Sarasota PC Monitor

Ergonomic Tips (03/03)

The Computer Station

by John R. Chait D.C.,drchait@hotmail.com
Member of the Sarasota Personal Computer Users Group, Inc.

The importance of Computer Station design increases with the amount of time spent at the computer. As a general guide anyone who spends more than two hours a day in front of a PC should take special care to ensure the Computer Station is user friendly.

Ideally the chair, terminal and keyboard height should all be fully adjustable. When this is the case, the chair should be the first piece of furniture adjusted to fit the person operating their PC Once the chair has been properly adjusted it should be used as a reference point for all further adjustments. With the feet firmly planted on the floor and the upper body in a neutral position, the monitor and keyboard position should then be adjusted. Finally additional computer accessories including mouse or trackball, wrist supports and copy holders should be correctly placed. If the work surface height is not adjustable, the chair should be fitted to the Computer Station and a footrest provided to support the feet if needed. Specific guidelines for these adjustments are outlined in the following sections.

Chair

Computer users tend to spend most of their day seated. To provide comfortable support for each particular individual, the following features are important:

Chair Adjustment

  1. Stand in front of the chair. Adjust the height so that the highest point of the seat is just below the knee cap.
  2. Sit so that the clearance between the front edge of the seat and the lower part of the legs just fits a clenched fist.
  3. Adjust the angle and height of the backrest of the chair so that it supports the hollow in the lower back.
  4. Adjust the seat pan tilt to a comfortable position.

A chair should be adjusted many times during the day. This will help to relieve muscle tension in specific muscle groups while loading others.

If the work surface height is not adjustable, position the chair so that forearms are parallel to the floor, while keying. If necessary, provide a foot rest to support the legs and reduce strain on the lower back.

The monitor or screen of a computer should be positioned so that the top line of text is at eye level while seated. Distance from the eyes to the screen should be approximately arms length. Greater distances may contribute to poor posture, if the user leans forward to see the information on the screen. So adjust your computer font to be able to read it at arms length. In Windows XP, use your display properties appearance tab to make these adjustments. Set it for extra large fonts.

The monitor should be placed directly in front of the PC User, with a maximum of lateral angle of 30 degrees. Tilting the monitor so that the screen is vertical is also important as this position may reduce glare. These adjustments to the monitor help keep the neck in a more neutral position, minimize muscle fatigue and reduce glare.

Keyboard -- A Computer Station should accommodate the keyboard on a separate and adjustable surface. The keyboard holder should be long enough to accommodate a pointing device or mouse pad directly beside the keyboard and at the same height. It is important that both the keyboard and the keyboard holder be kept as flat as possible. This places the wrist in a more neutral position minimizing muscle strain.

The keyboard should be positioned at a height which allows the shoulders to be relaxed, the upper arm relaxed and close to vertical, the lower arm horizontal and the wrist straight.

Pointing Devices- The main pointing device used for computer work is the mouse. Shoulder, forearm and wrist discomfort can be significantly reduced if the mouse is used optimally. Tips on proper usage of a mouse include:

  1. Place mouse at the side of the keyboard and at the same level. Do not reach for it.
  2. Use the armrest on the chair or rest your arm on another available support while using the mouse.
  3. Reduce pressure on the wrist from the work surface; a mouse pad or rest may help.
  4. Rest your finger on the button; do not hold it hovering above the mouse.
  5. Keep the wrist straight; wrist angle should not exceed 20 degrees extended, nor be bent to either side.
  6. Do not grip the mouse tightly.
  7. Choose a mouse that fits your hand; many different sizes and shapes are available.
  8. Set your mouse speed at about the middle range.
  9. Reduce the time spent using the click and drag feature of the mouse as this puts strain on the forearm and hand. Software is available which will convert an extra mouse button to one which performs the click and drag function, or the double click function.

Newer computer furniture makes specific allowances for mouse position. Earlier computer furniture designs may require structural modification to accommodate the mouse or the selection of alternate pointing devices.

Alternatives to a mouse are increasing with the advancement of technology. Trackballs are a common alternative. They should have a minimum diameter of 3 inches. As well, gliding touch pads are available which are activated by the movements of the finger. Tablet pads (pen like substitutes) are also available. The advantages and disadvantages of these various input devices have not been well studied, and should be experimented with before purchase.

Wrist Support--- Foam pads placed in front of the keyboard known as wrist supports remove sharp, uncomfortable edges. Wrist supports tend, however, to be misused. Wrists should only be rested on the wrist support during pauses in keying and should not be rested on the wrist support while the user is typing.

Copy holder---Copy holders are recommended for individuals who perform input tasks from a source document. Copy holders eliminate frequent neck movements caused from looking back and forth between screen and paper, as well as continuous refocusing of the eyes. To maximize the benefits of a copy holder, it should be at the same height as the monitor, and as close to the monitor as possible. (See figure)

Bifocals---Bifocal wearers may tilt their head back to view the monitor through the lower portion of their glasses. In this case the monitor should be placed lower than previously recommended. The use of single focus glasses designed specifically for computer use may be the ideal solution for this situation.

Increased use of computers has caused a corresponding rise in health concerns directly related to their use. The most common health concerns are repetitive strain injuries, general muscle strain and discomfort and eye and vision problems. Computer Station design and proper PC practices can help to address these concerns.

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Copyright 2003. This article is from the March 2003 issue of the Sarasota PC Monitor, the official monthly publication of the Sarasota Personal Computer Users Group, Inc., P.O. Box 15889, Sarasota, FL 34277-1889. Permission to reprint is granted only to other non-profit computer user groups, provided proper credit is given to the author and our publication. We would appreciate receiving a copy of the publication the reprint appears in, please send to above address, Attn: Editor. For further information about our group, email: admin@spcug.org/ Web: http://www.spcug.org/

The Sarasota Personal Computer Users Group, Inc. has 1,100+ members and was established in 1982. We are members of the Assoc. of PC User Groups (APCUG), the Florida Assoc. of PC Users Groups, Inc., and we are members of the America Online Ambassador Program.

See http://www.spcug.org for all reviews from the Sarasota PC Monitor, go to the Newsletter Section.