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Ergonomics is the science of fitting the job to the worker and adapting the work environment to the needs of humans. An overall goal of ergonomics is to promote health and safety and to optimize productivity.

The term ergonomics comes from the Greek words ergon, meaning "work", and nomos, meaning "laws"—thus, laws of work. The study of ergonomics as a way to reduce human error began in the military during the Korean War. In planes used for pilot training, the eject button was poorly placed and pilots sometimes accidentally ejected themselves—often at too low an altitude for their parachutes to open. The button's location was changed and fewer lives were lost.

Principles of ergonomics are now applied to the design of many elements of everyday life, from car seats to garden tools. Many different occupations are involved in implementing these "human factor" principles in the workplace, such as human factors/ergonomics specialists; safety engineers; industrial hygienists, engineers, designers; human resource managers; occupational medicine physicians and therapists; and chiropractors. Research in ergonomics is ongoing.

Knowledge of basic ergonomics principles is important for both workers and employers because both share responsibility for a safe work environment. One can easily imagine the potential hazards in manufacturing settings where equipment is operated and heavy materials are handled, but hazards exist in other environments, too. And technology (especially computer use) has brought about widespread changes in how work is accomplished.

Attention to ergonomics principles helps to reduce workplace injuries and illnesses that result in workers' compensation costs, medical claims, and lost work time. Many disorders and injuries are preventable when work conditions are designed for human safety and comfort. People need training in how to recognize hazards and safety problems as well as how to control their own behaviors for maximum comfort and health.

One of the key considerations in ergonomics is adjustability of physical elements. People come in all shapes and sizes, and the "average" workstation configuration will not fit everyone. Making changes during a workday in the physical setup of equipment, such as adjusting chair height, can alleviate discomfort and fatigue. Work surfaces should be at comfortable heights in relationship to a chair or to a standing position. Equipment and related items should be arranged conveniently.

Whenever a mismatch occurs between the physical requirements of a job and the physical capacity of a worker, musculoskeletal disorders can result. People working with intense concentration or at high speeds often work with poor posture. Cumulative trauma disorders (also called repetitive strain injuries) are caused by repeating the same motion in awkward positions or with noticeable force, such as in lifting heavy objects. Carpal-tunnel syndrome, a disorder affecting nerves in the wrist that has the potential to permanently disable, is a condition affecting people in a variety of occupations from meatpackers to musicians. Wrist pain can be severe, with treatment involving wrist splints, anti-inflammatory drugs, or even surgery. And people who use a computer extensively are especially prone to developing carpal-tunnel syndrome. Computer use often contributes to vision problems, too.

Posture in standing and in seated positions is important to avoid musculoskeletal disorders. The natural curve of the spine should be maintained, with the head balanced over the spine. When a person is seated:

• Feet should rest on the floor, with legs and body forming 90 to 110 angles.
• The body should be straight, with the neck upright and supporting the head balanced on the spine (not forward or twisted to the sides).
• Upper arms should be perpendicular to the floor; forearms should parallel the floor.

Symptoms of musculoskeletal disorders can begin as numbness or stiffness in joints or tingling, aching sensations in muscles. Pain or burning sensations may be evident, too. Often symptoms progress gradually, becoming more severe with prolonged exposure to the condition causing them. Damage to nerves, tendons, joints, or soft tissue can result.

With computer use so prevalent, poor work habits will contribute to musculoskeletal disorders for many people who spend long hours seated at a computer. These include the following:

• Wrists misaligned or excessive force used with a keyboard
• Poor posture used with an incorrect seating height
• A monitor incorrectly positioned, resulting in eye strain and vision problems
• Inappropriate lighting, causing glare on monitors and other work surfaces
• High concentration, causing infrequent breaks

The following paragraphs provide a few guidelines for working conditions when using a computer.

Chair: A well-designed chair with easy-to-implement adjustability is essential. A user can vary angles of back support and the seat pan to control the degree of pressure on the thighs and back. Weight should be evenly distributed, with no extreme pressure points. An upright posture is a little easier to achieve if the seat pan is tilted slightly forward of horizontal. When a person is seated, feet should rest on the floor and the chair seat pan should be even with the back of the knee, ranging from 13 to 19 inches above the floor depending on an individual's height. A foot rest may be used to relieve pressure on the thighs. Both lumbar and mid-level back support are needed. Arm rests, adjustable for height, are helpful to many people. The chair should have a five-point base for stability and casters for easy movement.

Keyboard : The keyboard provides the primary means of interacting with a computer. The keyboard should be in a comfortable position, and wrists should "float" over the keyboard when keying with a light touch so wrists and forearms remain straight. Although wrist pads are helpful for resting when not keying, they can actually create problems when a user keeps wrists on them when keying because the wrists can bend down. Different opinions exist on the appropriate angle of the keyboard; some people prefer a flat position while others find a reverse incline more comfortable. Split and curved key boards are available, too. However, the most important part of keyboard use is keeping the wrists straight in line with the forearm and not bent to the side. When voice-recognition technology be comes commonly used, dependency on the key board will be reduced.

Mouse : A mouse should be positioned next to the keyboard, reachable without extending the arm in an awkward position. Again, a light touch is needed and users should avoid gripping or squeezing the mouse. A wrist support or adjustable mouse platform may be helpful if a user begins to develop wrist problems. A variety of shapes are available for these pointing devices, and a trackball can be used for the same purpose.

Monitor : A monitor should be directly in front of the user, with the top of the screen at or below the line of sight, 18 to 30 inches away from the eyes, and tiltable to avoid glare from overhead lighting and windows. If necessary, antiglare filters can be added. Screen size should be large enough for easy reading of screen character sizes with a screen refresh rate fast enough to avoid a visible flicker. An individual can experience blurred vision or fatigue from a poor monitor viewing angle, reflected glare, or a low-quality monitor. Because glands in the eyelids produce tears that cleanse eyes as the eyelids blink and the eyes move, irritated eyes can develop because one's blink rate tends to decrease when one is concentrating.

To avoid neck and eyestrain, an individual should do the following:

• Use a copyholder positioned near the monitor to support material used with computer work.
• Use lower levels of lighting to reduce glare on monitors. Many older offices have high illumination levels that are necessary for paper-intensive tasks—but are too highly lighted for computer work. Softer overall, or ambient, lighting should be used, with task lighting added to surfaces as needed for more illumination.
• Relax eye muscles by shifting focus from the computer screen to distant objects for a few seconds every 5 to 10 minutes.
• Take micro breaks to stretch the neck, shoulders, hands, wrists, back, and legs as well as to rest the eyes. Stretching exercises can be simple neck rotations, shoulder shrugs, fists clenched and then released, or arms hanging down naturally for a few moments. Get up and move around about every 30 minutes. Take a brisk walk if possible. Exercises with hand weights will help with stretching and will give the body isometric exercise.

While it may be ideal to have individually adjustable temperature controls, this is not feasible in many work situations. For business offices, most people are comfortable with temperature levels at 68 to 72 in the winter and 72 to 76 in the summer. Humidity levels should be maintained between 40 to 60 percent not only for comfort but also for proper functioning of office equipment. Indoor air quality involves more than heating and cooling—air should be cleansed of pollutants (bacteria, dust, fumes, etc.), with fresh air added before circulation. Many factors affect the efficiency of HVAC (heating, ventilation, and air conditioning) systems. These systems must be designed for the number of people and the equipment to be used in each area because computers and other devices can produce almost as much heat as a human body produces.

Another important concept is adjustability of work pace. Jobs may require redesign to allow workers to accomplish tasks at varying speeds or to enable workers to rotate to different tasks or to use a variety of work methods that permit different movements. Rest breaks are important, too, and microbreaks can be taken to interrupt in tense situations, to rest arms and wrists, or to rest eyes.

Much ergonomics information is available in print and on the Internet, published by organizations such as the Occupational Safety and Health Administration (OSHA), the National Institute of Occupational Safety and Health (NIOSH), the National Safety Council, the Human Factors and Ergonomic Society, and others. OSHA is developing ergonomics program standards that were to be published in 2000 (OSHA 1999). Consultants can provide technical expertise to help with all phases of ergonomics assessment and the implementation of corrective measures and/or training programs.