Ergonomics for computer operator

                           

The use of computer is widespread at almost all workplaces in offices and production units now a days. This growing population has been subjected to increased diversity in their work pattern, associated with human computer interaction environment. Literatures from West indicate that the repetitive nature of computer work results in an increased incident of health problems, e.g., visual and muscuclo-skeletal discomfort, psycho-physiological as well as psychosocial stresses among professional computer users. Musculo-skeletal pain and discomfort (together with eye strain) constitute at least half, in some surveys up to 80 percent, of all complaints and symptoms of computer operators. One of the enduring concerns of the human-computer environment is to mitigate the effects of changed work characteristics and stresses on the ultimate outcome variables (e.g. work performance, reliability, health and comfort.) There is the interrelationship between posture, comfort, reliability and performance in computer based tasks. .

Here we will discuss:

• Factors of work stresses of computer users including long-term effects of musculo-skeletal system.
• Interrelationships between posture and comfort.
•  Measures to mitigate the stress and strain and remedial work design interventions for computer operators.

People who do continuous, intensive computer work, such as data entry, for prolonged periods during a shift are at increased risk of developing a number of health problems. These include: visual fatigue, headaches, upper limb musculoskeletal injuries (e.g., carpal tunnel syndrome), and back pain.

While seeing to the ergonomics, three matters are to be kept in mind.

• Awkward position
• Duration
• Repetitive motions        

Awkward Positions

Body postures determine which joints and muscles are used in an activity, as well as the amount of force exerted. Poor postures place unusual or excessive forces on components of the body. Examples of poor positions include keeping a computer mouse far from the keyboard or not locating the keyboard and monitor in a straight line from your seat. These kinds of awkward positions create undue stresses at the wrists, shoulders, and neck.

Duration

This refers to the amount of time a person holds a static position to perform a given task. The longer the same muscle or muscle group is used, the greater the likelihood of both localized and general fatigue. This is why rest breaks or changing tasks is so important to decrease prolonged static postures and thereby reduce the risk of injury. Also important is the use of position aides—such as foot rests, copy holders, adjustable chairs, and keyboard trays—to minimize fatigue to muscle groups not directly involved in the computer work activity.

Repetitive Motions(continuous monotonous activity)

Motions performed only infrequently, even if performed in an awkward position, seldom result in any bodily harm. However, as a particular motion becomes more and more frequent, the risk of injury increases. With keyboard work, some motions are repeated as often as every few seconds, and some even faster. When performed for prolonged periods, e.g., hours without a break, fatigue and strains accumulate. Changing tasks during the day, or taking periodic breaks, can provide muscles and tendons with the time needed to recover to their normal, unstressed state.

It is very important for you to be aware of risk factors that can lead to potential work related musculoskeletal problems. Awareness of these risks can help you to avoid discomfort and injury when using a computer.

Risk factors	Tips to reduce risk
repetition	Alternate tasks.. Take frequent breaks.
Awkward postures	Sit supported against the back of your chair. Keep spine straight. Shoulders back and relaxed, arms at sides, elbows at 100 to 110 degrees, wrist neutral or bent forward slightly. Knees and ankles at 90 degrees, thigh and feet well supported. Keep work materials within reach. Use a headset for frequent phone use. Change positions frequently.
Force	Key with a light touch. Avoid prolonged or excessive grip of mouse
environment	Reduce glare on screen. Rest eyes in between.

	Chairs

Adjust the seat tilt so that you are comfortable when you are working on the keyboard. Usually, this will be close to horizontal but some people prefer the seat tilted slightly forwards.

Your knees should be bent at a comfortable angle and greater than 90º flexion. 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. The footrest height must allow your knees to be bent at 90º; the height of the footrest may need to be adjustable.

Adjust the backrest so that it supports the lower back when you are sitting upright.

 

 Phones

Avoid cradling the phone between your head and shoulder when answering calls. If you need to use your computer at the same time, use a headset or the phone's hands-free/speaker-phone .

Monitors

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 that the 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. Your eyes should be level with the tool bar.

People who wear bifocal or multi-focal lenses will need to get a balance between where they see out of their lenses and avoid too much neck flexing.

Document holder

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

Desks

Adjust the height of the work surface and/or the height of the chair so that the work surface allows your elbows to be bent at 90º, forearms parallel with the floor, wrist straight, shoulders relaxed.

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. Most people prefer the document holder to be between the keyboard and the monitor. There are many different types of document holders available.

Lighting

Place the monitor 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.

Glare and reflection

It is important to detect the presence of glare and reflection. To determine whether there is glare from overhead lights, sit down and 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, hold the book above the surface and assess the change in reflected glare from the screen.

You can eliminate or reduce the influence of these reflections in a number of ways:

Tilt the screen (top part forwards) so that the reflections are directed below eye level.

Cover the 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 10 minutes or so.

Change the text and background colours. We recommend 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 and by selecting a slim-line, low-profile mouse. Keep the mouse as close as possible to the keyboard, elbow bent and close to the body.

Keyboard

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.Some people prefer to have their wrists supported on a wrist rest or the desk. Be careful not to have the wrist extended or bent in an up position.

Typing is a physical activity, and using a keyboard requires skill, hence the need to learn correct typing technique. Unskilled   typists are particularly at risk of "occupational overuse injury" because they:

• often use only one or two fingers which may overload the finger tendons
• are constantly looking from keyboard to screen to keyboard, which may strain neck muscles
• often adopt a tense posture (wrists bent back and fingers 'poised to strike').

It is recommended that operators take regular postural/stretching breaks to reduce intense periods of repetitive movement.

Posture and environment

Change your posture at frequent intervals to minimize 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.