Gilbreth (1911) holds the view that due to unsatisfactory and unsuitable working conditions, fatigue is caused and hence there is a daily loss of 20% workers due to decrease in production. Adverse effect is also found in the individuals and on the welfare of the society.
Health of Munitions Workers Committee defined fatigue as “the sum of the results of activity which show themselves in a diminished capacity for doing work”.
Muscio (1921)1 defines fatigue as “a condition caused by activity in which output produced by that activity tends to be relatively poor and the degree of fatigue tends to vary directly with the poorness of output”. Muscio, however, is not satisfied with this definition because fatigue cannot be directly measured and because diminished output may also be cause of distraction.
The most accepted definition of fatigue is “reduction in the ability to do work caused by changing in the chemical and psychological level”.
According to British Association Committee fatigue is“diminution of the capacity for work which follows excess of work or lack of rest and which is recognized on the subjective side by a characteristic malaise”.
According to Viteles2''. tension, speed, subjection to specification of work and a decrease in the enjoyment of work leads to fatigue”.
According to business directory, “employee burnout characterized by physical or emotional exhaustion, resulting in lowered job productivity and performance. The employee becomes tired of doing the job, which results in poor motivation. The fatigue may be caused by such factors as understaffing, unpleasant surroundings, and high pressure”.
In an intensive study called “Fatigue and hours of service of interstate truck drivers” (1941) the term fatigue is defined as an altered psychological and physiological state in relation to the states of recovery or normal capacity.
‘Fatigue is caused by length or intensity of some activity in a gainful occupation’, defined by Maier (1970)3.
Fatigue is a widely used term related to a physiological and psycho- logical state. Although it is given as a synonym for drowsiness and tiredness it is often mistakenly associated with sleepiness. Both, fatigue and sleepiness are characterized by a decrease in memory, reaction time, information processing, decision-making and vigilance, but one can be fatigued without being sleepy.4
Fatigue is considered an internal precondition for unsafe acts because it negatively affects the human operator’s internal state. Research has generally focused on pilots, truck drivers, and shift workers.