The Classes of Fatigue.
There are two classes of fatigue:
1. Unnecessary fatigue, which results from unnecessary effort, or work which does not need to be done at all. A typical example of such work is that of the bricklayer, who furnished one of the first subjects for motion study. Any one who has watched a bricklayer lift all of his body above the waist, together with the bricks and mortar from the level of his feet to the top of a wall, cannot fail to realize that bricklaying requires a great amount of energy as well as skill. Yet by far the most of the energy expended in the method of laying bricks, that had existed for centuries, was entirely unnecessary.[2]
2. Necessary fatigue, which results from work that must be done. The new method, which enabled this same bricklayer to lay three hundred and fifty bricks per hour, where he had laid one hundred and twenty bricks per hour before, did not eliminate, and did not expect to eliminate all of the fatigue accumulated in the working day. The bricklayer at the end of the day, by reason of motion study devices, laid more brick, but was nevertheless much less tired. Experimental work in his case was carried to a high degree of perfection, because he was recognized as a splendid type of efficient brawn.