Number 204 - May 2000
Ergonomics of Your Personal Computer Station
by Marvin W. Eidinger, Tacoma Open Group for Micros
from September 1994 TOGGLE
   Man's introduction to machines of all sorts gives him the ability to experiment in ways never thought of by those who have only the use of their physical bodies. Some machines can make his life easier and some more difficult, and some even harmful. We do get intrigued by the many endless opportunities offered by our latest item, sometimes known as, the "mind" machine. Yes, it is a real mind teaser and most of us enjoy the thrill of conquering a small portion of its unlimited offerings. In fact, we get so involved we forget about the detrimental health issues we may be running into. Thus, the topic most of us have not been introduced to; the ERGONOMICS OF YOUR PERSONAL COMPUTER STATION. "Ergonomics", "Ergonomics", "Ergonomics", is this just another buzz word for the computerist? We already have several mouthsful (sic) of computer-type words that the ordinary man can hardly understand. Are we about to add one more?

   The word "ERGONOMICS" was first used in Europe just before the 1920's. The general use of "ergonomics" in the United States during the early 1980's made it sound like the latest buzz word much like "high-tech". Actually, it had been here since the early 60's, nobody thought much of it since--the phrase "human factors design", or "human factors engineering" was in common usage.

   The purpose of ergonomics is to perfect the unitizing of man with his machine so as to promote accuracy, speed of operation, and, during the same period, ensure the minimizing of fatigue, and negative health effects upon the human operator. Quoting the Webster Comprehensive Dictionary (Encyclopedic Edition, 1988), "ergonomics: The study of the relationship between man and his working environment, with special reference to anatomical, physiological, and psychological factors; human engineering."

   Now that I've got your attention, I would like to enlighten you with some key considerations, ideas, and worthwhile projects to make your short and long term computing comfortable, and, to assure the minimizing of your future health problems. There have been many articles in recent times about computer, word processor, and data entry operators having health problems resulting from employers' ignoring ergonomic issues in the work place. Be that as it may, you have the full control of these issues at your personal computer station. So, take the opportunity now to learn and then follow-thru (sic) with the necessary actions for your own benefit.

   Let me express to you what I found through my experiences in dealing with the ergonomic issues during the period 1981 thru 1984 (my present day observances indicate things haven't changed yet!!) of which the following were common examples:

   1: Hundreds (even thousands) of dollars were spent on equipment, but only a few dollars toward an ergonomic (healthy) work station.

   2: Witnessed situations:
      A: TNT classified ad taker sitting on a draftman's stool while typing on a word processer because the counter was orginally made for standing note writing.
      B: Boeing having computer on desk and the employee pulled out pencil drawer to place keyboard.
      C: Aurora Rental had operator facing visual display (monitor) with picture window to outside in the background.
      D: Several offices with overhead fluorescent lights with monitors reflecting same into the operators eyes.
      E: First Interstate Bank office (24th & Pacific) having their word processor operator using a standard stenographer's chair.
      F: Lighting effects on humans in various office situations.

   So now what does all this mean ? Getting to the "meat of the coconut", we can come up with some real design and layout considerations. If you were to follow them blindly, you won't be sorry even for one minute. Please don't skim over them, or I might later say "I told you so!" So here are the design and layout considerations broken down into four major parts.

I. Height/distance of equipment support:
   (1) Set keyboard on surface which is 26" above floor.
   (2) Set visual display directly behind keyboard also at 26"
   (3) Set printer on separate surface that's 26 inches high.
   (4) Adjacent writing/reading surface to be 30 inches high.
   (5) Seat height: Allows forearm to be 90-deg to upper arm.
   (6) Angle [subtended from eye] from spacebar to top of screen 60-degrees max. [i.e. limit head movement]
   (7) Set monitor screen about 22 inches from eyes.
   (8) Data reading surface angled vertically and distanced the same as monitor (to your right or left).

II. Miscellaneous support considerations:
   (1) Chair backrest must be firm. Steno chairs have flex joints and thus unacceptable.
   (2) Chairs must have 5 or more castered spider arms.
   (3) Left and/or right desk returns must be [at an angle of 120, not 90, degrees] in respect to front of keyboard.
   (4) Operator's legs must have freedom to swing from left to right, while facing keyboard, without hitting any obstruction.
   (5) All user's data disks and reference manuals must be readily accessible from keyboard operating position (within easy reach).
   (6) Front-to-back desk surface best if at least 24 inches.


