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INDUSTRIAL ERGONOMICS Office-Workstation (Computer workstation). DR. SITI ZAWIAH MD. DAWAL DEPT. OF ENGINEERING DESIGN AND MANUFACTURE UNIVERSITY OF MALAYA. Introduction. It is common now and accepted that one should sit in the office.
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INDUSTRIAL ERGONOMICS Office-Workstation (Computer workstation) DR. SITI ZAWIAH MD. DAWAL DEPT. OF ENGINEERING DESIGN AND MANUFACTURE UNIVERSITY OF MALAYA
Introduction • It is common now and accepted that one should sit in the office. • Yet, low back pain and musculoskeletal discomfort and together with eye-strain constitute the majority of subjective complaints and objective symptoms of computer operators.
Theories of Healthy Standing • The normal or healthy standing was recommended by Staffel in 19th century. • It has been used by physicians, mothers, teachers, orthopedists etc. • Even today that ”upright” or “ straight” standing posture with slight lordoses (forward bends) are considered as “good” and “proper” , “healthy”, “balanced” and “neutral “
Theories of Healthy Sitting • At least a century it was common belief that standing and sitting with a straight back is physically desirable and social proper for pupils and adults alike. • Apparently, human body is adapted to change – to moving about. • Sitting or standing still for extended periods is uncomfortable and leads to compression of tissues, reduction in metabolism and deficiency in blood circulation in the lower legs.
Good Working Positions • To understand the best way to set up a computer workstation, it is helpful to understand the concept of neutral body positioning. • This is a comfortable working posture in which your joints are naturally aligned. Working with the body in a neutral position reduces stress and strain on the muscles, tendons, and skeletal system and reduces your risk of developing a musculoskeletal disorder (MSD). • The following are important considerations when attempting to maintain neutral body postures while working at the computer workstation.
Hands, wrists, and forearms are straight, in-line and roughly parallel to the floor. • Head is level, or bent slightly forward, forward facing, and balanced. Generally it is in-line with the torso. • Shoulders are relaxed and upper arms hang normally at the side of the body. • Elbows stay in close to the body and are bent between 90 and 120 degrees.
Feet are fully supported by floor or footrest. • Back is fully supported with appropriate lumbar support when sitting vertical or leaning back slightly. • Thighs and hips are supported by a well-padded seat and generally parallel to the floor. • Knees are about the same height as the hips with the feet slightly forward.
Regard less of how good your working posture is, working in the same posture or sitting still for prolonged periods is not healthy.
You should change your working position frequently throughout the day in the following ways: • Make small adjustments to your chair or backrest. • Stretch your fingers, hands, arms, and torso. • Stand up and walk around for a few minutes periodically.
These four reference postures are examples of body posture changes that all provide neutral positioning for the body.
Upright sitting posture. The user's torso and neck are approximately vertical and in-line, the thighs are approximately horizontal, and the lower legs are vertical.
Declined sitting posture. The user's thighs are inclined with the buttocks higher than the knee and the angle between the thighs and the torso is greater than 90 degrees. The torso is vertical or slightly reclined and the legs are vertical.
Reclined sitting posture. The user's torso and neck are straight and recline between 105 and 120 degrees from the thighs.
Standing posture. The user's legs, torso, neck, and head are approximately in-line and vertical. The user may also elevate one foot on a rest while in this posture.
Semi-sitting • The major advantage of semi sitting is that the trunk is mobile particularly if there is no backrest. • It is suitable to relieve the worker from continuous standing
Adjusted Workstation Important Criteria: • Arm • Backrest • Posture • Desk • Telephone • Document Holder • Screen • Keyboard • Avoiding Eye Strain
DESIGN OF VDT WORKSTATION Visual workspace We alter our direction of gaze by moving our eyeballs within their sockets and by moving our head. It is good to have some movement of the head during work in order not to tire the neck muscles.
The head is supported by the effort of the muscles in the neck. If you hold your head still, you muscles are doing static work, that is, they are working continuously with no breaks to rest. This is more tiring than if you move your head, when the muscles are doing dynamic work, and muscles groups get a chance to rest as others take over.
Therefore, the visual aspects of the workplace should be arranged to cause the lowest level of static work by the neck muscles.
You should aim to position frequently viewed items within a comfortable zone in front of you. This is normally within 15° above, or 30° below, the horizontal, and 15° to the left and right. In the normal, relaxed position of the head, neck and eyes, the line of sight is about 10 to 15° below the horizontal, therefore, viewing horizontally straight ahead actually requires a small amount of effort.
Distance is also a factor in visual fatigue. Visual displays are comfortably viewed from 500-750mm or more, depending on the size of the display components. The lens of the eye stiffens as people get older, altering the distance at which they can easily focus, so objects need to be positioned further away for clear viewing. They also take longer to focus on things (it will happen to you one day!).
Exercise Choose the best office (computer workstation) lighting arrangements. Can you detect visibility problems that can be generated by imperfect lamp positions.
State potential hazards and give possible solutions for each figure. Figure 1
