MECHANICAL EFFICIENCY OF THE HUMAN BODY 
145 
later experiments were planned more particularly for studying this point and 
are hence much more complete and more numerous than the earlier experi- 
ments, we find it impossible to explain in any way the lower values found by 
Benedict and Carpenter with the ergometer I used by us in this research. 
Finally, we should call attention to the fact that while the early observa- 
tions with ergometer I implied a great discrepancy between the efficiency as 
determined by means of this apparatus and that obtained by Zuntz and his 
associates in their mountain-climbing and treadmill experiments, the later 
research gives results that agree with the best figures obtained by the Zuntz 
method, namely, 33 per cent. 
Relationship between Efficiency and the Character of the Diet. 
Several sets of experiments were planned to test the effect upon the 
efficiency of the character of the diet. While the evidence obtained is by 
no means conclusive, such results as are suitable for comparison have been 
gathered together in table 129 for examination and discussion. 
Table 129. — Heat output in work experiments without food following diets carbohydrate^rich 
and carbohydrate-poor. Subject M. A . M . 
Carbohydrate-rich diet. Carbohydrate-poor diet. 
Date. 
No. of 
diet days 
preceding 
experi- 
ment. 
Heat equiv- 
alent of ex- 
ternal work 
per minute. 
Heat output \ 
per calorie ' 
of external 1 
work per 
minute 
(calculated). 
Date. 
No. of 
diet days 
preceding 
experi- 
ment. 
\ Heat output 
Heat equiv- t per calorie 
alent of ex- 1 of external 
ternal work j work per 
per minute, i minute 
| (calculated). 
1912. 
Jan. 24 , 
Jan. 25 
Jan. 26 
Feb. 14 
Feb. 15 
Feb. 16 
1 
2 
3 
1 
2 
3 
cats. 
2.05 
2.18 
2.11 
2.11 
2.08 
2.08 
cals. 
5.52 
5.38 
5.81 
5.20 
5.17 
5.12 
1912. 
Feb. 7 
Feb. 8 
Feb. 9 
1 
2 
3 
cols. 
2.07 
2.12 
2.03 
cals. 
5.30 
5.40 
5.23 
5.31 
Jan. 17.... 
Jan. 18.... 
Jan. 19.... 
1 
2 
3 
1.57 
1.59 
1.56 
6.52 
6.62 
6.89 
5.37 
Jan. 8>.... 
Jan. 9i 
Jan. 15 l . . . . 
1.50 
1.48 
1.64 
6.51 
6.31 
7.17 
6.66 
6.68 
1 The experiments made on Jan. 8, 9, and 15 followed days with ordinary or unrestricted diet. The aver- 
age respiratory quotients for these days were respectively 0.88, 0.88, and 0.90 (lying before work). 
As Zuntz has pointed out, if Chauveau's theory be correct, when fat is 
burned 30 per cent more energy per unit of work should be liberated than when 
carbohydrate or glycogen is burned, since Chauveau contends that fat must 
first be converted into glycogen, during which process heat is liberated which 
is not available for muscular activity. It would appear, therefore, that if 
there were so great a difference as 30 per cent between values obtained with 
diets which were carbohydrate-rich and diets which were carbohydrate-poor, 
such difference should be observed in these experiments. As already pointed 
out, the dietetic control was unfortunately not all that could be desired in 
the experiments in which this question was studied. The respiratory quo- 
tients show, however, that in general on the days when a carbohydrate-poor 
diet was being ingested, the average quotient the next morning was somewhat 
lower than with a carbohydrate-rich diet. (See table 94.) 
