Workstation Ergonomics

Occupational overuse syndrome (OOS) related to the use of computers is a common problem in the University so the following information is provided to assist staff and students arrange computer workstations in such a way so that the risk of such injuries is reduced.

All recommendations are based upon Australian Standard AS 3590 - 1990 Screen based workstations, part 2 workstation furniture.

Computer Workstation Dimensions
Height of work surface above floor level	Viewing distance to work
If fixed: 680mm to 720mm If adjustable: 580mm to 730mm	350mm to minimum 750mm to maximum
Area of work surface	Height of display
Width: 1500mm minimum Depth: 900mm minimum	30mm to 40mm below eye level
Volume of leg space	Seat pan height
Width: 800mm minimum Depth: 550mm minimum Height: 580mm minimum	Surface of seat to floor: 380mm to 510mm Seat pan depth: 330mm to 430mm Footrest area: 300mm x 375mm
Bench thickness over leg span
25mm maximum

Chairs and Posture Checklist for Keyboard Workers

Well adjusted chairs improve body position and circulation, reduce muscular effort and decrease pressure on the worker's back. Chairs should swivel, have five wheels for stability, breathable fabric on the seat, a rounded front edge and have adjustable height and backrest for lumbar support.

Work surface height

Adjust the height of the work surface and/or the chair so that the work surface is approximately at finger length below the height of the elbow when seated.

Chair

Adjust the seat tilt so that you are comfortable when you are using the keyboard. Usually this will be close to horizontal but tilted slightly forwards. If this places an uncomfortable strain on the leg muscles or if the feet do not reach the floor then a footrest should be used. Adjust the backrest so that it supports the lower back when you are sitting upright.

Keyboard placement

Place the keyboard in a position that allows the forearms to be close to the horizontal and the wrists to be straight. That is, with the hand in line with the forearm. If this causes the elbows to be held far out from the side of the body then re-check the work surface height.

Screen placement

Set the eye to screen distance at the distance that permits you to most easily focus on the screen. Usually this will be within an arm's length. Set the height of the monitor so tha tthe top of the screen is below eye level and the bottom of the screen can be read without a marked inclination of the head. Usually this means that the centre of the screen will need to be near shoulder height.

Desk-top layout

Place all controls and task materials within a comfortable reach of both hands so that there is no unnecessary twisting of any part of the body.

Document holder

Place this close to the monitor screen in the position that causes the least twisting or inclination of the head.

Posture and environment

• Change posture at frequent intervals to minimise fatigue.
• Avoid awkward postures at the extremes of the joint range, especially the wrists.
• take frequent short rest breaks rather than infrequent longer ones.
• Avoid sharp increases in work rate.
• Changes should be gradual enough to ensure that the workload does not result in excessive fatigue.
• After prolonged absences from work the overall duration of periods of keyboard work should be increased gradually if conditions permit.

Lighting for VDUs

Place VDUs to the side of the light source/s, not directly underneath. try to site desks between rows of lights. If the lighting is fluorescent strip lighting, the sides of the desks should be parallel with the lights. Try not to put the screen near a window. If it is unavoidable ensure that neither the screen nor the operator faces the window.

If the VDU is well away from windows, there are no other sources of bright light and prolonged desk-work is the norm, use a low level of service light of 300 lux. If there are strongly contrasting light levels, then a moderate level of lighting of 400 - 500 lux may be desirable but high quality anti-glare screens may be necessary.

Glare and reflection

It is important to detect the presence of glare and reflection. To determine whether there is glare from overhead lights the seated worker should hold an object such as a book above the eyes at eyebrow level and establish whether the screen image becomes clearer in the absence of overhead glare. To detect whether there are reflections from the desk surface the worker should hold the book above the surface and assess the change in reflected glare from the screen.

A number of ways are available to eliminate or reduce the influence of these reflections:

• Tilt the screen so that the reflections are directed below eye level.
• Purchase a screen with matt or light diffusing surfaces.
• Cover screen with a light diffusing surface or anti-glare screen.
• Negative contrast screen (dark characters on light background) will reduce the influence of these reflections.

If you experience eye discomfort when using a bright screen you should make the following adjustments:

• Turn the screen brightness down to a comfortable level.
• Look away into the distance in order to rest the eyes for a short while every ten minutes or so.
• Change the text and background colours. Recommended are black characters on white or yellow background, or yellow on black, white on black, white on blue and green on white. Avoid red and green and yellow on white.

Using a mouse

A well designed mouse should not cause undue pressure on the wrist and forearm muscles. A large bulky mouse may keep the wrist continuously bent at an uncomfortable angle. Pressure can be reduced by releasing the mouse at frequent intervals, by selecting a slim-line, low-profile mouse and by using the mouse at a comfortable distance from the body.

Keyboard equipment and radiation

VDUs emit radiation, particularly visible light which allows the characters on the screen to be seen. Weak electromagnetic fields and very low levels of other radiation, not visible to the human eye, can be detected by sensitive instruments. Similar emissions are produced by television receivers.

The levels of most radiations and electromagnetic fields emitted from VDUs are much less than those from natural sources, such as the sun or even the human body and are well below levels considered to be harmful by responsible expert bodies such as the International Radiation Protection Association (IRPA).

Given that the levels of radiation from VDUs are much lower than the recommended limits, and that these limits themselves incorporate significant safety factors, it is extremely unlikely that any harm to an unborn child would result from exposure to such radiation emissions.

The weak electromagnetic fields produced by television receivers and VDUs extend in all directions, but their intensity decreases very quickly with distance from the source. A workplace should be organised to ensure that VDU operators are no closer to any other VDUs than they are to their own.

Flat screen displays, such as liquid-crystal dispays used in some laptop/notebook computers, produce even smaller amounts of radiaiton than those which use television type tubes.

Although concerns have been raised that radiation from VDUs is a cause of cancer, research to date has failed to establish a causal link.

Keyboard and telephone operations

Lightweight adjustable headsets with a volume control should be provided for staff on continuous keyboard/telephone operation. For continuous, traffic dependent telephone operations a manual call facility should also be provided.

Use of laptop/notebook computers

Where possible and practical it is advisable that all of the principles outlined above be applied when working with these types of computers. In particular you should try and avoid awkward body postures and ensure that frequent short breaks are taken to minimise the onset of fatigue.

• Ergonomics Policy of the University of Western Australia.
• Set up for Life - guidelines for correctly setting up your computer workstation.

An animated tutorial

IBM have recently established a website called Healthy Computing, which contains lots of information and illustrations (including animation) on workplace setups and ergonomics.

Introduction to Office Ergonomics

Training to assist supervisors to correctly set up a workstation for new staff or assist existing staff experiencing musculoskeletal problems is available. Contact the OH&S Unit for details of the next scheduled session or view a PowerPoint overview of this module.