MECHANICAL EFFICIENCY OF THE HUMAN BODY 
137 
each revolution corresponding to a 
with a magnetization of 1.5 am- 
peres. 
Since the calibration curves 
for this ergometer show that the 
heat per revolution of the pedal 
decreases as the speed increases, 
this must in turn imply that there 
is a distinct alteration in the effi- 
ciency of the body as a machine 
with an increase in speed. For a 
careful consideration of this point, 
however, another form of curve 
projection is necessary. 
Leaving out of consideration 
the slight inequalities in the in- 
dividual points found with the 
curve for the oxygen consumption 
at 1.5 amperes, the total heat pro- 
duction was computed from the 
oxygen consumption, making due 
allowance for the variations in the 
respiratory quotient found in the 
experiments. A curve was then 
plotted from a series of points rep- 
resenting the heat output per 
minute at varying speeds with a 
magnetization of 1.5 amperes. (See 
fig. 5.) As would be expected, this 
curve does not differ materially 
from that shown in fig. 4 for the 
oxygen consumption, both being 
straight lines. It is seen from the 
curve that the total heat given off 
from the body per revolution of the 
pedals was constant at all speeds. 
To accentuate the fact that the 
effective muscular work performed 
is not the same at all speeds we 
also give a curve representing the 
heat output per minute due to the 
effective work performed by ro- 
tating the pedals of the ergometer 
at the varying speeds. This shows 
clearly an increase in the work per 
minute but the increase per revolu- 
tion is less and less as the speed 
increases. For example, in fig. 5 
definite oxygen intake, i.e., 23.1 c.c. 
3,100 
3,000 
2,900 
2,800 
2,700 
2,600 
2,500 
2,400 
2,300 
2,200 
2,100 
2,000 
1,900 
1.800 
1,700 
1,600 
1,500 
1,400 
1,300 
1,200 
1,100 
1,000 
900 
800 
60 70 80 90 100 110 120 130 140 
Fig. 4. — Curves showing oxygen consumption 
per minute with the subject riding at differ- 
ent speeds and with varying loads. 
The revolutions per minute are given at the bottom of 
the figure and the oxygen consumption in cubic cen- 
timeters per minute at the left. 
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f 
7 
1 h 
ft 
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n 
jf 
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Ay 
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X 
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a See fig. 1, p. 27. 
