Ergonomic Tips (02/02)
It all begins with the chair!
by John R. Chait D.C., drchait@home.com
Member of the Sarasota Personal Computer Users Group, Inc.
In the past the chair has been used to provide both sitting and working comfort for people who work at preset desk heights. This height, twenty-nine inches for PC desk height and twenty-six inches for typewriters, was determined years ago to go well with the physical requirements of the `average' person.
Unfortunately, the result has been the necessity for shorter than average people to raise their chair height as they try to reach a comfortable position at a work surface which is too high for them.
Sitting back in the chair would then result in the person's legs
hanging with their feet off the floor. The person may then experience
pressure under the front of the thigh where it presses against
the chair at an angle. The user is forced to sit forward in the chair to
avoid discomfort because this is a sensitive part of the leg through
which pass many nerve endings and veins.
In fact in any large office with fixed height desks, you will see a large number of shorter individuals, who are forced to sit forward on the chair, away from the support of the chair back. They might as well be sitting on stools.
Employees who are taller than the average person are also affected by the fixed height work surfaces. Though they would more comfortably sit in a higher chair, the work surface would then be too low, causing them to slump forward. So instead they lower their chairs, only to cause other another dilemma. When the person sits back in their lowered chair, their knees will be higher than their behind when their feet are placed flat on the floor, causing all the weight to be on the back of the chair.
Every time this person sits back in his chair, the chair will tilt back. Then every time he wishes to work at his desk, he must move forward in the chair away from the support for his back.
As with the shorter than average individual, this will have an effect on their posture and can cause stress and strain. This can transfer into back pain, fatigue or aggravated tension. In fact; backache is the third most widespread illness in our population. The back pain that develops from the misalignment of the normal posture can be treated very successfully with chiropractic care. Talk to your Chiropractor to find out if there is anything that can be done to correct the ergonomic problem.
The proper means of adjusting a chair for sitting and working comfort is to stand facing the chair and adjust it to a height just below the kneecaps.
Then when you sit back in the chair your thighs will be parallel to
the floor and your weight will be evenly distributed across the chair.
While there are a regrettable number of chairs still being made with
high and prominent arms that prevent the user from sitting properly
positioned at their desk, the trend is towards chairs with recessed or
sloping arms that do not cause this problem. These chairs are highly
recommended.
Once people adjust their chairs to the comfort requirements of their heights, they then will be seated at differing heights relative to their work surfaces, typewriters or keyboards.
If these keys or surfaces are too high, then the users are forced to raise their arms. Many shorter individuals raise their arms from the shoulders, almost like having a constant "shrug". This uses muscles across the top of the shoulders and at the base of the neck, and it often takes very little time before discomfort is felt.
At a properly positioned work surface, keyboard or typewriter, the height of the surface or keys will be at elbow height, when the individual drops his arms to his side while sitting. At this height the person may work in an upright, yet comfortable sitting posture, with the forearms at right angles and parallel to the floor in a relaxed working position.
As you can see, chair positioning is the most important aspect when you consider proper PC use. The problem is your desk is not adjustable and is the limiting factor for your chair adjustment. Hopefully someone will design a desk with an adjustable height so the chair will do what it is supposed to do-support your posture. :
Copyright 2002. This article is from the February 2002 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 1,300+ 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.