This book will outline a method of attack, and furnish a working practice for attacking the fatigue problem in an industrial plant. This practice is recommended because it rests on the results of measurement. We have here not simply a collection of illustrations that show what has been done in eliminating fatigue in the industries. All fatigue elimination is to be commended, but illustrations that do not embody well-recognized principles are questionable models. It is easy to make external changes that never touch the underlying cause of evil. Worthwhile, permanent fatigue elimination goes at the fundamentals of the work itself, and studies these in relation to the fatigue. _What_ has been done is worth while when we know _how_ it has been done, and _why_ it has been done. Given these facts, we can determine how it may be done again in the same fashion and possibly even better. The practice that is the result of _accurate measurement_,--this is the standard to be demanded. The Relation of Fatigue Study to Measured Functional Management. Fatigue study is founded on measurement. This makes it an integral part of measured functional management. This is management that acts in accordance with standards. These standards are derived by actually measuring accurately what is happening. Standards contain the results of the measurement combined into new working methods. These standards are maintained only until they can be improved, when the new ones are in turn measured and maintained. Such accurate measurement demands that the problem of management be divided into measurable units. These units are made as small as possible, and constantly smaller as time goes on. It was the great work of Doctor Taylor to divide an operation, that is, a piece of work to be measured, into units for timing with a stop watch, and to _separate rest units from work units_. From its beginning, Scientific Management has recognized the importance of the part played by fatigue. This recognition helps to obtain that co-operation and permanent beneficial efficiency that are the underlying ideas and the maintaining forces in this type of management. But fatigue study has only recently been acknowledged as fundamental to the most efficient management. Any one can attack the fatigue problem in its present condition in the industries successfully. He has simply to apply measurement. He can do this without regarding the investigations and results of others, if he chooses, but he will progress faster and farther if he uses results already at hand, and improves on “the best that has been known and thought in the world.” Relation of Fatigue Study to Motion Study.