Efficiency Methods
An Introduction to Scientific Management

FATIGUE-STU DY 99 muscles is distributed, giving a general sense of weariness. These products must be eliminated before the weariness can disappear. Meanwhile, if the tired muscles are still used, greater energy is required to make them contract properly, and the fatigue-products accumulate at a greater rate. There is great waste of energy in continuing work after fatigue has set in. Whereas a rest of half an hour will be sufficient after a certain amount of exertion, twice that exertion will need more than an hour’s rest, very likely two hours. There is no simple proportion rule between exertion and rest. Therefore rest periods must come betimes, and not be postponed. The question of nervous fatigue is much more complex. Feelings of weariness, being partly ner- vous and partly muscular, cannot be taken as sure guides to the actual amount of fatigue. The estimation of actual amount of fatigue is not, indeed, a simple or direct matter. In industrial investigations two methods have been adopted to indicate numerically in some way the accumulation of fatigue. One is the diminution of output per hour; the other is the increase in the number of accidents per hour. It has been established, with at any rate a large degree of probability, that relaxed attention due to fatigue is responsible for a considerable number of accidents. Both methods show that fatigue usually sets in very notably after two or three hours’ consecutive work ; though it should be added that the nature of