Ergonomics and The Computer User
Why Is It Important?
The personal computer is rapidly becoming a common household item and is now a necessary tool for all small businesses. There is a growing segment of the population that uses the computer exclusively for its vocation and it is in this group that we have begun to see the physical effects of spending long hours day after day at the computer. With improvements in technology the computer users are positioned to perform more and more functions without leaving their workstation. The physical effects of this trend are that the users are prone to the effects of postural stress.
We have come to realize in the high tech world that low force tasks involving high repetition and long duration have negative effects on the body. In jobs requiring computer work the users are faced with high pressure working conditions so they tend to ignore or at least tolerate the signs brought on by the cumulative trauma created by the work. The user may only take a break after the project is finished and there is permanent damage.
This process goes on day after day, year after year. Over half of computer users complain of neck or back pain. From here the effects may have psychological and physical consequences that over time may translate into permanent debilitating health conditions affecting other parts of the body.
Carpal Tunnel Syndrome
For example, we are observing an alarming incidence of Carpal Tunnel Syndrome. The condition begins with chronic irritation of the soft tissues in the wrists leading to the shoulders. The resulting warning signs if left ignored lead to the formation of scar tissue and nerve impingement in the hands. The hands become numb and begin to lose muscle function. If left uncorrected the condition will lead to permanent damage and subsequent loss of muscle control of the hands. If the condition is not treated or addressed early enough computer users face the prospect of surgery as the only hope.
With surgery the probability is high for computer users to suffer from a recurrence of the condition if they return to computer work. The experts are beginning to realize that the only real answer to the problem lies in prevention. In order to perform physical activities that are highly repetitious attention and application to specific ergonomic principals are required. Whether working at the computer for livelihood or enjoyment just by implementing some of these principles efficiency and productivity will increase.
Supporting the Spine While Seated
Working from a sitting position can generate strain on the body as the spine is taken out of its neutral position for extended periods of time. By supporting a healthy posture these strains are reduced or eliminated. Having an ergonomic chair with an adequate lumbar support or adding a support to an existing chair the user will maintain the natural curvature of the low back.
The neck normally is positioned so that it curves toward the front. As we look in a downward position, the neck or cervical spine straightens or begins curving in a reverse direction resulting in neck, shoulder and upper back pain. In order to avoid this situation the top of the monitor should be kept at approximately eye level or slightly below.
When chairs are positioned too far back from the screen or keyboard there is a tendency to bring the head forward in order to view the screen. At the same time there is a tendency to lean forward in the seat thereby losing contact with the seat back. As a result pressure on the lower spine is increased dramatically. The best way to avoid contorting the posture in order to comfortably view the screen is to use a monitor that is at least 19 inches in size and at arms length from the user.
Chair backrests should mold to the natural configuration of the spine and have tilt, horizontal and vertical adjustments. The seat pan of the chair should have sufficient depth and width, sufficient padding and a waterfall curvature at the front. The seat pan height should be adjustable so the feet are able to rest firmly on the floor without excessive pressure on the back of the thighs.
The user should have the option of using a footrests with an incline and height adjustment.
Chair armrests should have angle and width adjustability so they do not interfere with the natural movement of the arms while keyboarding. The armrests should have sufficient padding and height adjustability so they provide for comfortable resting of the arms and forearms during breaks. In this way static muscle tension of the shoulders down to the wrists is reduced and frequent resting breaks are encouraged.
There is also a tendency to bring the shoulders forward in order to reach the keyboard adding to the strain of the shoulder and mid-back muscles. The solution is to have a chair that can be brought forward enough to avoid this unnatural posture. The armrests should not interfere with this forward positioning of the chair. It is desired to have the ear over the shoulders and the shoulders brought back over the rib cage while sitting.
Shoulder and mid-back strain is avoided by having the keyboard relatively close to the body without having to lean forward creating a gap between the back and seat back. This can be achieved by using floating monitor and keyboard stands that utilize dynamic mechanical arms which support the keyboard as well as the mouse. Of course the low back or lumbar spine has a natural forward curve and a proper chair should have a proper lumbar support to maintain that curve.
Supporting the Wrist and Forearm
With the wrists in line with the hands and unrestrained along with the forearms and arms we can avoid problems like tendonitis that are common today among computer users. In this way the hands are move as a unit without having to reach for keys with the fingers. The idea is to take mini-breaks throughout the day and allow the hands and wrists to relax between episodes of typing. This is done by using various devices or pads that help support the wrist and forearms.
Due to the close proximity of the hands relative to the distance between the elbows, the forearms are angled inward when using a regularly designed keyboard. This situation forces hands to deviate laterally (ulnar deviation) in order to maintain a parallel position while typing. By using a keyboard with a split center this deviation is unnecessary.
There is one keyboard on the market that eliminates awkward hand positioning and greatly reduces the forces associated with keyboarding. The Datahand Keyboard is an innovative solution to the limitations of a traditional keyboard.
Finally, we must remember that eyestrain or Computer Vision Syndrome (CVS) is a major source of fatigue. Glare on the screen is a major culprit and should be avoided or eliminated by using a glare filter, by avoiding a direct light source on the screen, and by maintaining relatively low ambient light.
1) Allie, Paul. Conference Paper. “Supporting Natural Human Motion While Seated”
2) Inkeles, Gordon and Iris Schencke. Ergonomic Living: How to Create a User-Friendly Home and Office. New York: Simon and Schuster, Inc., 1994
3) Kroemer K. H. E. and E. Grandjean. “The Design of Workstations.” Fitting the Task to the Human: A Textbook of Occupational Ergonomics. London: Taylor and Francis, 1997
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