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Wednesday, 12 January 2011 19:57

Ergonomic Factors

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The purpose of this article is to afford the reader an understanding of how ergonomic conditions can affect the psychosocial aspects of working, employee satisfaction with the work environment, and employee health and well-being. The major thesis is that, with respect to physical surroundings, job demands and technological factors, improper design of the work environment and job activities can cause adverse employee perceptions, psychological stress and health problems (Smith and Sainfort 1989; Cooper and Marshall 1976).

Industrial ergonomics is the science of fitting the work environment and job activities to the capabilities, dimensions and needs of people. Ergonomics deals with the physical work environment, tools and technology design, workstation design, job demands and physiological and biomechanical loading on the body. Its goal is to increase the degree of fit among the employees, the environments in which they work, their tools and their job demands. When the fit is poor, stress and health problems can occur. The many relationships between the demands of the job and psychological distress are discussed elsewhere in this chapter as well as in Smith and Sainfort (1989), in which a definition is given of the balance theory of job stress and job design. Balance is the use of different aspects of job design to counteract job stressors. The concept of job balance is important in the examination of ergonomic considerations and health. For instance, the discomforts and disorders produced by poor ergonomic conditions can make an individual more susceptible to job stress and psychological disorders, or can intensify the somatic effects of job stress.

As spelled out by Smith and Sainfort (1989), there are various sources of job stress, including

  1. job demands such as high workload and work pace
  2. poor job content factors that produce boredom and lack of meaningfulness
  3. limited job control or decision latitude
  4. organizational policies and procedures that alienate the workforce
  5. supervisory style affecting participation and socialization
  6. environmental contamination
  7. technology factors
  8. ergonomic conditions.


Smith (1987) and Cooper and Marshall (1976) discuss the characteristics of the workplace that can cause psychological stress. These include improper workload, heavy work pressure, hostile environment, role ambiguity, lack of challenging tasks, cognitive overload, poor supervisory relations, lack of task control or decision-making authority, poor relationship with other employees and lack of social support from supervisors, fellow employees and family.

Adverse ergonomic characteristics of work can cause visual, muscular and psychological disturbances such as visual fatigue, eye strain, sore eyes, headaches, fatigue, muscle soreness, cumulative trauma disorders, back disorders, psychological tension, anxiety and depression. Sometimes these effects are temporary and may disappear when the individual is removed from work or given an opportunity to rest at work, or when the design of the work environment is improved. When exposure to poor ergonomic conditions is chronic, then the effects can become permanent. Visual and muscular disturbances, and aches and pains can induce anxiety in employees. The result may be psychological stress or an exacerbation of the stress effects of other adverse working conditions that cause stress. Visual and musculoskeletal disorders that lead to a loss of function and disability can lead to anxiety, depression, anger and melancholy. There is a synergistic relationship among the disorders caused by ergonomic misfit, so that a circular effect is created in which visual or muscular discomfort generates more psychological stress, which then leads to a greater sensitivity in pain perception in the eyes and muscles, which leads to more stress and so on.

Smith and Sainfort (1989) have defined five elements of the work system that are significant in the design of work that relate to the causes and control of stress. These are: (1) the person; (2) the physical work environment; (3) tasks; (4) technology; and (5) work organization. All but the person are discussed.

Physical Work Environment

The physical work environment produces sensory demands which affect an employee’s ability to see, hear and touch properly, and includes such features as air quality, temperature and humidity. In addition, noise is one of the most prominent of the ergonomic conditions that produce stress (Cohen and Spacapan 1983). When physical working conditions produce a “poor fit” with employees’ needs and capabilities, generalized fatigue, sensory fatigue and performance frustration are the result. Such conditions can lead to psychological stress (Grandjean 1968).

Technology and Workstation Factors

Various aspects of technology have proved troublesome for employees, including incompatible controls and displays, poor response characteristics of controls, displays with poor sensory sensitivity, difficulty in operating characteristics of the technology, equipment that impairs employee performance and equipment breakdowns (Sanders and McCormick 1993; Smith et al. 1992a). Research has shown that employees with such problems report more physical and psychological stress (Smith and Sainfort 1989; Sauter, Dainoff and Smith 1990).


Two very critical ergonomic task factors that have been tied to job stress are heavy workloads and work pressure (Cooper and Smith 1985). Too much or too little work produces stress, as does unwanted overtime work. When employees must work under time pressure, for example, to meet deadlines or when the workload is unrelentingly high, then stress is also high. Other critical task factors that have been tied to stress are machine pacing of the work process, a lack of cognitive content of the job tasks and low task control. From an ergonomic perspective, workloads should be established using scientific methods of time and motion evaluation (ILO 1986), and not be set by other criteria such as economic need to recover capital investment or by the capacity of the technology.

Organizational Factors

Three ergonomic aspects of the management of the work process have been identified as conditions that can lead to employee psychological stress. These are shift work, machine-paced work or assembly-line work, and unwanted overtime (Smith 1987). Shift work has been shown to disrupt biological rhythms and basic physiological functioning (Tepas and Monk 1987; Monk and Tepas 1985). Machine-paced work or assembly-line work that produces short-cycle tasks with little cognitive content and low employee control over the process leads to stress (Sauter, Hurrell and Cooper 1989). Unwanted overtime can lead to employee fatigue and to adverse psychological reactions such as anger and mood disturbances (Smith 1987). Machine-paced work, unwanted overtime and perceived lack of control over work activities have also been linked to mass psychogenic illness (Colligan 1985).


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