No matter what industry you work in, computers are
commonly used. Extended work with computers can lead to
muscular fatigue and discomfort, usually in the back, arms,
shoulders and neck. The risk of a musculoskeletal disorder
(MSD) is higher for computer operators than for other office
workers. And the risk increases as the intensity of computer
work increases.
This document outlines how workstation layout, lighting,
and task design can affect the physical and visual demands on
people who work with computers. It also provides a checklist to guide your company in what to look for
when assessing computer workstations. Using a laptop and other mobile devices as the main computer in
an office poses some special challenges. Contact an ergonomist for additional tips and precautions.
Workstation Layout
Keyboard Position
When working at a keyboard, the user should sit in an
upright position with the upper arms hanging naturally from
the shoulders. The elbows should be bent at about a 90°
angle when the fingers are on the home row of the keyboard.
If the keyboard is too high, the user must raise his or her
arms and shoulders. This can cause fatigue and discomfort
and may increase the risk of injury. If the keyboard is too
low, the user has to stoop forward which can stress the arms
and the back.
In both cases, the wrists will also be strained. It is important that the equipment is positioned so that the
wrists are straight and not bent. Typically, if the keyboard is at the appropriate height, the keyboard legs
(if any) should not be raised.
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The Mouse
Hand-held input devices, such as a computer mouse, are
commonly used in computer work. A mouse should be
placed as close to the user’s side as possible and at a height
that allows the arm to hang relaxed from the shoulder. The
wrist should be in a ‘neutral’ position (that is, so the hand
is in line with the forearm). This position causes the least
physical stress. The mouse should be able to move freely.
The size and shape of the mouse are also important. For
example, to prevent cramped hand postures, different-sized
devices may be required for different users. The mouse
should also be shaped to minimize bent wrist postures.
Buttons on the mouse should be located to avoid awkward finger and hand postures. Settings can be
adjusted for left-handed users and to change the speed and distance of mouse travel and clicking actions
required. Users should loosely hold the mouse and move it from the shoulder rather than just the wrist.
This distributes muscular demands better and reduces wrist movements and static loading. Alternative
input devices are also available such as trackballs, joysticks and digitizing tablets, and may be preferred
by some users depending on task, application and/or personal preference.
Monitor Position
Proper positioning of monitors is essential to preventing
neck and eye strain. Computer monitors should be placed
so that the top of the screen is at, or slightly below, the
user’s eye level. The viewing distance between the user’s
eyes and the screen should be 50 to 100 cm.
If the screen is viewed continuously or frequently, it should
be directly in front of the worker. For bifocal or trifocal
wearers, the top of the screen should be slightly lower
(or moved back further) to avoid awkward neck posture.
An alternative is to obtain prescription lenses for computer work. Some offices have multiple monitors
which pose additional challenges. Contact WSPS for further guidance.
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The purpose of well-designed seating is to provide stable support that allows
movement, comfort and task accomplishment. Height-adjustable chairs can
help place the user at a proper height for typing, writing and viewing the
monitor, especially when height-adjustable tables are not available.
The height of the chair should allow the feet to rest flat on the floor with the
thighs roughly parallel to the floor. To place shorter workers at a comfortable
typing height, the chair may need to be raised. If a worker’s feet cannot reach
the floor, provide a footrest. The ankles are usually most comfortable at an
angle close to 90°; therefore, footrests can be inclined 0-30°.
No single sitting posture can remain comfortable if maintained for prolonged
periods of time. The workstation design, chair design and job organization
should all allow for a change in posture. Movement is important to minimize
fatigue and static effort of the muscles.
Movement may include slightly altering the angles at the neck, shoulders, elbows, wrists, hips, knees and
ankles. In chairs where computer use is the primary task, the seat height, seat angle, backrest height and
backrest angle should be adjustable independently of each other. Workers must be made aware of the
importance of adjusting their chairs correctly and know how to make the adjustments.
If the phone is frequently used, it is best not to cradle the phone on
the shoulder. To prevent such harmful postures, workers who use
a computer while on the telephone for long periods should wear
head sets.
