GASEOUS EXCHANGE AND PHYSIOLOGICAL BE- 



QUIBEMENTS FOE LEVEL AND 



GEADE WALKING 



INTRODUCTION. 



This investigation was undertaken as a part of the larger plan 

 formulated in the Nutrition Laboratory some years ago for the study 

 of the energy requirements of the body during muscular exercise, 

 including a consideration of the efficiency with which the human body 

 can perform some of its more common daily tasks. The results of 

 Atwater and Benedict, 1 obtained in experiments with the respiration 

 calorimeter at Wesleyan University, demonstrated that the energy 

 of the human body could be measured like that of any machine. 

 Accordingly, when the Nutrition Laboratory was established in Boston, 

 the plans for research included a continuation of this work, and a res- 

 piration calorimeter was constructed, which was designed especially 

 for this type of experiment. 



The results of the studies of Zuntz 2 and his associates on the gaseous 

 exchange of the animal body demonstrate that the energy require- 

 ments can be found indirectly by computation from the oxygen con- 

 sumption and the respiratory quotient with an expenditure of much 

 less time and effort than is required for direct measurements by the 

 respiration calorimeter. This has resulted in a diminishing use of 

 the respiration calorimeter for the energy measurements of the human 

 body, and the data reported in the following pages have been obtained 

 by indirect calorimetry. However, it must not be overlooked that 

 the respiration calorimeter first demonstrated that the law of the 

 conservation of energy holds in the animal body and that for our 

 knowledge of the values used in indirect calorimetry we depend on 

 data obtained by direct calorimetric measurements. 



The numerous comparisons of direct and indirect calorimetry 

 made by Lusk and Du Bois in New York, with the calorimeter at the 

 Russell Sage Institute of Pathology, as well as those made with the 

 calorimeters at Wesleyan University and later at the Nutrition Labora- 

 tory, have shown that with severe muscular work the agreement 

 between the results obtained by the direct and indirect methods is 



J Atwater and Benedict, U. S. Dept. Agr., Office Exp. Sta. Bull. 69, 1S99; ibid, Bull. 109, 1902; 

 ibid. Bull. 136, 1903; Benedict and Milner, U. S. Dept. Agr., Office Exp. Sta. Bull. 175, 1907; 

 Benedict and Carpenter, U. S. Dept. Agr., Office Exp. Sta. Bull. 208, 1909. 



2 Zuntz, Archiv f. d. ges. Physiol., 1897, 68, p. 201. See, also, Zuntz and Schumburg, Physi- 

 ologie des Marsches, Berlin, 1901, p. 260. 



