The Journal of Science of Labour
Online ISSN : 2187-2570
Print ISSN : 0022-443X
Original Articles
A critical comment on the physiological entity theory of human fatigue from a viewpoint of workers’ fatigue study
Yoshio SAITO
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2016 Volume 92 Issue 1-2 Pages 1-16


In more than 100 years of the history of human fatigue study, there had been proposed several study methods, the first of which was named the physiological entity theory of human fatigue. This theory was established on the basis of results of physiological experimental studies at the beginning of the 20th century.
It was asserted in the theory that human fatigue should be physiologically defined and assessed, depending on physiological mechanisms on accumulation of metabolites such as lactic acid due to activity, depletion of substances necessary for activity and so on.
The theory hypothesized that an industrial worker's fatigue was a condition caused by work, in which his/her work capacity was diminished, inevitably resulting in a decrease in work performance, and that the diminution of the work capacity should be due to the functions of the physiological mechanisms.
The purpose of the present paper was to make clear the reason why it had been found out in the history of workers’ fatigue studies that the physiological entity theory was not applicable to the studies, with making reference to Muscio (1921) and Browne (1954).
The present paper discussed that studies on workers' fatigue had adduced evidence that when they continued to work in different types of tasks, their work performance increased or decreased, affected by psychological functions such as motivation, need and emotion. It was also discussed that the studies had proved it effective in reducing their fatigue to take measures to decrease long hours of work, to introduce adequate rest pauses, to improve work environmental factors such as illumination, temperature and noise, to make better design of a machine and equipment in a workplace, and so on.
The author of the present paper admitted that at the end of the first half of the 20th century, it was proved that the physiological entity theory of human fatigue was not able to assess work performance of industrial workers in actual workplaces, and therefore, that it was invalid for the explanation of the cause of their fatigue.

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© 2016 The Institute for Science of Labour
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