Basic Ergonomic Principles

Bernardino Ramazzini was an Italian physician born in 1663 who is considered to be the founder of occupational and industrial medicine. In 1700 he wrote De morbis artificum diatribe (Diseases of Workers). This study of 52 occupations outlined material and handling hazards as well as “certain violent and irregular motions and unnatural postures of the body, by reason of which the natural structure of the vital machine is so impaired that serious diseases gradually develop therefrom” (currently defined as repetitive strain injuries or cumulative trauma disorders). Ramazzini’s work laid the groundwork for advocacy of protective measures for workers and encouraged eventual passage of factory safety and workmen’s compensation laws.

(Source: Ramazinni, B., 1717 and 1940, In W. Wright (trans.): The Disease of Workers, (

Chicago

University

Chicago

Press).

Wojciech Jastrzebowski was a Polish biologist who coined the term “ergonomics” in 1857. The word comes from two Greek words: ergon (work) and nomos (laws). Ergonomics is often defined as the practice of designing the job to fit the worker, not forcing the worker to fit the job. With the advent of the industrial age in the early 1900’s, “Scientific Management” applied ergonomic concepts with the goal of improving worker productivity and efficiency. And during World War II, the use of ergonomic principles flourished when it was shown that these principles could be used to reduce operator and pilot error on the emerging, complex war machinery.

Currently, the focus of ergonomics is to minimize work stressors, both physical and environmental to reduce the potential for bodily harm. These work stressors were clearly outlined in Ramazzini’s works.

The basic work stressors that promote repetitive or cumulative injuries include excessive repetition, forceful movements, and awkward movements and postures. General ergonomic principles help us to control these work stressors.

Repetitive tasks may not require much muscular effort, but the velocity and range of the movements can cause muscles to fatigue quickly as the muscle never completely relaxes and never completely contracts. With insufficient rest time, recovery of micro-trauma to the muscles, tendons and joints is not complete. Gradually, injury builds until swelling and pain begin to limit activity.
Forceful movements require excessive tension or pressure on the tissues of the body, increasing muscular effort, reducing circulation to the body’s tissues, and causing muscles to rapidly fatigue.
Awkward movements and postures place biomechanical stresses on the joints, muscles and tendons, causing friction and inflammation at the stressed sites, reducing the body’s ability to perform work efficiently and comfortably.

In these articles, some common-sense tips are offered- based on the ergonomic principles of avoiding repetition, force and awkward postures - to help make work less stressful on the body.

Marji Hajic is an Occupational Therapist and a Certified Hand Therapist practicing in Santa Barbara, California. For more information on hand and upper extremity injuries, prevention and recovery, visit Hand Health Resources.