In effect, they all refer to the same thing: stress damage to the
bodily tissues which is outstripping recovery. You can think of it as
each day the muscles, tendons, tendon sheaths, ligaments and
so on are stressed by the activities, and then each night the
body repairs them. Up to a point, this stress/recovery
cycle is good for us, it's the same process that gives
fitness in athletes.
With low durations and intensities of stress on the tissues,
the recovery process is completed easily, with time to spare
as it were. Especially when we are young and the body
What happens with overuse is that the repair does not get
completed in time for the next day, and so the stress damage
accumulates. Each day there is a bit more damage that
does not get repaired. The body responds to protect
itself, typically with
swelling and/or pain, and these are signs that must not be
Age is a big factor. As the bodily healing processes inevitably
slow down with age, we can get nearer and nearer to the limit of
our body's healing capabilities, but without noticing. Then when the limit is
reached, symptoms appear because the damage is suddenly
accumulating, and urgent action is needed.
You have to
reduce the amount of stress damage being done each day, so that the body can catch
up. Typically you have to reduce it by a lot.
Fortunately reducing bodily stresses by a lot is often
perfectly achievable, providing you are willing to change some
In general it is long continuous effort by muscles, or
stress repeated all through the day, that is the problem.
Static muscle effort holding a fixed position is particularly difficult, because the
blood flow through the muscle is not assisted by the pumping
action of the muscle expanding and contracting. This is
why getting yourself set up with a low-effort posture is so important when you are at a
computer all day.
Reading glasses are designed to
give you focus at around 40 cm, while distance glasses are
designed to give focus at 6 metres and beyond. A
computer screen is between these, at around
For this reason the DSE regulations provide for free eye
tests to be provided by employers to employees whose job
entails extensive computer use. The Loughborough
University policy is
Your optician is the best source of advice on glasses for
you. In general you should not be looking at your
computer through the bottom half of bifocals or
varifocals, because that will tip your head back.
You should be looking through the middle of the lens, and
glasses are available that have an enlarged central sweet
spot for computer users.
The DSE regulations also provide for your employer to pay
for simple single-vision glasses, if you require them for
that purpose and for no other reason.
If you use reading glasses with a laptop where the screen
is in the same position as a book - low down and close to
you - then that may be alright for you. Ask your
optician, and monitor yourself for signs of fatigue that
may be associated with using your eyes in this way.
The formal advice on how to sit
at a computer is an upright seated posture. If this
does not suit you, for one reason or another, you should
at least make sure that all the various segments of your
body are supported. Then for example you can have a
more open angle at the hip.
The relevant body segments are broadly:
Each segment is attached to the adjacent segment(s) with a
joint and muscle (disc and ligaments in the case of the
spine). By directly supporting each individual
segment - with your chair, armrests, backrest, wrist rest
etc. - you save those joints and muscles from continuous
Also you should keep each joint angle well within its
normal working range, not at one end of its movement.
LCD monitors present relatively
few problems - they are easy to position and do not
flicker. The main thing to watch out for is the size
of the screen in relation to the resolution (number of
dots). In general for desk use you should choose a
screen that is relatively large for its resolution, so
that text and screen items are large and easy to see.
It is possible to have an LCD screen too far away,
depending on its size and resolution, so don't
automatically put it at the back of the desk.
The old style CRT tube monitors can be harder to position
far enough away, and are prone to flicker if not correctly
set up. Also the picture quality deteriorates over
time and most are quite old now.
It is very worthwhile to learn to touch-type, if you
cannot already do so. Touch typing means you don't have to keep looking down at the
keyboard, and this is much better for your neck muscles
because your head stays in balance.
If you regularly type from paper documents, or refer to
paper media while computing, you need a document holder,
and if you can touch type you can position this alongside
the monitor at the same height and distance. This
saves your eyes from having to refocus all the time.
For cost reasons most commercially available
footrests are short, narrow, and high. Some tilt to
an unsuitable angle with
the weight though the heel, and
some have attractive but uncomfortable bumps over the
surface. "Features" are generally misleading.
The effect of all this is to restrict foot movement and raise the feet
too much, with potentially some other sources of discomfort as well.
It is often better to find something yourself, a board or
an old cushion perhaps.
Do some experimentation with books or magazines, for
example, to find the right height, and measure the height,
length and width that you want. Also you should
experiment with the angle - this will vary with the shoes
you wear and how far away you have it.
Chairs: Office chairs are often sold with misleading
claims, and it can be difficult to know which one
is best for you. Here are some tips:
The bottom cushion should not be too
long for you to get fully back in the
seat, with the back of your buttocks
behind the small of your back. This is
often a problem in 'executive' chairs.
Separate height adjustment of the back
is important if it has lumbar support
built in. If the seat has tilt adjustment,
it should be a 'knee tilt' design which
pivots at the front and so limits the change in height at the front
of the cushion.
Armrests should be
height-adjustable if they are fitted.
Fixed-height armrests are nearly always
too low, encouraging you to slump down to
Your chair back should have effective lumbar
(low back) support. It should be
height-adjustable and bulge or curve
forwards slightly, with a soft feel and no
hard edge at the top and bottom.
Add-on back supports are cushions that
attach to the back of seats in order to
provide better support to the lower back.
Armrests must be at the correct height
for the user. Too high and the user will
tend to work with their shoulders hunched.
Too low and the users will slouch in their
seat. Most fixed armrests are set too low,
so adjustability is more or less
essential. If you need to you may be able
to build up the height of fixed armrests
by wrapping foam around them; if not it is
better to remove them. They can
nearly always be unbolted from underneath.
Armrests must be short enough to allow
the chair to get close enough to the desk.
This is generally little more than half
the length of the bottom-cushion.
Not everyone likes armrests, but those
who do can benefit from the reduction in
arm weight hanging from the shoulder. This
also reduces the static loads on the spine and
The cushion should be flat. Avoid
cushions which have a rise at the back as
these will compress the buttocks, also
avoid 'waterfall front ' seats which have
an extended slope at the front - these
give no support but can prevent you
sitting fully back in the seat.
Ideally the seat-back should have a smooth
lumbar support curve which is at least 25
cm in vertical length, and be adjustable for height. Choose a shape which
is simple and spreads support over the
largest possible area, to reduce pressure
on the skin. If a chair lacks this but is otherwise suitable, you could use an add-on
lumbar support. You don't need lateral support in an office chair.
One of the ways cheap chairs are made
cheaply is by using low-density
foam in a thin layer. Check this by
pressing your fist hard into the cushion
and backrest. If your knuckles easily
'bottom out' onto the hard surface
underneath, the foam won't last.