Where will the computer be used? Think about the following environmental
conditions where the computer will be used:
- Lighting - make sure that the lighting isn't too bright. You
shouldn't see any bright light glare on the computer screen. If you do,
move the screen, lower the light level, use a good quality, glass anti-glare
screen. Also make sure that the computer monitor screen isn't backed to
a bright window or facing a bright window so that there's the screen looks
washed out (use a shade or drapes to control window brightness).
- Ventilation - make sure that you use your computer somewhere
that has adequate fresh-air ventilation and that has adequate heating or
cooling so that you feel comfortable when you're working.
- Noise - noise can cause stress and that tenses your muscles
which can increase injury risks. Try to choose a quiet place for your workstation,
and use low volume music, preferably light classical, to mask the hum of
any fans or other sound sources.
- Take a break! All Ergonomists agree that it's a good idea to
take frequent, brief rest breaks: Practice the following:
- Eye breaks - looking at a computer screen for a while causes
some changes in how the eyes work, causes you to blink less often, and
exposes more of the eye surface to the air. Every 15 minutes you should
briefly look away from the screen for a minute or two to a more distant
scene, preferably something more that 20 feet away. This lets the muscles
inside the eye relax. Also, blink your eyes rapidly for a few seconds.
This refreshes the tear film and clears dust from the eye surface.
- Micro-breaks - most typing is done in bursts rather than continuously.
Between these bursts of activity you should rest your hands in a relaxed,
flat, straight posture. During a micro-break (< 2minutes) you can briefly
stretch, stand up, move around, or do a different work task e.g. make a
phone call). A micro-break isn't necessarily a break from work, but it's a
break from the use of a particular set of muscles that's doing most of the
work (e.g. the finger flexors if you're doing a lot of typing).
- Rest breaks - every 30 to 60 minutes you should take a brief
rest break. During this break stand up, move around and do something else.
Go and get a drink of water, soda, tea, coffee or whatever. This allows
you to rest and exercise different muscles and you'll feel less tired.
- Exercise breaks - there are many stretching and gentle exercises
that you can do to help relieve muscle fatigue. You should do these every
1-2 hours.
- Ergonomic software - working at a computer can be hypnotic, and
often you don't realize how long you've been working and how much you've
been typing and mousing. You can get excellent ergonomic software that you
can install on your computer. The best software will run in the background
and it will monitor how much you've been using the computer. It will prompt
you to take a rest break at appropriate intervals, and it will suggest
simple exercises.
- What about ergonomic gizmos? These days just about everything
is labeled as being "ergonomically designed" and much of the
time this isn't true and these so-called ergonomic products can make things
worse. If you're thinking about buying an "ergonomic product"
as yourself the following 4 questions:
- Does the product design and the manufacturer's claims make sense?
- What research evidence can the manufacturer provide to support their
claims? Be suspicious of products that haven't been studied by researchers.
- Does it feel comfortable to use the product for a long period? Some
ergonomic products may feel strange or slightly uncomfortable at first
because they often produce a change in your posture that's beneficial in
the long-term. Think of some products as being like new shoes that
initially may feel strange but then feel comfortable after being used for
a while. If a product continues to feel uncomfortable after a reasonable
trail period (say at least a week) time then
stop using it.
- What do ergonomics experts say about the product? If they don't recommend
it don't use it.
There are many computer-related "ergonomic" products, the most
common ones being:
- "ergonomic" keyboards - most of these are keyboards
where the alphanumeric keys are split at an angle. For a non-touch typist
this design can be a disaster! The split design only addresses issues of
hand ulnar deviation, and research studies show that vertical hand posture
(wrist extension) is more important. There is no consistent research evidence
that most of the split-keyboard designs currently available really produce
any substantial postural benefits. For most people a regular keyboard design
works just fine if it's put in the proper
neutral position.
- "ergonomic" mice - many of these mouse designs or
alternative input device designs can work well to improve your hand/wrist
posture. However, it's important to check that you can use these with your
upper arm relaxed and as close to your body as possible. Overreaching to
an "ergonomic mouse" defeats any benefits of this design. Check
out the 10 tips for using a computer mouse.
- Wrist rests - these were very popular a few years ago, but research
studies haven't demonstrated any substantial benefits for wrist rests. In
fact, a wrist rest can actually increase pressure inside the carpal
tunnel by compressing the undersurface of the wrist (take a look at
your wrist and you'll probably see blood vessels that shouldn't be
compressed!). Studies by Dr.
