MECHANICAL EFFICIENCY OF THE HUMAN BODY 
125 
The values for the net efficiency given in table 116 were computed by 
establishing the relationship between the heat equivalent of external muscular 
work and the increase in the metabolism during the work-period over that 
required for body maintenance when the subject lay quietly upon a couch. 
As will be seen later, the term "net efficiency" is not particularly felicitous 
in this connection as the value to be deducted from the total heat output 
may vary greatly with the conditions, but in computing the net efficiencies 
shown in table 116, the metabolism when the subject lay quietly upon a 
couch was selected as the base so that the results could be easily compared 
with those of earlier experiments. On inspection of the table it is seen from 
the data for the heat equivalent of external muscular work that the net effi- 
ciency also increased with the load. 
While the great disparity in the number of experiments made with 
these different individuals prevents a strict comparison, such a comparison 
is not without interest, and accordingly in table 117 the highest efficiencies, 
both gross and net, are given for the six subjects. The difference between the 
gross and net maximum efficiencies with these individuals is approximately 
3 per cent, the net efficiency being usually about 3 per cent higher than the 
gross efficiency. If we compare these maximum values it will be seen that 
those for the professional subject M. A. M. indicate a distinct advantage over 
those found with the untrained individuals. On the other hand, the advan- 
tage is not so great as would be expected when it is considered that these 
subjects were absolutely without training and, indeed, in some instances 
were unfamiliar with bicycle riding. Furthermore, since the value found for 
M. A. M. is a selected value out of several hundred obtained with this man, 
and those secured with the other subjects were few in number, it is obvious 
that such a comparison is not justifiable; this table is accordingly not par- 
ticularly adapted for studying the difference in efficiency between trained 
and untrained men. 
Table 117. — Maximum gross and net efficiencies of subjects in respiration experiments 
with the bicycle ergometer. 
Subject. 
Gross. 
Net. 
Subject. 
Gross. 
Net. 
E. P. C. 
J. J. C. 
H. L. H. 
p. ct. 
19.9 
17.8 
18.6 
;•• ct. 
23.1 
20.4 
21.6 
J. E. F. 
K. H. A. 
If. A. M. 
p. ct. 
19.8 
18.2 
21.2 
p. ct. 
22.7 
20.8 
25.2 
While in general there is a tendency toward an increase in both gross 
and net efficiency with the increased load, nevertheless on inspection of the 
results, especially those for the subject M. A. M., we find certain inequalities 
that at first sight are difficult to explain. Making due allowance for abnormal 
figures which may be obtained in the individual periods, we find that there is 
at times a tendency towards a distinct faffing off in the gross and net effi- 
ciency particularly when higher loads are used. That there may be variations 
in the efficiency even with the same amount of external muscular work is 
strikingly shown by a comparison of the experiment on April 8 with that 
of February 29. (See table 116.) In the first three periods of the experiment 
of April 8, the effective work averaged 1.35 calories per minute, the rate of 
