A chair that is well-designed
and appropriately adjusted is an essential element of
a safe and productive computer workstation. A good chair
provides necessary support to the back, legs, buttocks,
and arms, while reducing exposures to awkward postures,
contact stress, and forceful exertions.
- The backrest should conform
to the natural curvature of
your spine, and provide adequate
- The seat should be comfortable
and allow your feet to rest
flat on the floor or footrest.
- Armrests, if provided, should
be soft, allow your shoulders
to relax and your elbows to
stay close to your body.
- The chair should have a
five-leg base with casters
that allow easy movement along
Increased adjustability ensures a better fit for the
user, provides adequate support in a variety of sitting
postures, and allows variability of sitting positions
throughout the workday. This is particularly important
if the chair has multiple users.
To ensure that the chair will
provide adequate support, it is important that you try
out different chairs before purchasing one.
The following parts of the chair are important elements
to consider in creating a safe and productive workstation:
You should adjust your chair
along with appropriately placing your monitor,
- Poor back support and inappropriate postures
may result from inadequate backrest size, material,
positioning, or use. Working in these postures
may lead to back pain and fatigue. For example,
a chair without a suitable or adjustable backrest
will not provide adequate lumbar support or
help maintain the natural S-shape curvature
of the spine.
Adjustable chair and backrest
- If your current chair does not have a lumbar
support, use a rolled up towel or a removable
back support cushion to temporarily provide
support and maintain the natural curve of the
- Use a chair with a backrest that is easily
adjustable and able to support the back in a
variety of seated
postures. A backrest should have the following:
- A lumbar support that is height adjustable
so it can be appropriately placed to fit the
lower back. The outward curve of the backrest
should fit into the small of the back.
- 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 to provide adequate resistance
to lower back movement.
- A device enabling it to move forward and
backward. This will allow shorter users to
sit with their backs against the backrest
without the front edge of the seat pan contacting
their knees. Taller users will be able to
sit with their backs against the backrest
while still having their buttocks and thighs
fully supported. Note:
some chair designs provide this adjustability
by adjusting the position of the seat pan.
Natural S-curvature of the spine
Knee slightly higher than the seat of the
Seat pan with a rounded,
- Using a chair with a seat that is too high
may force you to work with your feet unsupported
or encourage you to move forward in the chair
to a point where your back is unsupported making
it more difficult to maintain the S-shape of
the spine (Figure 2). These awkward postures
can lead to fatigue, restricted circulation,
swelling, numbness, and pain.
- If the seat cannot be lowered (for example,
it would make the keyboard or monitor too high),
use a footrest to provide stable support for
the feet (Figure 3).
- Provide a chair with a seat pan that is adjustable
and large enough to provide support in a variety
postures. It is recommended that the seat
- Height adjustable, especially when shared
by a number of users. The chair height is
appropriate when the entire sole of the foot
can rest on the floor with the back of the
knee slightly higher than the seat of the
chair (Figure 4).
- Padded and have a rounded, "waterfall"
edge (Figure 5).
- Wide enough to accommodate the majority
of hip sizes. Chairs with oversize seat pans
should be provided for larger users.
- An inappropriately sized seat pan can be uncomfortable,
provide inadequate support to the legs, and
restrict movement. One that is too short can
place excess pressure on the buttocks of taller
users, one that is too long can place excess
pressure on the knee area of shorter users and
minimize 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.
- Seat pan should be "depth" adjustable
to adequately support taller users while allowing
shorter users to sit with their back fully supported.
The seat pan should provide support for most
of the thigh without contact between the back
of the user's knee and the front edge of the
- Provide a footrest, which may elevate the
knee slightly to relieve pressure on the back
of the leg.
- Provide a chair that is sized to fit small
or large users. Note:
this is especially important if the chair is
to be shared by several users.
Using an armrest is up to you and the system integrators.
Consider factors such as the amount of time during
the workday that the user performs computer work,
whether the user is experiencing or has experienced
a musculoskeletal disorder (MSD) or symptoms,
and user preference.
Shoulders in various positions
- Armrests that are not adjustable, or those
that have not been properly adjusted, may expose
you to awkward
postures or fail to provide adequate support. For example armrests that are:
- Too low may cause
you to lean over to the side to rest one forearm.
This can result in uneven and awkward postures,
fatiguing the neck, shoulders, and back.
- Too high may cause
you to maintain raised shoulders (Figure 6),
which can result in muscle tension and fatigue
in the neck and shoulders.
- Too wide (Figure
6) cause you to reach with the elbow and bend
forward for support. Reaching pulls the arm
from the body and can result in muscle fatigue
in the shoulders and neck.
- Too close can
restrict movement in and out of the chair.
- 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 need
to reach and lean forward in your chair. This
can fatigue and strain the lower back, arm,
- Armrests that are made of hard materials or
that have sharp corners can irritate the nerves
and blood vessels located in the forearm. This
irritation can create pain or tingling in the
fingers, hand, and arm.
Office chair with adjustable armrests
- If your armrests cannot be properly adjusted,
or if they interfere with your workstation,
remove them, or stop using them.
- Position adjustable armrests so they support
your lower arm and allow your upper arm to remain
close to the torso. Properly adjusted armrests
- Wide enough to allow easy entrance and
exit from the chair,
- Close enough to provide support for your
lower arms while keeping your upper arms
close to the body,
- Low enough so your shoulders are relaxed
during use (Figure 6) (Adjust your armrests
so they just make contact with your lower
arms when positioned comfortably at your
- High enough to provide support for your
lower arms when positioned comfortably at
your sides. You may be able to add padding
to the top of your armrests if they are
too low and not adjustable.
- Armrests should be large enough to support
most of your lower arm but small enough so they
do not interfere with chair positioning.
- Armrests should be made of a soft material
and have rounded edges.
- Chairs with four or fewer legs may provide
inadequate support and are prone to tipping.
- Inappropriate choice of casters, or a chair
without casters, can make positioning the chair
in relation to the desk difficult. This increases
reaching and bending to access computer components,
which can lead to muscle strain, and fatigue.
Chair with five-leg base
- Chairs should have a strong, five-legged base.
- Ensure that chairs have casters that are appropriate
for the type of flooring at the workstation.