MECHANICAL EFFICIENCY OF THE HUMAN BODY 
111 
ternal work or load was computed as shown in table 111. The authors point 
out that there was a disturbing factor in that the speed per minute was not 
uniform with all degrees of magnetization of the field, and state that the 
experiments must be looked upon as more or less tentative. 
Table 111. — Effect on mechanical efficiency of increasing external work as reported by 
Benedict and Carpenter. 
Increase in 
magnetization 
from — 
Increase 
of total 
heat. 
Increase 
of heat of 
external 
work. 
Efficiency. 
amp. 
0.7 to 0.8 
0.7 to 0.9 
0.7 to 1.25 
0.8 to 0.9 
0.8 to 1.25 
0.9 to 1.25 
eals. 
19 
89 
237 
70 
218 
148 
eals. 
5 
19 
52 
14 
47 
33 
p.ct. 
26.0 
21.3 
22.0 
20.0 
21.5 
22.3 
As an indication of the great difficulties that may be experienced in com- 
puting the heat efficiency of the bicycle rider from the energy intake and the 
mechanical measurements, we must cite the discussion of R. C. Carpenter,** 
who computed the efficiency of two professional riders in a 6-day bicycle 
race, obtaining the apparent gross efficiencies of over 60 per cent in one case 
and nearly 45 per cent in the other. Computations of the effective muscular 
work in complicated muscular processes must always be of uncertain value. 
One of the great difficulties incidental to computing the amount of 
external muscular work performed by going up and down stairs or walking 
along a horizontal or an inclined plane is strikingly indicated in certain experi- 
ments of Chauveau. 6 This investigator computed that Tissot in his experi- 
ments on the respiratory exchange performed in 70 minutes 29,000 kilo- 
grammeters of positive work and an equal amount of negative work. The 
total amount of work would thus be 58,000 kilogrammeters, or 136 calories, 
approximately 2 calories per minute. And yet Chauveau, in his computation 
of the respiratory quotients, maintains that the metabolism during work was 
but 4 times that of rest. In this laboratory in order to secure an effective 
output of 2 calories per minute on a bicycle ergometer, it was necessary for 
the subject to increase his metabolism over rest more than 10 times. It 
is thus obvious that either Chauveau's estimate of the amount of external 
muscular work performed must be erroneous or the analyses for the gaseous 
exchange are open to severe criticism. The technique of the Chauveau- 
Tissot apparatus has been carefully gone over in this laboratory by Mr. T. M. 
Carpenter, and when carried out according to the specific instructions of 
Chauveau and Tissot, the apparatus and method give admirable results. 
We are thus disinclined to consider the measurements of the gaseous ex- 
change at fault, although the lengths of periods are short and the technique 
of sampling has not been adequately given. It is probable that the estimates 
of the work performed are erroneous. 
Amar, c using a bicycle ergometer in which the rear wheel was supplied 
with a steel ribbon as a brake, the amount of friction on the ribbon being 
J Atwater, Sherman, and Carpenter, U. S. Dept. Agr., Office Expt. Stas. Bui. No. 98, 1901, pp. 64 and 65. 
o Chauveau, Comptes rendus, 1896, 122, p. 1163. Previously cited on p. 80 of this report. 
c Amar, Jules, Le rendement de la machine humaine. Recherches sur le travail, Paris, 1910. 
