Theories of “Healthy” Standing
The “normal posture as recommended by Staffel and his 19th century contemporaries and has been promoted ever since by physicians, orthopedists, physical therapists, mothers, teachers, and military superior. Even today, that “upright” or “straight” standing posture with slight lordosis (forward bends) in the lumbar and cervical spines and a light kyphosis (backward bend) in the thoracic spine is stereotypically considered “good and proper” and is often called healthy, balanced, or neutral.
Theories of “Healthy” Sitting
Sitting Upright? Staffel recommended an erect posture of the trunk, neck and head, with normal slight lordoses in the lumbar and cervical areas and a light kyphosis in the thoracic spine, similar to the desired back posture when standing erect. The simple concept that sitting upright, with the thighs horizontal and the lowerlegs vertical, means “sitting healthily” endured for a surprisingly longtime.
Maintaining Lumbar Lordosis When one sits down on a hard, flat, surfaces, without a backrest, the ischial tuberosities ( inferior protuberances of the pelvic bones) act as fulca around which the pelvic girdle rotates under the weight of the upper body. Since the bones of the pelvic girdle are linked by connective tissue to the thighs and lower trunk, rotation of the pelvis affects the posture of the lower spinal column, particularly the lumbar region.

If the rotation of the pelvis is rearward, the normal lordosis of the lumbar spine is flattened.

Inclined surface Flat surface
Given the tissue connections between the pelvis an thigh-particularly the effects of muscles spanning the hip joint or even both the knee and the hip joints , the actual hip and knee angles are also affect the location of the pelvis and hence the curvature of the lumbar spine. A large hip angle, a forward rotation of the pelvis on the ischial tuberosities is likely accompanied by lumbar lordosis.
There Is No One Healthy Posture Neither theories nor practical experiences endorse the idea of a single proper, healthy, comfortable, efficient sitting posture. Thus, the traditional postulate that everybody should sit upright and that furniture should be designed to end that is mistaken. Instead, there is a general agreement that may postures may be comfortable (healthy, suitable, efficient, etc.) for short periods, depending on one’s body, preferences, and work activities. Consequently, furniture should allow body movements and various postures. For variation, furniture should permit easy adjustment in its main features, such as the seat height and angle, back-rest position, and knee pads and footrests; the computer workstation should allow easy various in the location of the input device and the display.
“Free Posturing”
According to a report, while reading, persons often assumed a kyphotic lumbar curve even when sitting on a chair with lumbar pad that should have produced a lordosis. Apparently people sit the way they wanted.
The “free-posturing” design principle has these basic ideas: * Allow the operator to freely assume a variety of sitting (or standing) postures, adjust the workstation to her or his preferences, and even get up and move about. * Design for a variety of user preferences. * Use new technologies as soon as possible at the workstation.
Shape of the backrest A desired lumbar lordisis could be achieved simply by opening the hip angle to more than 90 degrees. Sitting on a tall, forward-declined seat pan with declining thighs rotates the pelvis forward and bends the lumbar spine into lordosis. This kind of sitting and seat has been advocated repeatedly , but has not received widespread acceptance, regardless of whether a backrest attached to the seat. A well-designed backrest alone could bring about lordosis of the lumbar spine by pushing that section of the back forward. There are more subtle and agreeable ways, however, to promote lumbar concavity-for example, by a fixed lumbar pad, a portable pad, inflatable lumbar cushions incorporated into the seat back of car and airplane seats and adjustable lumbar supports in some office chairs.
Shape of the whole chair
One can shape the total backrest to support the back fittingly: these shapes follow the curvature of the rear side of the human body: concave at the bottom, to accept the buttocks; convex slightly above, to fill in the lumbar lordosis; then rising nearly straight, but declined backward to support the thoracic area; and then convex again at the top, to follow the neck lordosis.

