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Computer & Health



Computer&Health


Contents :-



Introduction


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Ergonomics is the science of fitting jobs to workers by taking into account the requirements of the job and peoples’ physical and mental capacities. It is the science of ergonomics that is used to design an appropriate computer workstation. When workstations are not designed appropriately, when non-ergonomically designed computer equipment is used and when jobs and tasks are not well organized, a number of computer related health problems can arise.

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Eye and vision problems

Eye and vision problems have been reported; in fact, eye and vision complaints are the most common complaints of computer users. Vision problems can contribute to the physical disorders. We tend to position ourselves so that we can see the images on the monitor, keyboards and documents. However if our vision is blurry, we may lean forward and crane our necks to get a closer look. Such awkward positions increase the risk for physical disorders. It is therefore important to have regular eye check ups. In addition, computer work tends to exacerbate other vision problems. Special computer glasses exist that may help with computer work. Adequate lighting and the prevention of glare also play a role in how our vision is affected during computer use. Eye and vision problems have been reported; in fact, eye and vision complaints are the most common complaints of computer users. Vision problems can contribute to the physical disorders listed below. We tend to position ourselves so that we can see the images on the monitor, keyboards and documents. However if our vision is blurry, we may lean forward and crane our necks to get a closer look . Such awkward positions increase the risk for physical disorders. It is therefore important to have regular eye check ups. In addition, computer work tends to exacerbate other vision problems. Special computer glasses exist that may help with computer work. Adequate lighting and the prevention of glare also play a role in how our vision is affected during computer use.

Stress

Stress is also reported by computer users. The National Institute of Occupational Safety and Health found that operators of computers experience more job stress than any other occupational group it has studied.

Work related musculoskeletal disorders, also known as Cumulative Trauma Disorders or Repetitive Strain Injuries, are a group of health problems caused by over-use or misuse of muscles, tendons and nerves.


Computer workstation design


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Workstation Layout
A good computer workstation layout can reduce the risk of experiencing computer related health problems. A good workstation layout as shown in Figure 1 should allow the computer user flexibility to reach, use and read the computer monitor, keyboard, mouse, source document, document holder, phone and other office accessories.

Therefore, how we arrange the workstation to fit our individual needs is probably the most important consideration to work comfortably. There are no established guidelines on how you should position your computer, it all depends on your comfort.

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Some tips that can be followed to arrange your workspace:

• Ensure there is sufficient desk space to allow you to put your keyboard, mouse, computer monitor, document holder, telephone and other accessories within a comfortable reach. A good rule of thumb is to have everything you need within a 16" reach.
• Avoid clutter and crowding by adding shelves or file cabinets.
• Position the work materials and the office equipment used regularly in front of you so that you do not have to constantly reach out and put yourself in an awkward posture.
• If you spend a lot of time on the phone and computer at the same time, use a headset to prevent you from reaching or cradling the phone in your neck.
• If you need to move around while on the phone to get access to files, use a cordless headset or a longer cord to prevent over reaching and awkward posture.

Don’t & do’s

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Space & positioning


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Space
In a multi task office environment where a computer is a necessity, it is important that the workstation provide maximum flexibility to accommodate not just the equipment, but also the space required for the task, an L-shape desk, which is ideal for working at the computer on one side of the desk, and provides space to do non-computer tasks on the other side. In addition, this set-up places the computer screen, keyboard, mouse, phone, task light and document holder in a centralized location and within the 16" radius, which prevents reaching out when using the equipment.

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Positioning

In designing a workstation, the type of task performed at the computer may determine the workstation layout. The placement of the computer monitor, input devices and computer accessories should be matched to the task. For example, proper keyboard location depends on how often the keyboard is used, whether the keying activity is a one- or two-handed task and how often visual guidance is required to locate specific keys during the task.

Work space positioning for: Data Entry

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In a data entry job, the computer user concentrates more on looking at the source document, with only brief glances at the monitor. Frequently the data input is numerical in nature. The keyboard placement and the use of document holder are important. For data entry, it is best to place the keyboard directly in front of the keying hand and leave a large area free for the activity of the other hand. There should be sufficient work surface space to perform these tasks.

Work space positioning for Data Retrieval

In data retrieval, the computer user brings up information from the computer and reads it on the monitor, or scans for specific information, often writing it down. The user mainly looks at the monitor; therefore, the placement of the monitor is more crucial than the keyboard and document holder. Adequate space for writing is also important.

