230 



METABOLISM DURING WALKING. 



the total energy expended above the standing requirement is charged 

 to the work accomplished, a large amount of work is more economically 

 performed than a small amount, since that portion of the energy 

 requirement which might be regarded as a general or fixed charge^is 

 distributed over a larger return in the work accomplished. 



RESPIRATORY QUOTIENT DURING GRADE WALKING. 



The effect upon the respiratory quotient of varying amounts of 

 work in grade walking may be seen from the data in tables 52 to 55 

 and in table 56. The obvious effect of work is to increase both the 

 carbon dioxide produced and the oxygen consumed, with an accom- 

 panying increase in the pulmonary ventilation. If the increased ven- 

 tilation of the lungs causes a sudden sweeping out of the preformed 

 carbon dioxide in the blood before equilibrium with the oxygen demands 

 can be met, the respiratory quotient is increased, or if the character 

 of the metabolism is changed whereby the energy will be supplied 

 from the carbohydrate store of the body rather than from the fat, 

 the result will be an increase in the respiratory quotient. 



FIG. 20. Respiratory quotients of W. K. and E. D. B. referred to 

 kilogrammeters of work performed in grade walking. (Val- 

 ues per minute from table 56.) 



The respiratory quotient of the normal subject in the post-absorp- 

 tive condition is not far from 0.82 to 0.85, and from our measurements 

 of the transition requirements (see p. 296), it would appear that the 

 oxygen consumption and ventilation reached constancy within 2for 

 3 minutes after the change from rest to work. As the subject walked 

 5 to 10 or more minutes previous to each period, it is therefore believed 

 that before the period began the carbon dioxide and oxygen had 

 become constant at the rate demanded by the work, and that the 

 respiratory quotient would be of the average normal value unless an 

 alteration in the character of the metabolism bad taken place. 



It is seen in table 56 (p. 221) that the average respiratory quotient 

 for the different subjects was not different from the normal standing 

 average for the lower grades and speeds, 0.87 being the highest average 

 value found for any of the subjects below a 10 per cent grade at 60 to 



