|
While talking
about a safe and productive computer workstation, the topic of a
well-designed and appropriated-adjusted chair comes to our mind
naturally. Being an inevitable part of a good workstation, chair offers
essential support to the back, legs, buttocks, and arms, along with
reducing exposures to awkward postures, contact stress, and forceful
exertions. The advantages of using a chair with increased adjustability
include ensuring a better fit for the user, providing sufficient
support in a variety of sitting postures, and allowing variety of
convenient sitting positions throughout the workday. If more than one
person is using the chair per day, these points have more relevance.
Before selecting a particular chair, try out different ones and
finalize on the one that gives the best support. To ensure that the
chair will provide adequate support, it is important that you try out
different chairs before purchasing one. To create a safe and dynamic
workstation, the following parts of the chair have to be observed in
detail before selection.
o Backrest
o Seat
o Armrest
o Base
The chair should be adjusted while placing the monitor, keyboard and
desk in your workstation.
Chair
Guidelines
o Ensure that the
backrest of your chair corresponds to the natural curvature of your
spine providing enough support to the lumbar region.
o Ensure that the
seats of your chair are comfortable enough to allow your feet to rest
flat on the floor or footrest.
o Ensure that the
armrests of your chair are soft allowing your shoulders to relax and
elbows to stay close to your body.
o Ensure that your
chair has a five-leg base with rollers that allow it to move easily on
the floor.
Backrest
of the chair
Probable
Risks
If the backrest of
the chair is not designed properly with inadequate size, material, and
positioning, the back support will not be sufficient. This would lead
to inappropriate postures that cause back pain and fatigue. A chair
without suitable or appropriate backrest will fail in supporting your
lumbar spine and won.t maintain
the natural S-shape curvature of the spine.
Fig.
14 . The
backrest position
Feasible
Solutions
o
Roll up a towel at
the lumbar region or place a removable back support cushion for a
temporary support if the chair that you use currently doesn’t provide a
good lumbar support. This would help you maintain the natural curve of
the spine.
o You can try using
a chair with easily adjustable backrest and which supports the back in
all your convenient seating postures. A backrest should have the
following features:
- The
backrest should have a good lumbar support with adjustable height
options for fitting the lower back in different postures. Ensure that
the outward curve of the backrest should fit into the small of the
back.
2.
The backrest should have an adjustment that allows the user to recline
at least 15 degrees from the vertical. The backrest should lock in
place or be tension adjustable so that adequate resistance is ensured
to the lower back movement.
- Shorter
users can sit with their backs against the backrest without worrying
about their knees touching the front edge of the seat pan with the help
of a device that enables to move forward and backward. Taller users can
sit with their backs against the backrest while supporting their thighs
and buttocks fully.
Probable
Risks
Too high chairs
force the users to work with their feet unsupported and make them move
forward in the chair to a position where the back gets zero support
which makes it even more difficult for them to maintain the S-shape of
the spine. If the user sits continuously in such postures, it can cause
fatigue, restricted circulation, swelling, numbness, and pain.
Feasible
Solutions
o
Do make use of a
footrest that gives good support to the feet if your seat cannot be
lowered.
o The seat pan of
your chair should be adjustable and of appropriate size to provide
support to your body in all your convenient postures. See to it that
the seat has the following features:
i. The height of the
seat should be adjustable especially when there are multiple users. It
is ideal if the entire sole of the user’s feet can be rested on the
floor with the back portion of the knee slightly higher that the seat
of the chair.
ii. The seat has
padded and a rounded, "waterfall" edge.
iii. The width of the
seat should accommodate almost all the hip sizes, at least the
majority. For larger users, those with oversize seat pans should be
provided.
Probable
Risks
It is very
uncomfortable for the user to sit in a seat pan that is inappropriately
sized. It fails to give enough support to the legs and restrict the
whole body movements of the user. Shorter ones place more pressure on
the buttocks of the taller users and longer ones place more pressure on
the knees of the shorter users minimizing the back support. One that is
too small can restrict movement and provide inadequate support.
Prolonged use can restrict blood flow to the legs and create irritation
and pain.
Feasible
Solutions
o The depth of the
seat pan should be adjustable to support taller users adequately
simultaneously allowing shorter users to sit with full support to their
back. It should also provide support for most of the thigh without
contact between the back of the user’s knee and the front edge of the
seat pan.
o Always use a
footrest, which elevates the knee slightly to relieve pressure on the
back of the leg.
o Use a chair that
is sized to fit small or large users. This is very important if
multiple users share the chair.
Probable
Risks
Most users tend to sit in awkward postures and thus lack adequate
support, if the armrests they use are not adjustable. Let’s discuss the
negative points of such armrests:
o Armrests that are
too low force you to lean over to the side to rest one forearm which in
turn results in uneven and awkward postures, fatiguing the neck,
shoulders, and back.
o Armrests that are
too high force you to sit with raised shoulders resulting in muscle
tension and fatigue in the neck and shoulders.
o Armrests that are
too wide force you to reach with the elbow and bend forward for
support. This results in pulling the arm from the body and leads to
muscle fatigue in the shoulders and neck.
o Armrests that are
too close restrict movement in and out of the chair.
o Armrests that are
too large or inappropriately placed may interfere with the positioning
of the chair. If the chair cannot be placed close enough to the
keyboard, you may have to reach and lean forward in your chair. This in
turn leads to fatigue and strain the lower back, arm, and shoulder.
o Armrests that are
made of hard materials or that have sharp corners can irritate the
nerves and blood vessels located in the forearm. This will create pain
or tingling in the fingers, hand, and arm.
