Sarasota PC Monitor
Ergonomic Tips (12/02)
The keyboard: friend or foe?
by John R. Chait D.C., drchait@home.com
Member of the Sarasota Personal Computer Users Group, Inc.People are always being told about how typing for long periods of time is bad for you, but have you ever wondered what really happens and if there is a real cause for alarm? Unfortunately there is! Poor typing posture can cause pain and other symptoms in adults as well as children.
Low Back Pain
The lifetime prevalence of low back pain has been estimated at nearly 70% for industrialized countries (Anderson, 1991), and much of this is related to poor posture while sitting. Back pain is certainly not limited to adults. In fact, it has been reported that approximately 23% of elementary school children complain of backache and that this percentage rises to about 33% among the secondary school population (Mierau, 1984, cited in Marschall, Harrington, and Steele, 1995). Two European studies even found that as many as 60% of schoolchildren experience back problems by the ages of 15 or 16 (Balague, 1988 and Davoine, 1991, both cited in Mandal, 1997). A study of 500 US teenagers found that 56% of the males and 30% of the females suffered from degeneration of the spine as supported by X-ray evidence (Fish, 1984, cited in Knight and Noyes, 1999).
Hand/Wrist Problems
These include Cumulative Trauma Disorders, better known as CTDs, RSIs (Repetitive Stress Injuries), OODs (Occupational Overuse Disorders), etc. Since the late 1980s, the incidence of CTDs has skyrocketed, especially among that performing computer intensive work. The number of repeated trauma cases increased steadily from 23,800 in 1972 to 332,000 in 1994-a 14-fold increase (Bureau of Labor Statistics, 1995).
Although there are few statistics on children and CTDs, with so many children starting to use computers at such an early age, there is no telling whether this may accelerate the incidence of CTDs. Since the average American child is currently spending one to three hours daily in front of a computer (Roper Starch, 1999), there is a great potential for injury. In their milder forms, CTDs may involve injury to the tendons and their sheaths within the hand and wrist area, which may cause:
Discomfort
Tenderness to touch
Inflammation
Weakening of the tendons
The more serious CTDs may lead to the following symptoms in the hands, fingers, and arms:
Pain
Numbness
Tingling
Loss of sensation
Carpal Tunnel Syndrome (CTS)
Carpal Tunnel Syndrome (CTS)
Carpal Tunnel Syndrome (CTS) is one of the most serious and best known CTDs. It results when the median nerve does not "work" properly. Usually, this is thought to occur because there is too much pressure on the nerve as it runs into the wrist through an opening called the carpal tunnel.
Eventually, the pressure inside the tunnel reaches a point when the nerve can no longer function normally. Pain and numbness in the hand begin and progress if the cause is not eliminated. Repeated forceful movements made by the hands while in deviated postures (flexion, extension, ulnar radiation, and radial radiation) are known to dramatically increase the risks of developing this syndrome.
Ulnar and radial deviations contribute to CTDs, but it is flexion and, particularly, extension that are the real culprits. Remember that when the wrist is in a neutral position, the carpal tunnel is as large as it can be so the nerve has as much room as possible and injury can be prevented.
Preventing Injury
When it comes to preventing injury, adults and children need to use the following rules:
* Keep their body and wrist posture in neutral positions while sitting and keyboarding.
* Have an appropriate PC configuration.
* Take breaks at appropriate intervals.
* Neutral Keyboarding Posture
* Upper and lower back well supported by chair
* Chair height set so that the chair seat does not compress the back of the knees
* Feet firmly planted on a surface for support (floor or footrest)
* Head balanced on neck (not tilted back or too far forward)
* Upper arms close to body and relaxed (not abducted to the side or flexed forward)
Sitting so that the:
* Angle formed by the shoulders, hips, and knees is >90 degrees
* Angle formed by the shoulder, elbow, and wrist is >90 degrees
* Angle formed by the hips, knees, and feet is >90 degrees
* Wrists at a neutral position, level with forearm (<15 degrees deviation)
* Chair armrests not directly compressing any part of the forearms or elbows
Moving a mouse with your forearm and not just your wrist will reduce hand deviation. If you suspect you have an injury, get it checked by a professional. :
Copyright 2002. This article is from the December 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.
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