METABOLISM WITH GRADE WALKING. 233 



ence of the Nutrition Laboratory is wholly in line with their question- 

 ing the use of the mouthpiece in researches involving specifically a 

 study of the respiratory quotient. Benedict and Murschhauser 1 

 emphasized the desirability of studjdng the metabolism during muscu- 

 lar work in a respiration chamber "with free breathing, without the 

 use of either mouth or nose appliances." This Krogh and Lindhard 

 have done with all of the niceties of detail characterizing Krogh's work. 

 It is a cause for regret that since they stress especially the respiratory 

 quotient as affected by muscular work, they did not include at least a 

 few experiments with an oxygen consumption of from 1,500 to 3,000 

 c. c. per minute, as it was especially in regard to these periods of severe 

 work that Benedict and Murschhauser made their recommendations 

 as to method of study. Indeed, the results given in this present re- 

 port (see table 56, p. 221) show high respiratory quotients, which, in 

 the absence of demonstrated technical or physiological error, lead only 

 to the conclusion that there is a specific, selective carbohydrate com- 

 bustion with this intensity of performance. 



TOTAL HEAT-OUTPUT DURING GRADE WALKING. 



The total heat expended per minute during grade walking is given 

 in tables 13 to 16, and also in column j, tables 52 to 55, and indicates 

 the range of requirements for men of different weights at different 

 grades and speeds. As the amount of heat produced is conditioned 

 upon the work accomplished per minute, no direct comparison can be 

 made except on the basis of kilogrammeters of work performed. These 

 values, computed from the body-weight and grade-lift, are given in 

 column / of tables 52 to 55. 



The range in the total amounts of heat developed during grade walking 

 is limited in the case of the two subjects, T. H. H. and H. R. R., as they 

 dropped out of the study before any severe amount of work was per- 

 formed. The range for W. K. is from 3.72 to 10.57 calories, with 

 approximately 125 to 900 kg. m. of work, and for E. D. B. from 2.59 to 

 15.65 calories for work ranging from 59 to 1,569 kg. m. per minute. 

 This last value is the average of two periods on February 22, when the 

 subject walked up a 40 per cent grade at a rate of 65.2 meters per 

 minute (2.50 miles an hour). The first period was of 10 minutes dura- 

 tion, with 13 minutes of preliminary walking. At the close of the 

 period, the subject complained of pains in his chest and was doubtful 

 of his ability to perform a second period of similar activity. The dura- 

 tion of the last period was reduced to 6 minutes after a preliminary 

 walk of 5 minutes, as the subject showed signs of exhaustion. 



If the values for the total heat-output per minute are plotted on the basis 

 of kilogrammeters of work, as is done in figures 21 and 22, it is seen that 

 the total heat-output is a linear function of the work performed for each 



'Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915, p. 30. 



