Computer Workstation Ergonomics

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Computer Workstation Ergonomics

• Contents
• Introduction to the Ergonomics concept.
• Contributing factors to MDSs in computer
  workers.
• Posture
• Workstation components
• Workstation environment
• Laptops

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Introduction to the Ergonomics concept.

• Ergonomics the science of work.
• The term Ergonomics is derived from the Greek
  words ergos meaning "work" and nomos meaning
  "natural laws of" or "study of.
• Ergonomics is a broad subject that can be applied
  to many aspects of our lives. Its aim is to study
  the fit between people and their environment in
  order to improve performance, well-being, safety
  and health. This environment could be at work, at
  home, during free time or public areas.
• Ergonomics occupies the no mans land between
  engineering and medicine, architecture and health
  and safety, computer science and consumer product
  design. But it is the only scientific subject
  that focuses specifically on the interaction
  between people and the things they do (Bridger,
  2003).
• Ergonomics, is defined by the Board of
  Certification for Professional Ergonomists (BCPE)
  as,
• "a body of knowledge about human abilities,
  human limitations and human characteristics that
  are relevant to design. Ergonomic design is the
  application of this body of knowledge to the
  design of tools, machines, systems, tasks, jobs,
  and environments for safe, comfortable and
  effective human use"
• (BCPE, 1993).

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Introduction to the Ergonomics concept (cont.)

• Ergonomics can be applied to all tasks and the
  environments, organisations and systems they take
  place in.
• Tasks can vary in complexity opening a jam jar,
  internet banking, using a mobile phone, surgery,
  flying a plane, office work, manual work, skilled
  work.
• Peoples activities are not carried in a vacuum
  the interaction between the user and their work
  often involves equipment or technology. This
  takes place in some form of workspace, which
  itself is located in the wider environment and
  work organisation. All of these affect task
  performance.

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Organisation
Environment
Workspace
Task
Anatomy Physiology Psychology
Technology
Equipment
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Contributing factors to MSDs in computer workers

• There are 7 groups of contributing factors
  which all exist to some degree in all workplaces.
  By only addressing only one or two factors and
  not all of them, you are unlikely to achieve the
  goal in preventing MSDs.

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Good bad back posture.

• Early studies found that lordotic postures reduce
  pressure on the nucleus pulposus as compared to
  flexed postures. It was thus assumed that
  lordotic postures reduce spinal loading.
• We now know that this is because the load is
  transferred to the posterior annulus fiborsus and
  zygapophysial joints. These latter structures are
  frequent sources of back pain, whereas the
  nucleus is not (Kulish et al. 1991).
• Thus, the concept of good posture needs to be
  re-evaluated (Adams Bogduk, 2006).
• There is no ideal sitting posture, because no
  single posture can be comfortably maintained for
  a long time, presumably because of blood flow
  restrictions in compressed or contracted tissues.
  Thus, any recommendations on good sitting
  posture must incorporate the need for
  intermittent postural adjustments.
• Realistically, it would be better to advocate a
  straight (moderately flexed) back, with the head
  and vertebral column finely balanced, so as to
  allow the supporting muscles to relax.

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Posture (cont.)

• A good position can be bad if held too long. A
  bad position can be good for variation purposes
  (but only usually for a short time).

• Upright sitting posture

• Reclined sitting

• Declined sitting

• Standing

Micro-breaks (lt 2minutes), where you can briefly
stretch, stand up or move around. 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. During this
break stand up, move around and do something else
e.g. get a drink. This allows you to rest and
exercise different muscles. 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.
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Workstation components

• Monitors
• Potential Hazards
• Viewing distance
• Too far can cause you to lean forward and
  strain to see small text. This can fatigue eyes
  and place stress on the torso because the
  backrest is no longer providing support.
• Too near can cause eyes to work harder to focus
  (convergence problems) and may require you to sit
  in awkward postures. For instance, you may tilt
  your head backward or push your chair away from
  the screen, causing you to type with outstretched
  arms.
• Viewing angle height and side-to-side
• Working with your head and neck turned to the
  side for a prolonged period loads neck muscles
  unevenly and increases fatigue and pain.
• A display screen that is too high or low will
  cause you to work with your head, neck, shoulders
  and back in awkward postures.