David Rempel at the University of Berkeley, California, show that
pressure applied to the underside of the carpal tunnel is transferred
into the tunnel itself via the transverse carpal ligament and that
intracarpal pressure doubles with a wrist rest compared with floating
the hands over a keyboard. If you choose to use a wrist rest, using
one with a broad, flat, firm surface design works
best, and rest the heel of your palm on this NOT your wrist. Try not
to rest while you're actually typing, but rest in between bursts of
typing movements. Avoid soft and squishy wrist rests because these will contour to your wrist,
restrict the freedom of movement of your hands, and encourage
more lateral deviation during typing. Look at the surface of a typical
wrist rest that's been used and you'll see that it gets eroded away,
which means that the user has been sliding their wrists over the
surface which also compresses the blood vessels often visible at the
wrist. Remember, your hands should be able to glide
above the surface of a wrist rest during typing, don't lock them in
place on the rest while you type.
- Support braces/gloves - There is no consistent research evidence
that wearing wrist supports during computer use actually helps reduce the
risk of injury. If you do like wearing a wrist support make sure that it
keeps your hand flat and straight, not bent upwards. There is some evidence
that wearing wrist supports at night in bed can help relieve symptoms for
those with carpal tunnel syndrome.
- Forearm supports/resting forearms on chair arms - Generally
it's not necessary, nor a good idea, to rest the forearms on any support
while typing because of the potential for restriction of circulation to
the finger flexor muscles in the forearm and compression of the ulnar
nerve at the elbow. If the keyboard/mouse are appropriately arranged
they should be accessible with the user's arms in a neutral position
(close by the body and with the upper arm hanging in a relaxed way)
which does not pose any significant neck or shoulder load. If forearm
supports are required it is usually a sign of a poor ergonomic
arrangement.
- Sit-stand Workstations -
the use of a height adjustable worksurface for sitting and standing
work is becoming fashionable. However, there is scant evidence that
sit-stand furniture has cost effective benefits. The evidence suggests
that there may be a reduction in back discomfort, but the research for
this has not used adequate comparison groups (e.g. testing people who
stand for the same time at the same frequency without doing
keyboard/mouse work). There is no evidence that sit-stand improves
wrist posture when keying or mousing. Logically, the real benefit of
sit-stand is just that, changing between sitting and standing. But
standing in a static posture is even more tiring than sitting in a
static posture, so movement is important. We recommend that the most
cost effective way to obtain the benefits from sitting and standing is
for people to sit in a neutral work posture and then intermittently to
stand and move around doing other things, like filing papers, making
phone calls, getting coffee, making photocopies etc.) rather than
trying to keyboard or use a mouse while standing.
Recent research suggests that electronic sit-stand workstations, that
can be quickly adjusted, allow each worker to modify the height of their
worksurface throughout the day, and this may reduce musculoskeletal
discomfort and improve work performance.
- Height
adjustable, split worksurfaces - with respect to wrist
posture, the issues are the same for height adjustable, split
worksurfaces and sit-stand worksurfaces:
- If the surface is too low the hand will be in greater extension
- If the surface is too high the elbow will be in sustained
flexion
- If it's a flat surface then it's just the same argument as is
used above for a negative-slope keyboard tray arrangement.
You can't set a flat worksurface at an appropriate height for the 5
main tasks of office work - keyboarding, mousing, writing, viewing
documents and viewing the screen- these all require different heights
for an optimal arrangement. A negative-slope keyboard tray
system serves as the height and angle adjustment mechanism for the
keyboard, and the mouse platform serves as the height and angle
adjustment for the mouse when attached to a worksurface that is set
for writing height. Monitor height is best adjusted by a separate
monitor pedestal rather than trying to move a whole worksurface. There
are a number of new split worksurface designs that may work quite well
to achieve optimal monitor positioning.
The above 10 steps give a brief summary of good ergonomic design practice
for computer workstations, but there's lots more to consider. You can read
about ergonomics in many books, you can browse other materials on this CUErgo web site, you can get information from
the Human Factors and Ergonomics Society. You can
use the Computer Workstation Checklist to help
to identify problems, and you can ask expert
Ergonomists
for help and advice.
Also, see the 'Computer
Workstation summary'
diagram created by the DEA651 class of 2000.
If you have any questions or comments about the information on this page
or this web site you can send these to Professor
Alan Hedge at Cornell University.
For more detailed information and exercises you can also check out the free 'HealthyComputing.com'
web site.
Happy computing!
This guide is translated into
Serbo-Croatian by Jovana Milutinovich from Geeks Education.
people have visited this page.
<Home
Note that all materials on this page and web site are
copyright and may only be copied or distributed for nonprofit educational
purposes without permission.
© Alan Hedge, page content last revised on
October 17, 2012