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Work space positioning for: Word Processing

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Word processing tasks require both data entry and data retrieval. The user spends about half of the time viewing the monitor and the other half at the source document. Therefore, the placement of the monitor, keyboard and the document holder are all equally important. Text entry requires equal use of both hands for keying, so the keyboard should be directly in front of the user and at a comfortable height.

Work space positioning for: Graphic Design

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In designing graphics and drawings, the user relies on the mouse and bit pen to enter the information in the computer. The user constantly looks at the monitor. Therefore, the monitor should place directly in front of the user, with easy access to the mouse.


Desk


As people come in different heights and perform different tasks, the computer desk should provide adjustability in order to minimize stressful posture and reaching. The workstation should be adjustable to accommodate individual workers for all applications.

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The dimensions of the computer desk should be such that:

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1. An ideal computer desk should have two levels with each level adjustable for height. One level is for the monitor and one for the keyboard and mouse. The level for the monitor should be at least 20" wide (24" preferred) to provide adequate work space for the monitor, document holder, and other equipment needed for all tasks performed at that workstation.

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Most people do not have a computer desk and use their computers on a regular work desk. As work desks are not adjustable it then becomes important that an adjustable chair and keyboard tray be available.

2. Adequate clearance under the desk should be provided for the computer user’s legs and feet. According to PEOSH VDT guidelines, one way to ensure the clearance requirement is to image an object shaped like a "clearance envelopes", and to provide that amount of space.

3. The height of the top surface of the keyboard tray from the floor should be adjustable to a range of 23"- 28". The keyboard tray should also allow the user to adjust the angle of the surface so that the user’s wrists and elbows can be in neutral or slightly downward position during keying

4. The computer desk should be height adjustable so that the topmost line of the computer monitor is eye level for the user. The height of the monitor surface should permit the location of center view of the screen to be between 5 to 30 degrees below the horizontal plane through the eyes. Appropriate display height can be accomplished by adjusting the display surface or installing a monitor stand that is height adjustable. If the monitor is too low, the monitor height can be raised by stacking monitor risers/books or installing a computer support arm. If the monitor is too high, take the monitor off the computer processing unit, or lower the desk, or raise the chair and obtain a foot rest.

The preferred viewing distance for the monitor ranges between 18 and 24 inches.


Chair


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Chair Height

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The chair height should:

• Allow the user to rest the entire sole of his or her foot on the floor or footrest.
• In combination with the work surface heights, allow the user to achieve a suitable keyboard to forearm relationship and adequate leg clearance. The forearm should be parallel to the floor and the wrists in the same plane as the forearm.
• Be adjustable from seated position without tools. The minimum range of adjustment should be 16-20.5 inches.

Backrest

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A proper backrest should:

• Support the entire back including the lower region and provide a comfortable posture that permits frequent variation in a sitting position.
• Have the backrest angle and height easily adjustable. The backrest should be able to tilt at least 85 degrees to 100 degrees while still able to maintain at least a 90 degree sitting angle.
• Have range height of 16-20 inches from the seat pan and at least 13 inches wide.

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• have sufficient tension to provide adequate support for the lumbar area as well as the middle and upper back.
• Have a lumbar support that protrudes 1-2 inches and runs across the backrest. The width of the lumbar support should be at least 12 inches and the height of the lumbar support (measure at the center of the lumbar support) from the seat should be adjustable to a range of 6-10 inches. A range of adjustability of more than 3 inches is desirable if the lumbar support height is adjustable.

Seat Pan

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The seat pan should:

• have enough depth to allow contact between the user’s lumbar region and the seat back. The depth of the seat should be between 15 to 18 inches and 18 inches wide.
• have a "waterfall" design at the front of the seat, i.e. slightly concave with a softly padded round edge. The purpose of the "waterfall" design is to avoid pressure on the back of the leg above and below the knee.
• allow the user to adjust its angle and should ensure the angle between the upper and lower leg is at least 60 degrees and no more than 100 degrees when the lower leg is perpendicular to the floor. The adjustment range should allow backward tilt to at least 8 degrees (10 degrees preferred) and forward tilt to a maximum 5 degrees from horizontal. Because some tasks require leaning forward, such as reading poor quality documents, leaning forward should be accomplished by tilting the seat, not the torso, as sitting at less than 90 degrees from the thighs puts pressure on internal organs.


