Ergonomics is the study of humans at work in order to understand the complex relationships among people, machines, job demands, and work methods in order to minimize gaps between task demands and human capacities in activities of work and daily living.1 All human activities, regardless of their nature, place both physical and mental demands on the worker. As long as these demands are kept within reasonable limits, performance will be satisfactory and health will be maintained. However, if stresses are excessive, undesirable outcomes may occur in the form of errors, accidents, injuries, and/or a decrement in health.
Occupational ergonomics is a discipline concerned with evaluating stresses that occur in the work environment and the ability of people to cope with these stresses. Its goal is to design facilities (e.g., factories and offices), furniture, equipment, tools, and job demands to be compatible with human dimensions, capabilities, and expectations. Ergonomics is a multidisciplinary science with four major areas of specialization:
Cognitive Ergonomics (sometimes called engineering psychology) is concerned with the information-processing requirements of work. Major applications include designing displays (e.g., gauges, warning buzzers, signs, instructions), controls (e.g., knobs, buttons, joysticks, steering wheels), and software to enhance human performance while minimizing the likelihood of error.2,3
Anthropometry is concerned with the measurement and statistical characterization of body size in the context of workplace and task dimensions. Anthropometric data provide important information to the designers of clothing, furniture, machines, tools, and workstations.4,5,6
Work Physiology is concerned with the responses of the cardiovascular system, pulmonary system, and skeletal muscles to the metabolic demands of work. This discipline is concerned with the prevention of whole body and/or localized fatigue that results from a mismatch between job demands and worker capacities.7
Biomechanics is concerned with the transfer of forces through the musculoskeletal system and the corresponding deformation of tissues.8 Many mechanical stresses can cause overt injuries (e.g., a concussion when a worker is struck in the head by a dropped object). In most cases, overt injury hazards are readily recognized and can be controlled through safety engineering techniques such as machine guarding and personal protective equipment.9 Other stresses are more subtle and can cause chronic or cumulative injuries and disorders. These stresses may be external (e.g., a vibrating tool that causes white finger syndrome) or internal (e.g., tension in a tendon when the attached muscle contracts).
This chapter is concerned primarily with physical work activities and prevention of work-related musculoskeletal disorders (WRMSDs). Typical examples of WRMSDs include:
A poultry worker develops numbness and tingling in the hand and fingers due to the repetitive hand motions associated with dismembering chickens.
A farm worker experiences pain in the lower back attributed to the awkward stooping posture required to harvest vegetables.
A nurse's aide suffers a back strain when transferring a patient from a hospital bed to a wheelchair.