If you wish to build yourself one of these desks, capture the above figures by Right Clicking on the image, then Save Picture As [Directory:\Filename on your system]. Print the image from your saved file for a more readable image and working drawing.
III. Illumination considerations:
   (1) General room to be dark except for monitor and an incandescent light or two on either side of keyboard position with the light rays angled away from operator and the visual display screen.
   (2) If fluourescent overhead lighting must be used, then full spectrum tubes (Vita Lites) are acceptable.

IV. Odds and Ends:
   (1) Room wall colors must not be red, orange, dark blue, or purple.
   (2) After two hours at keyboard, take 10-minute break; i.e. walk, stretch, and any other exercising activity.

   Well, there you have it. Ignore the foregoing and your heading for eye strain, back pain, neck pain, and etc.

   The computer desk/work station plan views with their dimensions [shown below] have proved successful for years. Even though they are my designs, please feel free to copy them and enjoy your computing fun (or work) with a healthful ending. The details of the supporting legs are available from the author. [No longer! Marv is now deceased, but desk leg dimensions can be inferred from consideration of the points made in the article. As we have suggested elsewhere, the leg height can be made adjustable. - ed] To date, I have seen no commercially advertised workstations (computer stations), meeting the requirements I have so freely given above, so don't bother looking.

   SPECIAL NOTES: [Set the monitor on the desk surface.] Do not set monitor on top of computer's black box [i.e. CPU]. If easy access to floppy [or removable] drives is desired place to computer on its side [on the desktop. Or, if on the floor angled upward for ready accessibility - ed]. Also, if units are placed as outlined, no special glasses as advertised on TV will be needed.

TOGGLE Editor's Notes:

Are Exact Dimensions Right For Everyone?

   While Marv's ergonomic design experience is a powerful argument for the absolute dimensions he states, they should be taken as a guide, or norm, from which to diverge. The proportions of individual bodies differ enough that some adjustment should be allowed for. Some folks have long torsos and short legs. Others, of the same height, have short torsos and long legs. Some are in-between. Maybe, with a stand-up desk, their overall height determines the height of the desk surface, but what about when they are seated? Surely their heads are at different heights. Seat adjustments must accommodate legs and torsos of different lengths, and desk legs must adjust desk height for comfortable viewing and forearm angle.

Equipment Placement and Head Movement

   Placing the monitor on top of the computer (CPU) case, once a common practice, raises the monitor six or more inches above the desk surface and, often, requires the operator's head to be tilted back to view it. This, when continued over time, can be very tiring because it is not a normal, relaxed position. The seat height, desk height and monitor placement should, preferably, be such that the top of the operator's head is slightly above the top of the monitor and the angle of sight is slightly downward. The keyboard should be about three inches below the desk level.

   The intention of the subtended angle of 60 degrees or less, at the operator's eye, is to ensure that simple eye movement will be sufficient to view the entire screen, and that it will not be necessary for the operator's head to be continually moved up and down to view the monitor--again to avoid fatigue.

EyeGlasses

   If the operator wears bi-focal eyeglasses for normal everyday use, and their use requires tilting the head backward to view the monitor screen, then the fatigue described above will also occur. To avoid having to continually tilt your head to keep the monitor display in focus, two solutions are available: Single lens reading glasses or Trifocal glasses.

   Unless you have special corrective needs, single lens reading glasses of several degrees of magnification can be purchased, quite reasonably, at the drug store. However, if you require bifocals for normal use, this means you that have to switch to single lens glasses when using the computer.

   Trifocals can be procured in which a central lens is designed for viewing the monitor screen, while the upper one is designed for distance viewing, and the lower one for reading or viewing closer objects such as the keyboard or text material. This solution is more expensive, but you don't need to switch glasses when you use the computer.

Foot Rests

   Even while sitting at a desk, a foot rest will relieve tension on the lower back. When a foot rest is not available as a separate item, placement of your foot on one of the chair's castered "spider" arms will serve a similar function, "breaking" the knee and relieving back tension.

   See also Carpal Tunnel Exercises at:
www.toggle.org/html/exercts.htm

  Number 204 - May 2000