Extended work with computers can lead to muscular fatigue and discomfort, usually in the back, arms, shoulders and neck. As well, if the computer is used for prolonged periods in awkward postures, there is a risk of musculoskeletal injury (MSI). This risk increases as the intensity of computer work increases. Frequently, the source of muscular fatigue and discomfort is the operator's posture while working at the terminal, and this posture is due in turn to the layout of the computer workstation and the furniture provided. The specific tasks and the intensity of the work are also factors. Computer operators may experience visual as well as muscular fatigue and discomfort. Symptoms include eyestrain, burning eyes, blurred vision and headaches. The layout of the computer workstation can increase the visual demands on operators, as can lighting levels and glare.
WORKSTATION LAYOUT
This section describes postures that seek to minimize postural demands. However, it should be noted that any one posture becomes fatiguing after a while, and that changes in posture are important. Thus the posture described and illustrated in Figure is a guideline as to general suitability of posture, and is not the only recommended posture. As noted in the CSA guideline movement is important to minimize postural fatigue and discomfort. Movement may include slightly adjusting the positioning of the head, shoulders, arms, back, hips, and legs. For example, hip angle changes as a person reclines in their chair. Leg and hip angles change as a person stretches their legs out in front. Shoulder and arm angles can be changed by moving the chair forward or back slightly.
KEYBOARD POSITION
When working at a keyboard, the operator should be sitting with the upper arms hanging naturally from the shoulders. The elbows should be bent at roughly a 90-degree angle when the fingers are in typing position on the home row of the keyboard. This posture allows the arms and wrists to be held in a natural and relaxed position that puts the least amount of physical stress on muscles and joints.
If work surfaces are too high, users must raise their arms and shoulders. This requires continuous muscular effort, called "static effort" or "static loading". This static effort in the arms and shoulders may be fatiguing, and it may also hinder blood flow, adding to discomfort and even to the risk of injury. In addition, the wrist may be flexed (bent forward) to reach the keys, placing stress on forearm muscles and wrist tissues. If the work surfaces are too low, the worker must lean forward, placing stresses on the arms and back. As well, the wrists will tend to be bent back, also stressing the muscles and tissues. A desk height that is too high or too low for writing can result in the same kinds of problems.
1) The monitor should be set at a height so that your neck will be straight.
2) Your elbow joints should be at about 90 degrees, with the arms hanging naturally at the
sides.
3) Keep your hands in line with the forearms, so the wrists are straight, not bending up, down or to either side.
4) Thighs should be roughly parallel to the floor, with your feet flat on the floor or footrest.
5) If necessary, use a footrest to support your feet.
6) Your chair should be fully adjustable (i.e. for seat height, backrest height and seat pan tilt,
and, preferably, armrests). It should have a well-formed lumbar (lower back) support to help
maintain the lumbar curve.
7) There should be enough space to use the mouse. Use a wrist rest or armrest so that your wrist is straight and your arm muscles are not overworked.
8) Use an adjustable document holder to hold source documents at the same height, angle and
distance as the monitor.
If work surfaces are too high, users must raise their arms and shoulders. This requires continuous muscular effort, called "static effort" or "static loading". This static effort in the arms and shoulders may be fatiguing, and it may also hinder blood flow, adding to discomfort and even to the risk of injury. In addition, the wrist may be flexed (bent forward) to reach the keys, placing stress on forearm muscles and wrist tissues. If the work surfaces are too low, the worker must lean forward, placing stresses on the arms and back. As well, the wrists will tend to be bent back, also stressing the muscles and tissues. A desk height that is too high or too low for writing can result in the same kinds of problems.
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| This diagram is just an example. Workstation set ups will vary according to the particular desk style, monitor, tray mount or other accessories used. |
2) Your elbow joints should be at about 90 degrees, with the arms hanging naturally at the
sides.
3) Keep your hands in line with the forearms, so the wrists are straight, not bending up, down or to either side.
4) Thighs should be roughly parallel to the floor, with your feet flat on the floor or footrest.
5) If necessary, use a footrest to support your feet.
6) Your chair should be fully adjustable (i.e. for seat height, backrest height and seat pan tilt,
and, preferably, armrests). It should have a well-formed lumbar (lower back) support to help
maintain the lumbar curve.
7) There should be enough space to use the mouse. Use a wrist rest or armrest so that your wrist is straight and your arm muscles are not overworked.
8) Use an adjustable document holder to hold source documents at the same height, angle and
distance as the monitor.
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