Comfort vs. Discomfort The concept of comport, as related to sitting, was exclusive as long as it was defined, simply and conveniently, but falsely, as the absence of discomfort. Discomfort is expressed in such terms as feeling stiff, strained, cramped, tingly, numb, unsupported, fatigued, restless, sore, and in pain. Comfort in sitting condition in terms of well-being if we feel supported, safe, pleased and content; in terms of biomechanics if we are relaxed and restful; and in terms of felt sensation if we are under the impression of experiencing warmth, softness, plusness, and spaciousness. Helander and Zhang characterized discomfort and comfort separately with respect to sitting in a chair by means of seven respective statement ;
DISCOMFORT
1. I have sore muscles. 2. I have heavy legs. 3. I feel uneven pressure. 4. I fell stiff. 5. I feel restless. 6. I feel tired. 7. I feel uncomfortable.
COMPORT
1. I feel relaxed. 2. I feel refreshed. 3. The chair feels soft. 4. The chair is spacious. 5. The chair looks nice. 6. I like the chair. 7. I feel comfortable.
Person
Workstation Design
Furniture
Equipment
Environment
Work postures
Work activities
Task
Person’s well-being
Ergonomic Design of The Office Workstation

Output
Performance

The work tasks, the work postures, and the work activities all interact and are influenced by the workstation conditions, including furniture and other equipment, and by the environment. Work postures and activities determine, to a large extent, the person’s physical well-being and work output.
For the layout of the workstation and the task, it is useful to think of three main links between a person and the job: 1. Visual interface: One must look at, among other things, the keyboard, the computer screen, the printed output, and source documents. 2. Manipulation: The hands keys, a mouse or other input devices, manipulate a pen and paper, and hold telephone. 3. Body support: The body is linked to the seat at the undersides of the thighs and buttocks and at the back with the backrest. Armrests or wrist rests may be other support links.
Designing the Visual Interface
Document Holder Document holders are designed to hold reference materials so that they can be positioned according to the visual needs of the user.
Position
A-frame (or writing slopes) should be positioned between the keyboard and the screen to support papers. Upright movable document holders should be positioned next to the screen at the same height and visual distance from the user as the screen.
COMPUTER

Placing the visual target
The problem of placing all the displays is mostly one of available space within the center of the person’s field of view. The natural way of focusing at a near target with the least effort is to incline the head slightly forward and rotate the eye balls downward (not holding the trunk and neck erect and looking straight ahead at the screen). Suggested angles of the line of sight to observe keyboard and display with current computer workplace technology.

