ABSTRACT
111. Generalities.—From the point of view of utility, the energetic expenditure of man is that which corresponds to muscular activity only, but under certain circumstances, the muscles remain contracted without performing any work, in the mechanical sense of the word. The static effort thus expended causes a consumption of energy, and can be regarded as similiar to frictional work (§ 60) or vibratory work (§ 90). But the contraction develops some force ; dynamically it has variable degrees of speed and duration, its visible result being fatigue, which is itself susceptible to variation. If, however, only the kinds of activity which do not cause excessive fatigue are considered, then without forcing the muscles, it will be possible to estimate the amount of work according to the amount of energy expended. The one will increase with the other. In the variations of the expenditure will be seen the effect of the dynamic factors, force and speed, when the work done remains constant. It will also be seen how much the nature of the nutriment itself modifies the value of the expenditure.
