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Guidelines for computer workstation adjustments

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Adjusting a VDT workstation is neither complicated nor technical. Begin with the chair and, after adjusting the chair to the most comfortable position, proceed to other workstation components. Refer to the following guidelines for adjustment tips and ideas.

Chairs

A chair should fit the person using it and the task for which it is intended. Here are the key factors in selecting and adjusting a chair:

  • Stability – Use a chair that has good stability (five-point base).
  • Seat – The preferred seat-pan length allows for space between the front edge of the seat and the back of the lower leg, at the knee, while the users back is contacting the backrest.
  • Seat-pan angle – Preferably, the seat back should be moveable independently from the seat pan. The user should be able to lean back slightly to modify the pelvic angle at random.
  • Seat-pan height adjustment – The height of the seat pan should be easily adjustable by the user when seated.

Ideally, the chair height should be adjusted first, followed by adjustment of other workstation components. If the work surface is too high, the chair height will need to be adjusted upward until the hand, wrist, and forearm are parallel to the keyboard and slightly above the keys. A footrest can be added as needed to compensate for the increased chair seat height.

Seat-Pan Shape and Padding

The front edge of the seat should preferably have a rounded profile. A straight seat pan front edge tends to compress nerves and blood vessels behind the knee, sometimes causing discomfort and tingling in the lower extremities. The seat-covering material should be porous and breathable. Slippery seat pans may cause the user to slide away from the backrest, producing a loss of lumbar support.

Hard, unpadded seat pans are uncomfortable to use. In contrast, soft, deeply padded seat pans may cause the user to sink too far into the seat. A seat should be selected with padding somewhere between these two extremes.

Backrests

Backrests should have a 15-20-inch-high support surface, a width ranging between 14-16 inches, and be vertically adjustable above the seat pan. The backrest should also be moveable independently from the seat pan to allow the user to lean back slightly at their discretion. A good backrest will support the lumbar region of the back, but not be so large that it interferes with use of the arms while performing tasks.

Armrests

Armrests should be optional. When properly used, armrests reduce muscle loads on the neck, shoulders, and arms; reduce pressures in the spine, assist rising and sitting in the chair, and support task-related movement. If chairs have armrests, they should be adjustable to the user's width and height, and they should allow the chair to fit under the work surface without interference. Avoid adjusting armrests too high; in that position, they may cause shoulder discomfort. Overall, evidence shows that armrests are beneficial when they are adjustable and follow task-related postures and arm positions.

Display screens

The display screen should be adjusted so that the topmost line of viewable text on the screen is at or slightly below the user’s line of vision. The display should also be located as far away from the user as possible while still allowing for comfortable viewing. Bifocal users may need to locate their monitors lower on the work surface to minimize tilting their heads back while reading through the bottom portion of their lenses. Screens that swivel horizontally and tilt or elevate vertically enable the operator to adjust the screen for the best viewing angle. Sometimes, a display screen may need to be mounted on an adjustable arm to allow for comfortable positioning.

Pointing devices

The mouse or pointing device should be located directly alongside the keyboard and to either side of it. Once the mouse or pointing device is properly placed, the user should be able to use it comfortably while maintaining the upper arm parallel to the torso. Also, the hand, wrist, and forearm should be held in a reasonably straight, horizontal position when using the input device. A wide variety of input devices are currently available. One should be chosen meeting user preference, and it should be used according to these general principles.

Keyboards

Most of the currently available keyboards are suitable for occasional or routine computer use. If you can, choose one with a thin profile. It should be positioned in a manner which minimizes bending of the wrist during use. For best results, the user should arrange the workstation so that the keyboard can be reached comfortably and without over-reaching. Although not a requirement, some users may wish to place a wrist rest in front of the keyboard, in order to help maintain a ‘'neutral" wrist posture.

Document holders

If used, the document holder should be stable and adjustable for height, distance, and angle of view. It should fully support the source material and can be placed by user preference on either side of the monitor. In some situations, the document holder may need to be placed between the keyboard and the monitor. In all cases, placement of the document holder should aid the user in viewing source material without uncomfortably twisting the neck on a prolonged, repeated basis.

Work surfaces

For intensive computer work without interruptions, use of a worktable with a height adjustable surface and a separate, adjustable keyboard shelf is recommended. The adjustable keyboard shelf should accommodate both the keyboard and the mouse on the same level. Adequate clearance should also exist underneath the workstation.

If a fixed-height worktable is used, an adjustable-height keyboard tray should be available. The keyboard tray should be wide enough to accommodate both the keyboard and the mouse, and the height adjustment mechanism shouldn’t interfere with clearance underneath the workstation. An adjustable-height keyboard tray also allows the worksurface to be used for tasks such as writing, answering the telephone, and staging reference materials.

Footrests

If an operator’s feet do not rest flatly on the floor once the chair height has been properly adjusted, a foot rest may be needed. Many different types and styles of footrests are available. One should be selected suiting user preference, and it should be easily moveable in order to avoid becoming a tripping hazard. A footrest should only be considered after all other workstation adjustment options have been exhausted.

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