MECHANICAL EFFICIENCY OF THE HUMAN BODY 135 
increase in load without change in the speed. Since under these conditions 
the increase in the metabolism can be readily compared with the increase 
in effective muscular work, it would appear as though this was a most advan- 
tageous method of comparison. 
In other experiments, when the subject was riding with a current through 
the armature of 0.95, 1.1, and 1.25 amperes, the rate of speed was such as to 
make the results comparable with similar experiments carried out with a 
current of 0.5 ampere. Hence comparisons can be made and deductions 
drawn from the differences in the metabolism and in the muscular work per- 
formed incidental to the change from a low to a higher resistance. This com- 
parison has been made in table 122, the values with the 0.5 current being 
used as a base-line; the method of computation is exactly that used for the 
values given in table 121. As would be expected, the experiments which can 
be used for this comparison are relatively few but fortunately they are all 
with the same individual, i. e., the professional subject, M. A. M. Here 
again the results show that the average efficiency on this basis of computation 
is not far from 27 per cent and with the exception of the single experiment 
on February 23, the highest efficiencies are found with the lowest rates of 
speed. 
Efficiency in Work Experiments Based xtpon Values Obtained with a 
Current of 0.95 Ampere. 
Finally, although the data are insufficient for an exhaustive discussion, 
we have computed the efficiency using the values found with a current of 
0.95 ampere as the base-line and determining the increase when the load was 
changed to 1.5 amperes without changing the speed. The results have been 
collected in table 123. Discarding the two high values of February 23 and 
February 29 which probably are abnormal, the results as a whole show a gen- 
eral average of 32 to 33 per cent efficiency, somewhat higher than that found 
with the comparison between 0.5 ampere and 1.5 amperes. It is quite possible \s 
that the light load of 0.5 ampere was hardly sufficient completely to eliminate 
extraneous muscular motions on the part of this subject, since there may have 
been at times an irregularity in the rate of speed or even back pedaling; 
while the values obtained with the 0.95 load indicate that this load required 
more constant work with much less liability of variations in speed. It 
would appear, therefore, as if with this particular subject the highest effi- 
ciency is obtained by using first a moderately severe load and then changing 
to a very severe load. 
From observation of the subject while he was riding, particularly of 
the traction on the sprocket-chain, it appeared that with a resistance of 0.95 
ampere, the extraneous muscular motions incidental to riding were the same 
as with the higher resistance, so that unquestionably the only two variable 
factors were the speed and the intensity of magnetization. For purposes 
of comparison, therefore, the results obtained with a moderate amount of 
work give the most logical base-line, since variability in the extraneous mus- 
cular motions is eliminated. Consequently, with this type of ergometer, 
when the speed is the same and the degree of magnetization is varied, the 
difference in work with this base-line may be consistently used for computing 
the efficiency. When it is considered that the values in table 123 were de- 