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A. Monitors Potential Hazards (cont.)

• Viewing time
• Viewing the monitor for long periods of time can
  cause eye fatigue and dryness. Users often blink
  less while viewing the monitor.
• Viewing clarity
• Monitors that are tilted significantly either
  toward or away from the worker may distort
  objects on the screen, making them difficult to
  read. Also, when monitors are tilted back,
  overhead lights may create glare on the screen.
  This can result in eyestrain and sitting in
  awkward postures to avoid eye glare.
• Electromagnetic fields caused by other electrical
  equipment located near computer workstations can
  result in display quality distortions.
• Dust accumulation, accelerated by magnetic fields
  associated with computer monitors and can reduce
  contrast and degrade viewing conditions.

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A. Monitors (cont.)

• Possible Solutions
• The preferred viewing distance is between 50 and
  100 cm from the eyes to the front surface of the
  computer screen. (Text size may need to be
  increased for smaller monitors).
• Top of monitor should be at or slightly below eye
  level. Centre of screen should be 15 to 20
  degrees below horizontal eye level.
• There should be adequate desk space between the
  user and the monitor (table depth). If not,
  consider the following
• Make more room for the back of the monitor by
  pulling the desk away from the wall.
• Get a flat-panel screen.
• Move back and install an adjustable keyboard
  tray.

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A. Monitors Possible Solutions (cont.)

• Position your computer monitor directly in front
  of you. Monitors should not be farther than 35
  degrees to the left or right.
• If you work primarily from printed material,
  place the monitor slightly to the side and keep
  the printed material directly in front. Keep
  printed materials and monitors as close as
  possible to each other.
• Tilt the monitor so it is perpendicular to your
  line of sight, usually by tilting the screen no
  more than 10 to 20 degrees. (You might need to
  raise your chair to elevate your line of sight).

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A. Monitors Possible Solutions (cont.)

• For bifocal users, lower the monitor (below
  normal recommendations) or raise the chair
  height, so you can maintain normal neck postures,
  whilst looking through the bottom portion of the
  lenses. But if possible, use a pair of
  single-vision lenses.
• Rest your eyes periodically by focusing on
  objects that are farther away.
• Stop, look away and blink at regular intervals to
  moisten the eyes.
• Computer workstations should be isolated from
  other equipment that may have electrostatic
  potential in excess of /- 500 volts.
• Computer monitors should be periodically cleaned
  and dusted.

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B. Keyboards

• Potential Hazards
• Keyboard placement Height
• Keyboards that are too high or too low can lead
  to awkward wrist, arm and shoulder postures. E.g.
  when keyboards are too low you may type with your
  wrists bent up, and when keyboards are too high,
  you may need to raise your shoulders to elevate
  your arms.
• Keyboard placement Distance
• Keyboard that is too close or too far away may
  cause you to assume awkward postures such as
  reaching with the arms, leaning forward with the
  torso and extreme elbow angles.

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B. Keyboards Potential Hazards (cont.)

• Keyboard design and use
• A traditional keyboard may cause you to bend your
  wrists sideways to reach all the keys.
• Keyboard tilt may cause the wrist to bend upward.
• Smaller keyboards, such as those found on
  laptops, also contribute to stressful postures.
• These postures cause pressure on tendons and
  tendon sheets during repetitive keying.
• Left hand key usage
• Most keyboards are manufactured with a 10 key
  keypad affixed to the right side of the keyboard.
  This arrangement can be limiting to left handed
  workers or right handed workers who are
  recovering from injury and are attempting to
  remain functional during their recovery.

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B. Keyboards (cont.)

