To: apa@CS.CMU.EDU, bovik+@CS.CMU.EDU
Reply-to: Tim Freeman <tsf@CS.CMU.EDU>
Subject: Carpal Tunnel Syndrome
Date: Wed, 28 Aug 91 15:47:21 -0400
Message-ID: <8839.683408841@U.ERGO.CS.CMU.EDU>
From: Timothy_Freeman@U.ERGO.CS.CMU.EDU

I fetched this article by sending "GET CTS SHEEHA_M" to
listserv%bitnic.bitnet@vma.cc.cmu.edu. 

"Avoiding carpal tunnel syndrome: A guide for computer keyboard users,"
University Computing Times, July-August 1990, pp. 17-19. Author: Mark
Sheehan, University Computing Services, Indiana University, Bloomington,
IN 47405. BITNET: Sheehan@IUBACS.
 
 
Carpal tunnel syndrome (CTS) is a painful, debilitating condition. It
involves the median nerve and the flexor tendons that extend from the
forearm into the hand through a "tunnel" made up of the wrist bones, or
carpals, and the transverse carpal ligament (Figure 1). As you move your
hand and fingers, the flexor tendons rub against the sides of the tunnel.
This rubbing can cause irritation of the tendons, causing them to swell.
When the tendons swell they apply pressure to the median nerve. The
result can be tingling, numbness, and eventually debilitating pain.
 
 
[Figure 1 goes here]
 
 
CTS affects workers in many fields. It is common among draftsmen,
meatcutters, secretaries, musicians, assembly-line workers, computer
users, automotive repair workers, and many others. CTS can be treated
with steroids, anti-inflammatories, or physical therapy, or with surgery
to loosen the transverse carpal ligament. Recovery of wrist and hand
function is often, but not always, complete.
 
Causes
 
Like many skeletomuscular disorders, CTS has a variety of causes. It is
most often the result of a combination of factors. Among these are:
 
Genetic predisposition. Certain people are more likely than others to
get CTS. The amount of natural lubrication of the flexor tendons varies
from person to person. The less lubrication, the more likely is CTS. One
study has related the cross-sectional shape of the wrist, and the
associated geometry of the carpal tunnel, to CTS. Certain tunnel
geometries are more susceptible to tendon irritation.
 
Health and lifestyle. People with diabetes, gout, and rheumatoid
arthritis are more prone than others to develop CTS, as are those
experiencing the hormonal changes related to pregnancy, menopause, and
the use of birth control pills. Job stress has also been linked to an
increased likelihood of CTS. And CTS seems to be more frequent among
alcoholics.
 
Repetitive motion. The most common cause of CTS that's been
attributed to the workplace is repetitive motion. When you flex your hand
or fingers the flexor tendons rub against the walls of the carpal tunnel. If
you allow your hand time to recover, this rubbing is not likely to lead to
irritation. The amount of recovery time you need varies from fractions of
a second to minutes, depending on many circumstances, including the
genetic and health factors mentioned above, as well as the intensity of
the flexing, the weight of any objects in your hand, and the extent to
which you bend your wrist during flexing.
 
Trauma. A blow to the wrist or forearm can make the tendons swell and
cause or encourage the onset of CTS.
 
 
Prevention
 
Computer keyboard users can take several steps to lower their chances of
developing CTS. Some of these center around the configuration of the
workplace, or "ergonomics." Others have to do with human factors.
 
Ergonomics. Proper seating is crucial to good ergonomics. The height of
your seat and the position of your backrest should be adjustable. The chair
should be on wheels so you can move it easily. Arm rests on the chair,
though optional, are often helpful.
 
Figure 2 illustrates many of the points discussed below.
 
 
                         [Figure 2 goes here]
 
 
 
Table height. To adjust the chair properly, look first at the height of the
table or desk surface on which your keyboard rests. On the average, a
height of 27-29 inches above the floor is recommended. Taller people will
prefer slightly higher tables than do shorter people. If you can adjust your
table, set your waist angle (see below) at 90, then adjust your table so
that your elbow makes a  90 angle when your hands are on the keyboard.
 
Wrist angle. If your keyboard is positioned properly your wrists should
be able to rest comfortably on the table in front of it. Some keyboards are
so "thick" that they require you to bend your hands uncomfortably upward
to reach the keys. If so, it will help to place a raised wrist rest on the
table in front of the keyboard. A keyboard that requires you to bend your
wrists is a common cause of CTS among computer users.
 
Elbow angle. With your hands resting comfortably at the keyboard and
your upper arms vertical, measure the angle between your forearm and
your upper arm (the elbow angle). If it is less than 90, raise the seat of
your chair. If the angle is greater than 90, lower the seat. Try to hold
your elbows close to your sides to help minimize "ulnar displacement" 
the sideways bending of the wrist (as when reaching for the "Z" key).
 