Proper Office Lighting
For the engineer, the most important design factors are illumination, luminance, luminous contrast, and how they are distributed. * Illumination is the amount of lightning falling on a surface. The light may come from the sun or from luminaires. * Luminance is the amount of light reflected or emitted from a surface. Light may be reflected from ceiling, wall, or tabletop, or it may be emitted from a VDT screen. * Lumious contrast ratio describes the difference between the luminance values of two adjacent areas, assuming that there is a defined boundary between them.
Luminance counts The quantity that determines human vision is the luminance impinging on the retina. Luminance results from the light energy emitted or reflected from the visual target and from its visual surroundings in our field of view. In rooms, most light energy that reaches the eyes is that reflected from surfaces- mostly walls and ceilings. Excessive luminance often glares.
Glare
Polished surfaces reflect incoming light at the same angle at which it was received. Mirrors have a background coating that absorbs little light and reflects nearly all the incoming energy. The reflectance of a surface indicates the portion of incident light that is reflected by the surface. To avoid specular glare, surfaces can be made matte by giving them a rough surface that reflects in coming light in various directions.
Contrast
The larger the luminous contrast between two (reflecting or emitting) areas and the better defined their common boundary, the easier it is for the eye to distinguish them.
Room Surfaces The distribution of light within a room depends on the location of light sources and the direction of light flow from them, as well as on the reflectances of the ceiling, walls, and other surfaces. As a rule, the reflectances and colors of the room surfaces should be chosen so that there is a continuous decrease in reflectance from the ceiling to the floor. The ceiling reflectance should be about 80 to 90 percent-accomplished for instance, by white paint. The walls should have reflectances of 40 to 60 percent, which corresponds to bright beige, yellow or green. The floors should have a reflectance of approximately 20 to 40 percent, such as by medium blue-green or brown-beige colors. The surfaces of furniture and equipment should reflect at 25 to 45 percent.
Avoid glare from computer screen One speaks of “indirect” glare at the computer workstation if a light source is reflected from the monitor screen into the eyes, in much the same way as a window, a lamp, or a white shirt is reflected in a mirror. The reflected bright spot or surface on the screen reduces the contrast between background and displayed characters. The attempt to discern characters can lead to “eye fatigue”. A similar irritating condition called “direct” glare is caused by an intensive light source that shines directly into the eyes of the computer operator, generating high illumination of the retina, making it difficult for the rods and cones to discern contrast between characters and their background on the screen. Two other glare conditions are washout or veiling of the contrast on the screen and stray glare. Washout is caused by high ambient illumination; stray glare is caused by reflection from shiny surfaces in the field of vision.
Windows
Windows, liked by so many people, often generate difficult lightning conditions for the designer. On a bright day they are sources of high intensity and strongly directed light, able to generate both direct and indirect glare. Several means of controlling the light coming from a window can be employed: * The window panes may be colored dark to reduce the amount of illumination coming through. * Horizontal or vertical louvers can keep the light out. Vertical blinds are best when the sun low, horizontal blinds when the sun is high. Properly adjusted, blinds can screen out the direct rays of the sun, but still allow people to look out through the window. Also, blinds can be removed if not needed. * Curtains can be used to hinder direct sunlight from entering the room. Light-colored curtains absorb little energy from sunlight and hence do not heat up and then send warmth into the room, but they are highly luminous and thus may generate a source of high intensity. Therefore, with respect to light control, dark-colored curtains are preferred.
LIGHTING
The combination of different light sources contributes to a lighting concept that can be adapted to the different light requirements. The use of direct and indirect lighting in addition to a balanced day- and artificial light, is very important. On the one hand, in offices and at computer work stations a very high level of indirect lighting is recommended to support non-glaring. On the other hand, direct lighting provides the essential shadiness for a good illumination. That is the reason why combining both illumination techniques is vital. For such spot lightning, often called task lightning, a couple of arrangement can be used: The task luminaire may be mounted in the ceiling and shine a spotlight at the target; or, more commonly, a lamp is places near the source document directed at it. Care should be taken that the light source and the lighted surface do not generate direct or indirect glare for the operator or anyone else nearby. Also, it is necessary to use appropriate bulbs for right illumination (general lighting), as they support the task lighting in the room. Lights with a movable luminaire head are highly recommended for a suitable lighting at the workplace. When both computer-assisted and other tasks have to be managed from one workplace, individually placed table lamps serve as additional light sources. At some working places dimmable lights can also be advantageous.
Design for “No Bright Spots”
It is more effective to plan the layout of an office together with its illumination with an eye toward avoiding glare rather than counteracting existing glare conditions.

* The best solution is to install the proper light sources, because this eliminates direct and indirect glare at their points of origin. * The second best solution is to intercept the flow of light from a source to the eyes of the operator or to the screen, but this approach is usually more costly and less effective than installing the proper light sources. * The third and least desirable solution is to apply means at the display surface to reduce reflections and improve contrast, because most such treatments result in diminished visibility owing to the loss of the light energy.