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The best way to provide the proper screen and keyboard
heights for all users is to use split level tables or desks that
allow each height to be adjusted independently. This ensures
that almost all users, large and small, can have proper
postures as they work. Any table, desk or stand used for
computer work must be deep enough for both the keyboard
and the monitor to be in front of the worker.
The Canadian Standards Association’s Guideline on Office
Ergonomics (CAN/CSA Z412-17) recommends a minimum
of 50 cm. More space may be required for larger monitors,
or less space for flat screens. Keyboard trays and/or monitor
risers may also be used to achieve proper positioning. There
should also be sufficient leg room: 43 cm of horizontal knee
space and 60 cm of toe space.
Document Holders
Computer work often involves entering information from
source documents. These should be located beside the screen
and in the same plane. Alternatively, ‘slant board’ document
holders position the document between the monitor and the
keyboard, thus minimizing the need to rotate the neck. This
reduces the amount of head and eye movements between the
document and the screen and decreases the risk of muscular
and visual fatigue.
The best way to correctly position documents is to use an
adjustable document holder. Make sure the holder is suitable
for the size and type of documents used in your workplace.
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Lighting levels from 300 to 500 lux are generally considered to be the most appropriate. However, many
offices have twice the level of illumination with few complaints. Sometimes, it is the presence of dark
shadows contrasting with the bright computer display that causes eye fatigue. Task lighting and ambient
lighting should be balanced to reduce harsh contrast and glare.
Glare is also an important aspect of lighting: it can cause visual fatigue and discomfort and it can force
the user to adopt an awkward posture to avoid the glare.
There are different types of glare: direct, indirect and masking:
Direct glare occurs when there are bright light sources directly in the user’s field of view
(e.g., windows, etc.).
Indirect glare occurs when light from windows or overhead lighting is reflected off shiny surfaces in
the field of view, such as monitors, desks and other office equipment.
Light from sources directly overhead causes masking glare on the screen, partly obscuring what the
user is trying to focus on.
To reduce glare:
Use light absorbing curtains and blinds
Position terminals so the users line of sight is parallel to windows and overhead fluorescent lights
Position workstations between rows of overhead lights
Use parabolic filters on overhead lights (these covers only allow light to travel straight down, not
disperse at an angle)
Use indirect lighting (lighting that reflects off ceilings and walls into the work area)
As a last resort, use glass or plastic antiglare screens
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Task Design
Maintaining any posture over time is fatiguing, no matter how well the workstation is set up. As
well, continual data entry or word processing are very repetitive tasks and can further contribute to
discomfort and possible injury.
The best remedy is to take frequent breaks from computer work. For example, schedule five minutes
of work that does not use the computer for every hour worked. Computer-intensive jobs should be
re-designed to include tasks other than computer work.
Organize tasks and set up your workstation so that you can maintain a comfortable upright posture.
Items that are required for high frequency tasks, or those with a long duration, should be placed closest
to you (the primary zone in the diagram below).
Source: CSA Z412-17 Office ergonomics – An application standard for workplace ergonomics, Figure A.8
Reproduced with the permission of CSA from Z412-17 – Office ergonomics – An application standard for workplace
ergonomics, which is copyrighted by CSA. While use of this material has been authorized, CSA shall not be responsible
for the manner in which the information is presented, nor for any interpretations thereof.
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Quick Steps for Setting Up Your Computer Workstation
Step #1
Set the height of the chair so that your thighs are roughly parallel to the floor, with your feet flat on
the floor or a footrest
Your knee angle should be about 100°
The chair should have a well formed lumbar (lower back) support to help maintain the lumbar curve
Ensure the chair does not put pressure on the back of the legs
There should be enough space between the front edge of the seat pan and the back of your knee/
lower leg to fit one finger up to one fist
Step #2
Your elbows should be at an angle of 90°, with your shoulders relaxed and your arms hanging
naturally at your sides
Keep your hands in line with your forearms, so that wrists are straight, not bent up, down or
to the side
The mouse should be directly beside the keyboard
Step #3
Make sure the arm rests don’t interfere with natural movements and/or are adjustable
Step #4
Set your monitor at a height that allows you to keep your neck straight
The top of the active area of the screen shall be no higher than the users horizontal eye level when
seated in an upright posture
Step #5
Organize your work so that usual operations are within easy reach
Place documents beside the monitor on a document holder, or at an angle between the keyboard
and monitor
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Office Workstation Checklist
Use this checklist to assess your workstation for potential problems. A ‘No’ response may indicate a problem
which could lead to a musculoskeletal disorder. Make the necessary changes or adjustments for all
potential problems identified. If discomfort persists, you may require advice of an ergonomic specialist.
