mouse, so adjustability is essential. While a facility can manage with most chairs not having armrests, it would be important to provide some chairs with armrests for those with arm and shoulder weakness who require more support.

  • When purchasing chairs with armrests, specify that they be height and width adjustable and readily removable.

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    Footrests:

    • Footrests should be used when work surfaces are not able to adjust low enough for the user to be properly positioned at the keyboard with feet flat on the floor. In these situations, the chair should be raised to bring the user to the desired working position and a footrest provided to prevent the user's legs from dangling.

    • Footrests should have adjustable height and surface area large enough to comfortably accommodate both feet.

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    Lighting:

    • Light should be adequate for the computer user to clearly see text and screen, but not bright enough to cause direct or reflected glare.

    • Minimize variations in brightness levels between the screen and the surrounding surfaces. (Examples of poor lighting: a window or bright light source behind the monitor or working in a dimly-lit room.)

    • Flickering lights should be replaced immediately.

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    Alternate Devices and Supplemental Materials:

    • Document holder (Adjust to maintain document at same height and distance as the monitor screen.)

    • Trackball (Easier to use for people with hand and shoulder problems.)

    • Adjustable Split Keyboard (Promotes better hand position.)

    • Keyboard without 10-key pad (Brings the mouse closer to midline, reducing shoulder problems.)

    • Keyboard command cheat sheet. laminated at each work station

    • Ergonomic positioning guideline, laminated, at each workstation

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