• Possible Solutions
• Place the keyboard directly in front of you at a
  distance that allows your elbows to stay close to
  your body with your forearms approximately
  parallel with the floor. (10cm from the edge of
  the desk should be adequate).
• Elbows should be about the same height as the
  keyboard and hang comfortable to the side of the
  body. Shoulders should be relaxed, and wrists
  should not bend up or down or to either side
  during keyboard use.
• Remove central pencil drawers from traditional
  desks if you cant raise your chair high enough
  to achieve an adequate posture. The work surface
  should generally be no more than 2 inches thick.
• A keyboard tray may be needed if the work surface
  or chair cannot be properly adjusted, you have
  limited desk space or if your chair has armrests
  that interfere with adequate positioning.

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B. Keyboards Possible Solutions (cont.)

• The tilt of the keyboard may need to be raised or
  lowered using the keyboard feet to maintain
  straight, neutral wrist postures.
• E.g. if you sit lower in relation to the
  keyboard, by slightly elevating the back of the
  keyboard may help maintain a neutral wrist, and
  vice versa.
• Consider alternative keyboards to promote neutral
  wrist postures. These are difficult to use if you
  cannot touch type, but can be provided on a
  case-by-case basis.
• N.B. These do maintain neutral wrist postures,
  but available research does not provide
  conclusive evidence that using these keyboards
  prevents discomfort and injury.
• 7. If you are left handed, consider alternative
  left hand keyboards, or keyboards with a detached
  10 key keypad.

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C. Mouse

• Potential Hazards
• Mouse Placement
• If the mouse is not near the keyboard you may be
  exposed to awkward postures of the shoulders,
  wrist and trunk, contact stress, or forceful hand
  exertions while using the device.
• Mouse Size Shape
• Inappropriate size and shape of mouse can also
  cause awkward postures. For example, using a
  mouse that is too big or too small may cause you
  to increase finger force and deviate your wrist.
• Using the left hand to operate a mouse that is
  designed for right-hand use can also create force
  and postures issues.

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C. Mouse (cont.).

• Possible Solutions
• Position the mouse to allow you to maintain a
  straight, neutral wrist posture.
• Install keyboard trays that are large enough to
  hold both the keyboard and mouse. If not
  possible, install a mouse tray.
• Substitute keystrokes for mousing tasks, such as
  CtrlS to save, and CtrlP to print.
• Select a mouse designed to fit the hand that will
  normally operate it.
• Many devices come in sizes to fit large and small
  hands.
• A device that is designed for either hand use may
  be desirable, since changing from right- to
  left-hand operation provides periods of rest for
  one hand.

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D. Wrist/Palm Supports

• Wrists supports help to
• Facilitate neutral wrist angles.
• Reduce contact stress and irritation to soft
  tissues in wrist/palm.
• This can be especially useful in jobs that
  involve prolonged keying and mousing tasks.
• Match the wrist support to the width, height and
  slope of the front edge of the keyboard.
  (Remember, the goal is to keep wrist postures as
  straight as possible).
• Wrist supports should be around 4cm deep.
• Do not rest your wrist on the wrist supports
  while typing, since your hands should be elevated
  and move freely.
• When resting, the wrist support should contact
  the heel or palm of your hand, not your wrist!

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E. Document holders

• If documents are placed too far from the monitor,
  frequent head movements are required to look from
  the monitor to the document.
• Document holders keep printed materials needed
  during computer tasks close to the user and
  monitor.
• These should be placed at about the same height
  and distance as the monitor screen.
• If written entries are necessary, the document
  holder can be placed directly beneath the
  monitor.
• Task lighting on the document should not cause
  glare on the monitor.

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F. Desks

• Desk or work surface areas
• Limited space on the work surface may cause users
  to place components and devices in undesirable
  positions. This can lead to awkward postures as
  you reach for the mouse or look at a monitor
  placed to the side.
• Some desks and computer equipment have hard edges
  that come in contact with a users arm or wrist.
  This creates contact stress, affecting soft
  tissues including nerves and blood vessels.

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F. Desks (cont.).

• Possible Solutions
• The location of frequently-used devices
  (keyboard, phone, mouse) should remain within the
  repetitive access (primary work zone).

