On the Natural Laws of Muscular Exertion

Abstract

AMONG a multitude of profound and happy suggestions to be found in Mr. Babbage's Economy of Manufactures, are some remarks on the relation between fatigue and the rapidity or degree of muscular exertion. Coulomb, it appears, had previously investigated the most favourable load for a porter, and had ascertained by experiment that a man walking upstairs without any load, and raising his burden by means of his own weight in descending, could do as much work in one day as four men employed in the ordinary way with the most favourable load. Mr. Babbage clearly points out (p. 30) that the exertion necessary to accomplish any kind of work consists partly of that necessary to move a limb of the body, and partly of the force actually utilised in the work. The heavier the work done, the larger the proportion, therefore, of the power utilised. But there is a limit to this mode of increasing the useful effect, because, by the natural constitution of the muscles, they can only develop a limited amount of force in a given time, and the fatigue rapidly increases with the intensity and rapidity of exertion. Hence there is in every kind of work a point of maximum efficiency, which is in practice ascertained more or less exactly by frequent trial.