43^ Muscular Work and the Respiratory Quotient [April-July 



der Biochemie^ Prof. Zuntz defends the thesis that all body mate- 

 rials can yield energy to the working muscle. 



The Carnegie Institution of Washington recently published a 

 monograph by F. G. Benedict and E. P. Cathcart,* dealing with the 

 metabolism of muscular work, which is of the utmost interest as a 

 very noteworthy contribution to an acutely debated subject. Besides, 

 the scientific reputation of its authors, the perfection of the appa- 

 ratus for measuring the external work, and the unsurpassed re- 

 sources of the Carnegie Institution for experimental investigation, 

 vouch for the importance of the monograph. 



This monograph appears to offer substantial support to Chau- 

 veau's hypothesis. In practically all the work-experiments, the 

 respiratory quotient increased, attaining especially high values in 

 severe work. Respiratory quotients of i.oo, indicating pure carbo- 

 hydrate consumption, were not infrequent and in a number of ex- 

 periments it was even greater than i.oo. This last fact which, if 

 correct, implies a transformation of glycogen into fat as a result of 

 severe work, is so incredible that it seems necessary to assume that 

 some serious source of experimental error has been overlooked. A 

 scrutiny of the technic shows that this assumption is justified. 



The very high respiratory quotients were usually coincident with 

 rapid breathing on the part of the subject. Thus, in one series of 

 experiments, as the resistance was gradually increased, the rate o^ 

 respiration per min. changed from 18-22 to 36-40, while the respi- 

 ratory quotient also changed from 0.87 to i.oo. In another set of 

 work-experiments, the respiratory quotient was 0.80-0.83 during 

 light exertion, when the rate of respiration was 20-24 but, as the 

 work became more severe, the respiratory quotient increased to 

 0.97-1.03 and the respiration rate became 36-38 per min. We 

 know, of course, that both carbon dioxid and water vapor are given 

 off through the lungs and, under forced breathing, their absolute 

 quantities increase greatly. In the two sets of experiments just re- 

 ferred to, the carbon dioxid elimination increased 2 to 2.5 times and 

 exceeded 2.5 liters per min. No determination was made of the 

 amount of water expired during the same time but the quantity 

 must likewise have been much greater. Is it not possible that some 



1 Benedict and Cathcart: Muscular work; a metabolic study with special 

 reference to the efficiency of the human body as a machine. Pp. 176, 1913. 