• Pad desk edges with e.g. pipe insulation.
• Buy furniture with rounded desktop edges.

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F. Desks (cont.)

• Areas under the desk
• Clearance for legs under the desktop, should
  generally be between
• 50 72 cm high.
• Inadequate clearance under the work surface may
  result in discomfort due to
• Users sitting too far from computer, causing them
  to reach forward to perform tasks.
• Generalised fatigue circulation restrictions
  due to constriction of movement and inability to
  frequently change postures.
• Desks that are too high or too low may lead to
  awkward postures, such as extended arms to reach
  the keyboard, and raised shoulders.

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F. Desks (cont.)

• Possible Solutions
• Provide adequate clearance space for users to
  frequently change working postures. This space
  should remain free of items such as files, CPUs,
  books and storage.

• Raise work surfaces by inserting e.g. blocks
  under the desk legs if necessary.
• Lower work surfaces by cutting desk legs, or
  raise the chair. If needed, provide a footrest.
• Remove centre drawers from conventional desks to
  create additional thigh clearance if necessary.
• Provide height-adjustable desks.

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G. Chairs

• An adjustable chair ensures
• A better fit for the user.
• Adequate support in a variety of sitting
  postures.
• Allows variability of sitting positions
  throughout the workday.
• This is particularly important if the chair has
  multiple users.

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Chair components

• Backrest
• Poor back support and inappropriate postures may
  result from inadequate backrest size, positioning
  or use.
• 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
• Be height adjustable. The backrest should be
  adjusted so that the lumbar support fills the
  curve in your back.
• Have an adjustment that allows the user to
  recline at least 15 degrees from the vertical.
• Have 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.

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Chair components (cont).

• Seat
• 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
  difficult to maintain a good posture.
• An inappropriately sized seat pan can be
• Too short causes excess pressure on the buttocks
  of taller users
• Too long places excess pressure on the knee area
  of shorter users and minimise back support.
• Too small restricts movement and provides
  inadequate support.
• Prolonged use of an inappropriately sized seat
  pan can restrict blood flow to the legs and
  create irritation and pain.

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Chair components Seat (cont.)

• Seat pan should be
• Height adjustable (especially when shared by a
  number of users). Chair height is appropriate
  when the entire sole of the foot can rest on the
  floor with the back of the knees slightly higher
  than the seat of the chair. If the seat cannot be
  lowered (e.g. making keyboard or monitor too
  high), use a footrest.
• Padded and have a rounded, waterfall edge.
• Wide enough to accommodate the majority of hip
  sizes. Chairs with oversize seat pans should be
  provided for larger users.
• Depth adjustable. Seat pan should provide
  support for most of the thigh without contact
  between the back of the users knee and the front
  edge of the seat pan. If not possible, provide a
  footrest, which elevates the knees slightly to
  relieve pressure from the back of the leg.

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Chair components (cont.)

• Armrests (optional)
• Potential Hazards
• Too low, cause you to lean over to the side to
  rest one forearm, causing an uneven posture.
• Too high, cause you to maintain raised shoulders.
• Too wide, cause you to reach with your elbow and
  bend forward for support.
• 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.

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Chair components Armrests (cont.)

• Possible Solutions
• If your armrests cannot be properly adjusted, or
  if they interfere with your workstation, remove
  them, or stop using them.
• Position armrests so they support your lower arm
  and allow your upper arm to remain close to the
  torso.
• Shoulders should be relaxed during use.
• Armrests should not interfere with chair
  positioning.
• Armrests should be made of soft material and have
  rounded edges.

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Chair (cont.)

• 4. Base
• Chairs should have a strong, five-legged base.
  Chairs with 4 or fewer legs provide inadequate
  support and are prone to tipping.
• A chair without caster makes positioning the
  chair in relation to the desk difficult. This
  increases reaching and bending to access computer
  components.