Mouse & keyboard


The keyboard and mouse support surface (also known as keyboard tray/platform) plays an important role as it allows you to position yourself in a proper body posture which will reduce the risk of developing computer related injury.

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There are several advantages of having a adjustable keyboard tray; it:

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• Allows you to adjust it to the proper height so that you can have knee clearance.
• Allows you to adjust it so that you are not too far nor too close when looking at the monitor. The preferred viewing distance for the computer monitor ranges between 18 and 24 inches.
• Allows you to position yourself in a neutral position while keying. The preferred body posture is elbows and hands parallel to the floor and wrists straight or slightly in a downward position.
• Allows you to avoid unnecessary arm extension when keying or mousing.
• allows you to free up more work space on your desk for other tasks, and
• Allows you to easily store away the keyboard when it is not being used.

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Keyboards

Keying on a computer keyboard has been associated with causing musculoskeletal disorders because of the improper placement of the keyboard in the workstation. When a keyboard is placed on a desk or other surface which is not at the correct height, or on a keyboard tray which is not ergonomically designed, this causes the wrist to bend outward (A) and upward (B) which increase the risk of injuries while keying on the keyboard. EOHSS recommends using height adjustable keyboard trays with a mouse platform rather than investing in the alternative keyboards.

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Wrists bent outward

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Wrists bent upward

Pointing Devices

With more and more of the computer programs designed in window environment and an increasing popularity in the internet, the use of the mouse over keying has also increased. Unfortunately, there has also been an increase in mouse-related injury.

The following cause the most mouse-related injuries:

Mouse position

• People often place their mouse away from their bodies, especially when their desks have a small keyboard tray that cannot accommodate a mouse. Then the mouse is likely to be up on the desktop, causing them to reach and extend their arm which requires greater shoulder action. When this situation occurs the shoulder is required to act frequently, resulting in fatigue and potentially a repetitive strain of some shoulder muscle’s

Grip

• Many people have developed musculoskeletal disorders from holding the mouse with too great a force. By squeezing the mouse tight it can cause the hands and arms to tire easily and may lead to possible muscle strain.

Mousing postures

• As to the keyboard, many people tend to hold and move their mouse in awkward postures as shown in Figure 1. These postures impose abnormal forces on the tendinous structures of the wrist which can lead to fatigue, pain and injury.

Incorrect Mouse Postures

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Force and awkward wrist movement

• Many people use tremendous force to drag and move the mouse up and down and from side to side to move the cursor to the desired point. The unresponsiveness of the mouse is due to losing contact with the mouse pad or clogging of the ball mechanism. In addition, some people bend their wrist inward or outward when mousing which increases the risk of injury.


Monitor


Most new computers have separate, adjustable keyboards and monitors that allow the keyboard and monitor to be positioned appropriately for the user. This is important because depending on the tasks, the computer user may spend a considerable amount of time viewing the monitor.

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There are some basic features to be considered when choosing a monitor:

• The monitor should be adjustable for tilt. By tilting the monitor, bright spots or washout caused by the overhead light on the monitor screen, can be reduced. In addition, it is also recommended to tilt back the monitor so that the top is slightly farther away from the eyes than the bottom. As we look around our surroundings, objects in the upper part of our peripheral vision are generally farther away than the point we are looking at, and objects in the lower part of our peripheral vision are usually closer. As a result, our visual system has developed to perform best when the visual plane tilts away from us at the top.

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• The monitor should be able to swivel horizontally. Depending on the tasks, the user should be able to adjust the monitor for an optimum viewing angle. See Workstation layout for monitor arrangement for specific task.
• The monitor should be adjusted for brightness and contrast. The brightness and contrast adjustment panel is usually located in front of the computer monitor. The brightness of the monitor should match the brightness of the surroundings to avoid eyes strain. It is easier to read the monitor if the contrast of the monitor is adjusted correctly. Contrast is the difference in brightness between the image produced by the monitor and the image reflected off the monitor. In addition, it is also preferable to view a monitor that has white or light color than a dark color background. Working on a computer program that has black letters and white background can reduce the difference in contrast between the screen and what is reflected off it.
• All exposed surfaces of the monitor should be finished in a neutral color with a non-reflective matte finish to minimize bright color and glare from the these surfaces.



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