In 1923, in a paper called "Physiology of Exercise,"1 we presented the results of a study of the physical capacity of children by means of a stationary bicycle. It was then pointed out that a considerable number of supposedly normal children fell below the average in physical strength and endurance. This striking observation led us to an inquiry into the psychophysiologic aspects of general subefficiency. The results were published in a paper called "Chronic Fatigue in the School Child: A Psycho-Physiologic Study."2
Since clinical methods of investigation offer little hope for the understanding of the nature of fatigue, we undertook to study this subject in animals. In this paper, we shall discuss the effect of forced exercise on (1) the voluntary activity, (2) the weight and (3) the behavior of rats.
MATERIAL AND EXPERIMENTAL PROCEDURE
Twenty male hooded rats, about 90 days of age, weighing on an average