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8. Telephones

• Many office tasks today are centred around
  telephone and computers as key workstation
  components. E.g. call centres, making
  reservations etc.
• Placing the telephone too far away can cause you
  to repeatedly reach.
• Place the telephone in the primary or secondary
  work zone, depending on usage patterns.
• Prolonged conversations with the phone pinched
  between your shoulder and head may cause neck
  pain.
• Use a hands-free head set, or speaker phone
  options (the latter may annoy your co-workers).

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Workstation Environment.

• Lighting
• Bright lights shining on the display screen wash
  out images, making it difficult to clearly see
  your work.
• Bright light sources behind the display screen
  can create contrast problems, making it difficult
  to clearly see your work.
• High contrast between light and dark areas of the
  computer screen, horizontal work surface, and
  surrounding areas can cause eye fatigue and
  headaches.
• 2. Glare
• Direct light sources (e.g. windows, overhead
  lights) can cause reflected light to show up on
  the monitor.
• Reflected light from polished surfaces, such as
  desks, may cause annoyance, discomfort, or loss
  in visibility.

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Workstation environment (cont).

• Possible solutions
• For computer work, use well-distributed diffuse
  light. Provide light diffusers so that desk tasks
  (writing, reading papers) can be performed while
  limiting direct brightness on the computer
  screen.
• Place rows of light parallel to your line of
  sight.
• Reorient the workstation so bright lights from
  open windows are at right angles with the
  computer screen.
• Use blinds or drapes on windows to eliminate
  bright light.
• N.B. Vertical blinds work best for East/West
  facing windows and horizontal blinds for
  North/South facing windows.

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Workstation environment Possible Solutions
(cont.)

• Provide supplemental task/desk lighting to
  adequately illuminate writing and reading tasks
  while limiting brightness around monitors.
• Use light, matte colours and finishes on walls
  and ceilings to better reflect indirect lighting
  and reduce dark shadows and contrast.
• Use glare filters that attach directly to the
  surface of the monitor to reduce glare.
• Tilt down the monitor slightly to prevent it from
  reflecting overhead light.
• Generally, a large number of low powered lamps
  rather than a small number of high powered lamps
  will result in less glare.

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Laptop Computers

• Laptops are un-ergonomic!
• The design of laptops violates a basic ergonomic
  requirement for a computer, namely that the
  keyboard and screen are separated.
• Using a laptop is a trade-off between poor
  neck/head posture and poor hand/wrist posture.
• Potential hazards
• Neck or eye problems from trying to see the
  screen at an awkward angle.
• Wrist and hand problems from bending your wrists
  to use the keyboard (usually smaller than
  conventional keyboards).
• Shoulder or back problems from carrying the
  laptop, or from reaching too far to use it, or
  from using it extensively in an unusual posture
  such as slouching, bending over or lying down.

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• Working on a laptop Occasional users
• Because the neck/head position is determined
  by the actions of large muscles, you are better
  off sacrificing neck posture rather than wrist
  posture. Thus
• Position your laptop in the most neutral wrist
  posture that you can achieve.
• Angle the laptop screen so that you can see this
  with the least amount of neck deviation.
• Do not support the laptop on your lap (because of
  the heat).

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• Working on a laptop Full-time users
• Where possible dont use a laptop for long
  periods use a desktop instead.
• Position laptop on your work-surface in front of
  you so that you can see the screen without
  bending your neck. This may require you to
  elevate the laptop off the desk surface using a
  stable support surface, such as a computer
  monitor pedestal.
• Use a separate keyboard and mouse.
• Take more regular micro- and rest- breaks.

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Laptop weight

• If your are a mobile professional who will be
  frequently transporting your laptop think about
  the weight of the system (power supply, spare
  battery, external disk drive etc).
• If your laptop components weighs 4.5 kilos or
  more, you should consider using a carry-on bag
  that you can pull along.
• If you want a smaller bag, consider a good
  shoulder bag design.

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Thank You!
Go to http//www.magnitude.com to download a
free trial ergonomic software that will monitor
how long you have been using the computer and
prompt you to take a rest break at appropriate
intervals. Remember, working at a computer can
be hypnotic, and often you dont realize how long
youve been working!