METHODS AND APPARATUS 21 
and carbohydrates for muscular work, but the apparatus was chiefly used as 
a means of securing a large and accurately known amount of muscular work. 
A description of this new form of bicycle ergometer was given in a publi- 
cation by Benedict and Carpenter which appeared in 1909. a The experiments 
reported in the same publication were primarily designed for the study of the 
efficiency of the body as a machine, and included a series of experiments with 
a professional bicycle rider in which an enormous amount of external muscular 
work was performed by means of this ergometer. In the calibration of the 
apparatus certain abnormal factors were observed which ultimately became 
the subject of a special investigation b in which the influence on the magnetic 
field of the rotation of a copper disk was accurately studied. In this research, 
two ergometers constructed upon the same principle were observed; these in- 
struments were, as a matter of fact, those subsequently employed for the study 
of the metabolism during muscular work which is reported in this publication. 
METHODS AND APPARATUS USED IN THIS RESEARCH. 
GENERAL PLAN OF THE RESEARCH. 
A critical examination of all the literature bearing upon the relationship 
of muscular work and metabolism brings out two striking facts: 
First, that while many investigators have studied the influence of mus- 
cular work upon the character of the material katabolized in the body to find 
whether or not there is a selective combustion incidental to severe muscular 
activity, it nevertheless remains a fact that there is a wide diversity of opinion 
on the subject. 
Second, that the relationship between the actual amount of external 
work performed and the energy equivalent of the materials katabolized is 
by no means established, the results obtained by the various investigators 
differing within wide limits. 
Even in the more recent work, the divergence of opinion on both these 
points is very noticeable. Thus, Chauveau and the members of the French 
school are strongly inclined to maintain that there is a selective combustion 
of carbohydrate material during muscular work. On the other hand, Zuntz 
and his associates are thoroughly convinced that muscular work does not alter 
the character of the metabolism. Similarly, in discussing the efficiency of the 
body as a machine, the values found by the French investigators are notice- 
ably different from those of Zuntz and his associates, and there is likewise a 
wide difference between the values found with the respiration chamber at 
Middletown, Connecticut, which have been reported by Benedict and Car- 
penter, and those of Zuntz and Durig and their associates. 
An examination of the experiments made in this laboratory for a number 
of years past shows that the diversity of results obtained and reported by 
other investigators has not been observed here, since our values indicate in a 
general way a uniformity in the effect of muscular work upon metabolism. 
In view of the development of an extremely accurate bicycle ergometer which 
o Benedict and Carpenter, U. S. Dept. Agr., Office Expt. Stas. Bui. 208, 1909, p. 11. 
6 Benedict and Cady, Carnegie Institution of Washington Publication No. 167, 1912. 