Office Workstation Item to Check Y N
Comments/Possible Adjustments
or Changes
1. Chair
Chair height is appropriate for the individual and work
surface height (thighs are parallel to the floor or knees
slightly lower than the hips)
Feet are fully supported on the floor or on a footrest
Chair has a stable base with five wheels or castors
suitable for the floor surface
The angle of the backrest is adjustable
The backrest height is adjustable; if not, the backrest
supports the inward curve of the lower back
If armrests are provided, they do not interfere with
natural movements
Chair seat is the appropriate size for the individual
The seat pan tilt is adjustable (+3° or -4°) for frequent
computer users
There is a space between the front of the chair and the
back of your legs (min: width of finger/max: fist)
310-AQT-01-IGDO © 2019, Workplace Safety & Prevention Services (WSPS)
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Office Workstation Item to Check Y N
Comments/Possible Adjustments
or Changes
2. Monitor, Keyboard, and Mouse
The monitor is directly in front of you, if viewed or used
When keying upper arms are hanging vertical, and
lower arms are horizontal (elbows approximately 90°)
Work is performed directly in front of you, with elbows
close to the body
The wrist is relaxed and not bent. Wrist rests are available
Mouse is placed on the same level as the keyboard
Mouse fits comfortably in your hand
The top of the active area of the screen is no higher
than the user’s horizontal eye level (lower for bifocal
wearers) when seated in an upright posture
The monitor is at a comfortable distance away
(50 to 100 cm)
Screen is free of glare or shadows
Windows are not in front or behind the operator
Letters on the screen are sharp, easy to read, and do
not flicker
310-AQT-01-IGDO © 2019, Workplace Safety & Prevention Services (WSPS)
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Office Workstation Item to Check Y N
Comments/Possible Adjustments
or Changes
3. Work Surface
Work/writing surface height is about elbow level
Work surface is large enough to hold all work material
Frequently used items are within easy reach
Reaching behind the midline of the body is avoided
Writing space is available on the individual’s dominant
side, while on the computer
Legroom is sufficient to stretch out the legs and to
swivel in the chair
4. Lighting
Adequate lighting is provided
Adjustable task lighting is available
You are shielded from glare (e.g., sun or lighting)
The workstation is located in between rows of
overhead lights
310-AQT-01-IGDO © 2019, Workplace Safety & Prevention Services (WSPS)
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Office Workstation Item to Check Y N
Comments/Possible Adjustments
or Changes
5. Accessories
A head set is provided if talking on the phone while
keyboarding is regularly required
If provided, source documents are angled upwards with
an appropriate document holder
Source documents are positioned close to your center
of attention if viewed regularly
6. Work Practices
You vary your viewing distance throughout the day by
focusing on items further away
While keyboarding your hands float over the keys, not
resting on the wrist rests
You are able to vary your tasks
You sit back in the chair properly (head and shoulders
are relaxed, not raised, hunched, or rounded), using
the backrest for support
You know how to adjust your chair, and adjust it
throughout the day
You take frequent micro breaks (5 minutes every hour)
to change posture and perform stretching exercises
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exceptional conditions or circumstances.
Revised: August 2019
Office Workstation Item to Check Y N
Comments/Possible Adjustments
or Changes
7. Laptop
If using a laptop for prolonged periods (> 2 hours) you
use an external keyboard and mouse and/or monitor to
optimize the work height and neck posture
Additional Notes: