Evaluating and Redesigning Workstations

Workstations should be ergonomically designed to accommodate the full range of required movements among workers. They should be designed to accommodate the workers who are actually using them to perform the job, not just for the "average" or "typical" worker. Many workstations, particularly those in factories, were designed for men, even though they may be primarily used by women.

The workstation should be designed to permit the worker to adopt several different but equally healthful and safe postures that still permit performance of the job; sufficient space should be provided for the knees and feet. Work tables and chairs should be height-adjustable to provide proper back and leg support. Seat cushions can be used to compensate for height variation when chairs or stools are not adjustable. Tools and materials should have a definite and fixed space for storage. Machine controls should be reachable and equally accessible by both right- and left-handed operators.

When evaluating or redesigning a workstation, give special attention to the following items:

• Static loading of muscles (prolonged or sustained exertion of a body part without movement) causes rapid fatiguing of the muscles. Requiring a worker to constantly hold a tool, even when not in use, is a good example of static loading.

• Proper work activity height can help control postural risk. Activity height can be adjusted by providing an adjustable work surface; by lowering the work surface and placing the work piece in a fixture that raises it to a proper height; or by raising the worker to the work surface.

• The reach at which tasks are performed affects the strength, precision capability, stress, and other biomechanical aspects of the worker. Therefore, maximum reach distance should be kept within the normal reaching distance, somewhere between 14 and 18 inches. The distance depends on the difficulty of the task, the forces exerted, and the frequency of the activity. Reaches above the shoulder, behind the worker, and far in front or to the side of the worker should be avoided.

• Force requirements should be reduced or minimized when possible. The worker should not be required to exert high forces. Work can often be performed more efficiently and more safely by providing a mechanical advantage, so mechanical solutions should be incorporated into the work station when possible. If workers are required to exert high forces, the work piece should be located and stabilized so that the forces are optimal and minimized. Force can sometimes be reduced by using fixtures and proper workstation height.

• Hard or sharp edges can be a hazard in a workstation. When the worker's arm or hand repeatedly comes in contact with a hard or sharp edge, damage to the tissues, including nerve or blood vessel damage, can result. Control measures include rounding edges, padding edges, or relocating equipment so people will not hit the edges.

• Contact with thermally conducting work surfaces can be responsible for loss of heat in the hands and arms. This can cause discomfort and, if the wrist and fingers become cold, the tendons and joints become stiff. This may cause symptoms of cumulative trauma disorders to develop.

• Proper seating should be made available to workers where the job permits. This is possible in many jobs where tradition has dictated that standing is the only way to do the job. It is also important to provide support for the limbs, both arms and legs. Arm and footrests help to reduce worker stress and fatigue.

• Work piece orientation can cause numerous problems, including higher than necessary repetitions, higher than necessary forces, and static and awkward postures. Care should be taken to ensure that the work piece is in such a position that the required tasks do not expose the workers to unnecessary hazards. Proper workstation height and proper fixtures and orientation devices can reduce or eliminate this problem.

• Work piece holding is a simple solution to ergonomic hazards which is often overlooked. Fixtures that hold the work piece and orient it for ease of work can greatly reduce the stress of the job and often increase productivity.

• Layout of a workstation has an impact on all of the preceding points of workstation design. A good layout will facilitate the flow of materials and product through the station.