Lenses to Correct Vision Defects Computer operators who experience vision difficulties and eyestrain often learn, upon taking a vision test, that they have eye deficiencies. To compensate, they need artificial lenses-eyeglasses or contact lenses. But using corrective lenses in correctly and generate new problems, particularly in the case of so-called reading glasses. These are ground for a viewing distance of about 40cm and a downward tilt of the line of sight, but many visual targets in the computer area are placed further away, including the screen, which, unfortunately, is too often placed well behind and above the keyboard. If such a visual target is beyond the focusing distance, one is tempted either to squint the eyes while crying to focus or to move the head forward to bring it closer to the correct focusing distance The first attempt may lead to “eye fatigue”, the second to improper neck posture and muscle tension. The effect is even more pronounced if one wears bifocals or trifocals, where the lowest section is meant for reading. In this case, one is likely to tilt the head severely backward in order to get the display on the screen on the “line of sight”, which the reading lense of the glasses determines to be downward with respect to the head. The ensuing strong backwards tilt of the head requires mascular tension and often results in a headache.
DESIGNING THE MOTOR INTERFACE
POSITION ON THE DESK
Place the keyboard as close to the front edge of the desk as is comfortable. Do not place documents between the keyboard and the front edge of the desk, as this increases the reach distance to the keyboard and may result in excessive bending of the neck to look at the documents. Where possible, layout should be reorganized to bring frequently used objects closer to the user. POSITION OF YOUR MOUSE AND KEYBOARD Both these items are used frequently and should be located on the desk in the primary reach area.
Keyboards:
Touch typist should locate the keyboard close to the desk edge. Non touch typists should locate the keyboard around 10 cm in from the desk edge. This enables Desk space to rest the hands when not typing. Reduce the neck angle when looking between the keyboard and monitor.
Mouse
The elbow should remain bent when reaching for the mouse. The mouse should be located in the primary area. Your forearm should rest on the desk when you hand is on the mouse. It should glide over the desk when using the mouse. Train yourself to use a mouse with either hand. Learn keyboard short cuts for frequent mouse activities and reduced the use of the mouse When mainly using the mouse, locate it directly in front of you and use your other hand for minor keyboard corrections. Do not continue to grip the mouse, when it is not in use. Do not hover your hand over the mouse, rest it on the mouse or desk.

DESIGNING THE SIT-DOWN WORKSTATION
CHAIR
* SEAT SPAN : Height: The only inherent limitation to the size of the seat pan is that it should be short enough that the front edge does not press into the sensitive tissues near the knee. The height of the seat pan must be widely adjustable, preferably down to about 37 cm and up to 58 cm, or at least to 50 or 51 cm. Usually, the seat pan essentially flat, between 38 and 42 cm deep and at least 45 cm wide. Adjust chair height so the feet are comfortably flat on the floor, the thighs are approximately horizontal and the lower legs approximately vertical.

* BACK REST
Height: Move the backrest to locate the lumbar support to the curve of your lower back. Frequent posture changes encourages blood flow to different muscle groups which helps minimize back fatigue when sitting for prolonged periods. The backrest should be as large as can be accommodated at the workplace. This means up to 85 cm high and at least 30 cm wide. The backrest should provide support from the head and neck on down to the lumbar region. The lumbar pad should be adjustable from 15 to 23 cm, a cervical pad from 50 to 70 cm, above the seat surface * ARM RESTS: Armrests are usually not recommended unless they are well out of the way of the desk. However, if your chair has arm rests make sure that they do not prevent you from getting as close to the desk as you require or that they impinge on your elbows while you are working. Armrests allow supporting the weight of the hands, arms, and even portions of the upper trunks.. They must be well located, with a suit able load-bearing surface. Adjustability in height, width, and, possibly, direction is desirable.

* FOOT RESTS: Use a foot rest if you feel pressure under your thighs from the front edge of your seat. A foot rest is also useful to address lower back fatigue when sitting for long periods. Pushing your feet into the foot rest helps to push your back into the angled back rest of the chair. If the seat pan cannot be sufficiently lowered for the seated person, then a footrest is needed. Footrest should not consist of a single bar or another very small surface, because this severely limits the ability of the sitting person to change the posture of the legs.