Waist angle. With your elbow angle at 90, measure the angle between
your upper legs and your spine (the waist angle). This too should be about
90. If it is less than 90, your chair may be too low (and your knees too
high). Otherwise, you may need to alter the position of the backrest or
adjust your own posture (nothing provides better support than sitting up
straight). (Note: If making your waist angle 90* changes your elbow angle,
you may need to readjust the height of your chair or table.)
 
Feet. With your elbows and waist at 90 angles, your feet should rest
comfortably flat on the floor. If they don't, adjust your chair and table
height and repeat the steps above. If your table isn't adjustable and your
feet don't conmfortably reach the floor, a raised footrest can help.
Otherwise, you may need a different table.
 
Work routine
 
You need very little recovery time between keystrokes to cool and
lubricate the flexor tendons. If you type constantly, however, the need for
recovery builds. Further, working with your hands bent upward at the
wrists or frequently bending your wrists sideways heightens the friction
within the carpal tunnel. It takes longer to recover from these motions.
Working under stress (deadline pressure, anger, or other anxiety) can make
matters even worse.
 
Many studies recommend a 10-15 minute break each hour to give yourself
the recovery time you need. This needn't be a break from productive
activities -- just a break from your keyboard. Exercises can help, too. Try
the following:
 
    a)Make tight fists, hold for one second, then stretch your fingers
out wide and hold for five seconds. Repeat several times.
 
    b)With arms outstretched in front of you, raise and lower your
hands several times.  Rotate your hands ten times (make
circles in the air with the fingertips).
 
Variety is the key. CTS occurs most frequently in workers whose motions
are not only repetitious but are kept up for hours at a time. If you use a
keyboard, structure your workdays to include a mix of activities each
hour. For example, instead of typing all morning and filing all afternoon,
mix typing and filing throughout the day.
 
Early detection
 
The most painful cases of CTS are those that have gone undetected or
untreated over a long time. CTS can be caught easily in its early stages,
however, and much of the pain and all of the disability avoided.
 
Early symptoms include a tingling in the fingers, often beginning several
hours after work activity has stopped. Because of this delay in the
appearance of symptoms, many CTS sufferers don't make the connection
between their work activities and the pain they feel until it's too late. The
tingling can lead, over time, to stiffness and numbness in the fingers and
hand, and then to severe wrist and hand pain.
 
For many individuals the early symptoms of CTS go unnoticed. Employers
and coworkers can help one another identify the onset of CTS by watching
for and pointing out any unconscious shaking of the hands, rubbing of the
wrists, or unusual postures or hand positions at the keyboard.
 
At the first sign of CTS, you should be examined by a doctor who
specializes in hand and wrist disorders. The doctor can perform a number
of simple tests to detect CTS, and can prescribe specific steps for
avoiding the problem.
 
Summary
 
Carpal tunnel syndrome is common among computer keyboard users. It can
strike anyone, and its consequences are serious. Awareness of the problem
and its causes is crucial to preventing CTS. With proper ergonomics and
attention to the work routine you can prevent CTS; with early detection
and treatment it need never become debilitating. The employer's attention
to stress levels, proper ergonomics, and the early warning signs of CTS
are important in keeping the ailment at bay in the workplace.
                __________________________________
 
A note on retrieving the figures:
 
1. Open an FTP session to the UCS FTP server, IP address 129. 79. 16.96.
2. Log in with any (or nul) username and password.
3. Issue the command "cwd ucspubs" to get to the UCS publications
directory.
4. Issue the commands "get hand.hqx" and "get ergonomics.hqx" to transfer
those files to your account.
5. Use a hexbin utility such as that in Stuffit to convert the files from
hexadecimal to binary. They are in MacDraw ll format.
 
*************************************************************
CCNEWS Copyright Notice
 
If you use this article, in whole or in part, in printed or
electronic form, you are legally and morally obligated to
credit the author and the original publication name, date,
and page(s). We suggest that you also inform the author of
your intention to use this article, in case there are updates
or corrections that he or she might wish to suggest.
 
The ideas and opinions expressed in this article, as well as
articles obtained through CCNEWS and the CCNEWS Articles
Archive, do not necessarily reflect those of EDUCOM. EDUCOM
will not accept responsibility for misinformation, nor will
EDUCOM be responsible for misuse of information obtained
through the CCNEWS Articles Archive.
 
If space and format permit, we would appreciate your
crediting the "Articles database of CCNEWS, the Electronic
Forum for Campus Computing Newsletter Editors, a BITNET-based
service of EDUCOM." We would also appreciate your informing
us (via e-mail to CCNEWS@EDUCOM) when you use an article, so
we will know which articles have proven most useful.
 
*************************************************************