76 MUSCULAR WORK 
periments, the subject lying quietly upon a couch and the measurements 
being made as rapidly as possible in periods of 15 minutes each. The com- 
position of the alveolar air was also determined in this study of the after- 
effect of muscular work. The negative results of these observations will be 
discussed in a subsequent section of the report. 
THE BASAL METABOLISM. 
In many investigations on the influence of muscular work upon the metab- 
olism, as, for instance, in experiments in which mountain-climbing, march- 
ing, or other work outside of the laboratory was performed, it was frequently 
impossible to secure a value for the normal resting metabolism of the subject 
under conditions obtaining at the time that the muscular activity began or 
ended; it was therefore necessary to assume this value. There are, however, 
many factors which tend to alter the relative proportions of materials in the 
body, — the protein, the fat, and the carbohydrates, — and which thus ob- 
viously alter the basal metabolism. This is especially true in a research 
covering a long period. 
It is difficult to conceive of any factor which would alter in a short time 
the relative proportion of either the stored body-protein or the body-fat. 
Consequently we consider first the factors affecting the body composition 
which require considerable periods of time. These would include prolonged 
inanition, which would deplete carbohydrates and fat, rather than protein; 
training in any form of muscular activity, during which there would be a 
loss of subcutaneous fat with a hypertrophy of the muscles; fever, which 
would cause a great depletion of fat and also of protein; and obesity, in which 
there would be the addition of large amounts of subcutaneous fat. With the 
possible exception of very severe training, none of these would result in any 
material alteration in the storage of protein and fat in a period of less than a 
week. 
While the storage of protein and fat in the body is not readily altered, 
the storage of carbohydrates, on the other hand, being comparatively small, 
may be quickly depleted in 24 hours or perhaps in even less time. Of the 
factors known to affect rapidly the glycogen storage, none has been more 
definitely demonstrated than complete inanition, experiments made with 
fasting men showing a very rapid and extensive depletion of the carbohydrate 
storage. Thus it has been established that a fasting man may draw from the 
storage of carbohydrates in the body, chiefly glycogen, as much as 180 grams 
on the first day of fasting, while experiments made at Wesleyan University, 
Middletown, Connecticut, with 7 fasting men showed that on the first day 
of fasting there was an average katabolism of 110 grams of glycogen. Since 
it is commonly supposed that the total storage of glycogen or carbohydrates 
in the body is not far from 400 grams, 6 it can be seen that this is a relatively 
enormous depletion of the stored material. 
The preceding diet also has a great influence upon the storage of carbo- 
hydrates in the body, as indicated by the respiratory quotient. In experi- 
ments carried out in this laboratory c with diets containing in one period a 
large preponderance of carbohydrates and in another period a large prepon- 
a Benedict, Carnegie Institution of Washington Publication No. 77, 1907, p. 464. 
b For a discussion of this estimate see p. 96, this report. 
« Benedict and Higgins, Am. Journ. Physiol., 1912, 30, p. 217. 