Feasible
Solutions
Learn more about Healthy Computing habits.
Some chairs come
with armrests that give more discomfort that comfort while working on
the computer. Some interfere with your workstation and some others
cannot be adjusted properly. Try removing such armrests or at least
stop using such armrests. While selecting chairs with armrests, check
whether they can be adjusted according to your postures so that they
give good support to your lower arm while allowing the upper arm to be
close to the body. Armrests that can be properly adjusted should have
the following features:
o They should have
ample width for the users to get in and get out of the chair easily.
o They should be
close enough to support your lower arms keeping your upper arms close
to your torso.
o They should be
low enough keeping your shoulders relaxed while working on the
computer.
o They should be
high enough to support your lower arms when positioned comfortably at
your sides. If the armrests are too low and you find it difficult to
adjust them, add padding to the top of the armrests.
o They should be
large enough to support most of your lower arm. Moreover, ensure that
they are small so that they do not interfere with your chair
positioning.
o Ensure that the
armrests are made of soft material and have blunt edges.
It is not necessary that all users should keep armrests to their
chairs. It depends on the amount of hours the user spends on the system
per day, whether the user has suffered from or is suffering from
musculoskeletal disorder (MSD), or whether the user prefers to work
with armrests on the chair. But, if you have already decided to have a
pair for your chair, do consider all the above-mentioned points before
selecting the product.
Probable
Risks
o If the number of
legs of your chair are four or less than four, the support and balance
it gives the user will be lesser and hence there are chances of the
chair bending and hence the user falling down.
o If the casters
used for the chair are not good or if the chair doesn’t have casters,
the user might find it difficult to position the chair with respect to
the desk. Inappropriate choice of casters, or a chair without casters,
can make positioning the chair in relation to the desk difficult. This
may result in the user bending to access the different components that
in turn might lead to muscular strain and fatigue.
Feasible
Solutions
o Ensure that your
chair has a strong, five-legged base.
o The casters of
the chair should go with the flooring of the workstation. Do ensure
that the casters of your chair are proper enough.
Chair
Recipe
- The
chair that you select for your workstation should be easily adjustable.
- Ensure
that your chair has a strong base with five legs with casters that are
good enough to roll over the floor or carpet.
3.
The chair should revolve 360 degrees sot that the user can access items
around the workstation without twisting and straining.
- It
is recommended that the height of the seat is at least 16 inches.
- The
length of the seat pan should be between 15 inches and 17 inches.
- The
width of the seat pan should be at least 18 inches. It should have
ample room for the user’s thighs.
- The
edges of the chair should be padded and shaped with soft, but firm
material for good support.
- It
is recommended that the minimum adjustable tilt of the seat pan should
be in the range of 5 degrees, both forward and backward.
- Try
to avoid extremely contoured seats because they restrict different
convenient sitting postures and are uncomfortable for many users.
- Ensure
that the front edge of the seat pan is rounded in a .waterfall. fashion.
- Check
whether the material used for the seat pan and back is firm,
breathable, and resilient.
- The
depth of the seat pan should be adjustable. Do not go for chairs in
which only the back can be tilted forward and backward because they
don’t provide adequate adjustment for multiple users. There are chairs
with seat pans that can slide forward and backward and have a fixed
back. There are some other chairs in which the position of the seat pan
is fixed and the backrest moves horizontally forward and backward, so
that the effective depth of the seat pan can be adjusted.
- The
height and width of the backrest should be at least 15 inches and 12
inches respectively. It should be firm enough to provide lumbar support
that matches the curve of your lower back.
- The
backrest of your chair should widen at its base and curve in from the
sides to coincide with your body. Ensure that it does not meddle much
with your arms.
- The
backrest should allow you to recline at least 15 degrees and should be
able to lock into place for firm support.
- The
backrest should be high enough to support your upper trunk and neck/shoulder area. A headrest
should be provided if the backrest reclines more than about 30 degrees
from vertical.
- The
chair should have removable armrests and the distance between them
should be adjustable. The distance between the armrests should be at
least 16 inches.
- The
height of the armrests should be adjustable between 7 inches and 10.5
inches from the seat pan. It is better not to use fixed height
armrests, especially for chairs with multiple users.
- The
length and width of the armrests should be large enough to support your
forearm without meddling with the work surface.
20. The padding of
the armrests should be firm and soft.
- Normally,
chairs for the workstation are designed for users weighing below 275
pounds. For users weighing above 275 pounds, the chair must be designed
to support the extra weight.
Previous: Desk
Next: Telephones
Other pages on healthy
computing: Awkward
Postures
Cts
Desk
Exercises
Eyestrain
Keyboard
Lighting
Monitors
Mouse
Msd
Other
Computer Hazards Telephones
Ventilation
Work
Station Setup
Note:
While every care is taken to provide medically accurate and up to date
information in this web site, it is to be noted that this advice is not
intended to replace the advice of your physician. Before undertaking
the advice contained in this web site, you should consult a medical
professional.
Privacy
Policy
|