236 



METABOLISM DURING WALKING. 



basal requirements form a part of these total values, the cost per kilo- 

 grammeter of work is naturally larger when the work is small and de- 

 creases with increasing work. This is clearly seen from the figures col- 

 lected in table 62, in which the data for E. D. B. for increasing amounts 

 of work are given in a more extended form than in table 61. The total 

 heat cost per kilogrammeter is here shown to decrease rapidly at first, 

 with increasing amounts of work, but soon reaches a limit; above 1,000 

 kg. m. the total cost is approximately constant at 10 gram-calories per 

 kilogrammeter of work of grade-lift. The fact that the total heat- 

 output per kilogrammeter of work accomplished is less for a steep 

 grade and slower speed than for a low grade and a high speed, as seen 

 from the relative positions of the curves in figure 21 and with most of 

 the curves in figure 22, and that the heat-output per kilogrammeter is 

 lowest when the largest amount of work is done in unit time, as seen 

 in table 62, may explain why many trained walkers prefer a short 

 and steep ascent to a more circuitous and gradual one. 



Curves for the average total heat-output of W. K. and E. D. B. with 

 different amounts of work, due to varying grades and speeds, are in- 

 cluded in figures 23 and 24. These curves are based upon the data in 

 table 56, in which the values are grouped according to grade and rate of 

 walking. The curve for W. K. indicates a slight tendency to deviate 

 from a straight line at the lowest point, but that for E. D. B. is linear 

 throughout its entire length of 1,600 kg. m. If we estimate the basal 



o, 



FIG. 23. Total oxygen consumption and heat-produc- 

 tion of W. K., referred to kilogrammeters of work 

 performed in grade walking. (Values per minute 

 from table 56.) 