DESIGNING THE STAND-UP WORKSTATION
Stand up workstations can often use a spare computer in the office, to which work activities can be switched from the sit-down workstation for a while; or one may stand while reading, writing, or telephoning. Workplace design should accommodate the variety of employee shapes and sizes and provide support for the completion of different tasks. Work should be organized so that the employee has some choice about his/her working position and be given the opportunity to change position frequently.
Floor Surfaces If the surface of the floor is concrete or metal, anti-fatigue matting should be provided at the workstations. * Ensure that the matting has a sloped or beveled edge to avoid a tripping hazard. * When installing anti-fatigue matting, be sure to consider the application in which it will be used and requirements such as chemical spill resistance, oil resistance, heat resistance, etc.
Footrests
At standing workstations, provide employees with either a sand-alone footrest or rail at least 4 to 6 inches high. Elevating a foot puts the arch (called "lordosis") back in the low back, combats fatigue, and helps in recovery.
Footwear
Your feet can only be as comfortable as the footwear permits. * Wear shoes that do not change the shape of your foot. * Choose shoes that provide a firm grip for the heel. If the back of the shoe is too wide or too soft, the foot will slip causing instability and soreness. * Wear shoes that allow freedom to move your toes. Pain and fatigue result if shoes are too narrow or too shallow. * Ensure that shoes have arch supports. Lack of arch support causes flattening of the feet. * Tighten the lace instep of your footwear firmly. This helps prevent the foot from slipping inside the shoes or boots. * Use padding under the tongue of the shoe or boot if you suffer from tenderness over the bones at the top of the foot. * Consider using shock-absorbing cushioned insoles when walking or standing on cement or metal floors.
THE ENVIRONMENT * Office layout – the office layout follow sound architectural design principles, providing enough room and privacy to the individual. Personal preferences and job attributes may suggest either a separate room or cubicle or an open layout (“office landscape”) to facilitate communication with coworkers. * Static Electricity in the Office – static electricity may be a problem, not only because it can be irritating and may cause skin rashes in some operator, but also because it attracts dust to the screen. Proper material especially of carpets, grounding, and increased humidity of the room air can help solve the problem. * Sound in the Office – noise is usually not a major concern, since most computers operate at fairly low sound levels. However, a fan or printer may need attention. Background noise and interference from other workstations or equipment must be considered. The general recommendation is to keep the sound levels as low as possible, such as 60 dBA. * Light in the Office – the illumination level at the computer workstation is lower than that required in ordinary offices. The reasons are that reflections on the screen (glare) must be avoided and that the screen is itself a source of light which must be frequently viewed by the operator. Therefore, the general room illumination should be between 300 and 700 lx, with the lower levels appropriate when the hard copy (paper source document) used is of high quality (good contrast). If it is difficult to read the source document at low level illumination, a lamp may be used that shines exclusively upon the copy. The distribution of the illumination should be fairly constant throughout (with the exception of the spotlighted area) and should be either diffuse or directed so that there are no reflections on the screen. Wall and ceiling colors affect the absorption and reflection of light, as has been discussed, but otherwise are a matter of personal preference. * Climate in the Office – temperature can be a problem at some computer workstations where the equipment emits heat. The same requirements as in other offices apply, meaning that the effective temperature should be in the low (20 degrees Celsius) region, the relative humidity around 50%, and the air movement low, such as 0.5 m/s. Small deviations from these values should have no effects on the production or well-being of the office workers, but complaints about the office being too hot or cold are frequent in the United States. *
CHANGES THROUGH TECHNICAL DEVELOPMENTS
Flat panel display technologies include light-emitting diode (LED), liquid crystal display ( LCD ), and gas plasma. LED and gas plasma work by lighting up display screen positions based on the voltages at different grid intersections. LCDs work by blocking light rather than creating it. LCDs require far less energy than LED and gas plasma technologies and are currently the primary technology for notebook and other mobile computers are some of the new technology brought about by the some technical development. Clever software offers possibilities for facilitating the task of the computer operator. Among such software are automated programs for grammar and spelling, programs for stringing characters together, and algorithms that check and indicate outliers in data, unusual events, and repetitive occurrences. Certainly, a wide variety of opportunities exist to improve and facilitate the work of the computer operator

JOB CONTENT AND WORK ORGANIZATION The ability to received direct feedback about one’s work, preferably through a daily review supplemented by constructive comments from the supervisor, contributes significantly to the feeling of achievement and satisfaction. Within the limitations set by the requirement that certain work needs to be done, the operator should be free to distribute the workload, both in amount and pace, according to his or her own preferences and needs. Communicating with colleagues and maintaining social relations are essential, although the intensity of each varies with the individual. Isolating people or submitting them to cold, formal relationships is usually detrimental to their well-being and performance.
Flexibility in the attitude of management and in one’s work organization gives the individual latitude in the way a task is performed, the manner in which furniture is used, and how the workplace is arranged. Indeed, providing freedom for individual variations from the conventional norm acknowledge that persons in the office dinner in their physiques and work preference