260 



METABOLISM DURING WALKING. 



TABLE 75. Respiration-rate of E. D. B. with increasing amounts of work in 

 grade-walking experiments without food. (Values per minute.) 1 



upon figure 29. 

 PULMONARY VENTILATION DURING GRADE WALKING. 



The data for the pulmonary ventilation during the grade-walking 

 experiments are also given in detail in tables 13 to 16, pages 69 to 78, 

 from which it is seen that though on some days the ventilation increased 

 from period to period, this increase was not so pronounced and appears 

 to be much more nearly uniform and less influenced by continued exer- 

 cise than was the case with the respiration-rate. Naturally the volume 

 varied with the individual subjects and primarily with the amount of 

 work that was performed. The variations in the rate of increase due 

 to increases in grade and speed are best seen hi the group averages in 

 table 56, from which it is evident that, almost without exception, the 

 average ventilation increased with each increase in speed for the several 

 grades or each increase in grade for a uniform speed. The figures thus 

 give some indication of what may be required by a person when doing a 

 definite amount of muscular work. The significance of these figures 

 in the designing of suitable gas-masks is obvious. In general, it may 

 be said that 17 to 21 liters per minute represents the average rate for a 

 moderate speed of 50 to 60 meters per minute (approximately 2 miles 

 an hour) when the subject is walking on a 10 per cent grade, or when 

 he is doing approximately 335 kg. m. of work. The amount of ventila- 

 tion increased as the grade and speed increased to a maximum of 85 

 liters per minute, as in the case of E. D. B. with 1,569 kg. m. of work. 



As previously stated (see p. 192), the use of the mouthpiece in these 

 grade- walking experiments did not apparently affect the normality of 

 the results obtained for the respiration-rate and the pulmonary venti- 

 lation, notwithstanding the quickened respiration and greater ventila- 

 tion as a consequence of the severe exercise. 



