Ergonomics or human factors is the scientific discipline concerned with the understanding of relations among humans and other elements of a system, and the profession that applies theory, principles, data and methods to design in order to optimize human comfort and overall system performance. Ergonomists add to the design and assessment of tasks, jobs, products, environments and systems in order to make them attuned with the needs, abilities and limitations of people (Helander, 2006). "Ergonomics is defined as the design of the workplace, equipment, machine, tool, product, environment, and system, taking into consideration the human's physical, physiological, biomechanical, and psychological capabilities, an optimizing the effectiveness and productivity of work systems while assuring the safety, health, and well-being of the workers" (Fernandez, 1995). In general, the aim in ergonomics is to fit the task to the individual person, not the individual person to the task.

Low back injuries, often due to improper manual handling of materials, form the largest subset of musculoskeletal injuries. The seriousness of the lower back injury problem is reflected in the large number of claims under the U.S. Worker's Compensation Act of 1970. The National Safety Council has reported that in the U.S.A. 400,000 workers face disabling back injuries every year. Statistics also show that back injuries resulting from manual materials handling (MMH) activities are a major source of lost time and compensation claims. Back injuries alone cost industry an estimated U.S.$14 billion a year (Fernandez, 1995).

In common with other industries,...

Following the introduction of the Manual Handling Operations Regulations in1992, members of the group have been involved in assessing and reducing the risks associated with all manual handling activities. There has been a concerted effort to eliminate all high risk tasks through the introduction of new and improved equipment and improved working methods. One of the keys to the success of this initiative was the breadth of operational knowledge within the ergonomics group and the way in which it worked with front line managers, staff and unions. This proved to be essential in arriving at realistic solutions which were both operationally and ergonomically acceptable (Dillon, 1999).
Manual letter sorting probably poses little risk for musculoskeletal disorders. Work on the automatic mail processing machines is potentially hazardous to employees due to design flaws and the high volume capacities of these machines. Under moderate mail volume conditions, the feeder positions on the OCR, BCS, and DBCS machines could be improved by providing a mechanism to reduce trunk flexion while retrieving trays of mail from the mail carriers. The sweep positions on the OCR and BCS machines could be made safer by redesigning the work station to reduce the amount of trunk flexion and arm reaching (HHE Report No. HETA-92-0073-2337, United States Postal Service, General Mail Facility, Denver, Colorado, 1993).

In December 1991, the National Institute for Occupational Safety and Health (NIOSH) received a confidential health…