140 
MUSCULAR WORK 
with these experiments is this more strikingly brought out than here. Had 
it been possible to have this subject ride at a low rate of speed with this mag- 
netization, an even greater efficiency than here noted might have been found, 
but as the rate of even 70 revolutions per minute was a little lower than he 
liked, since he usually preferred to ride at the rate of 80 or 90 revolutions per 
minute, the experimenting was not extended further in the direction of 
low speeds. 
Table 125. — Efficiency of subject M.A.M. for increased amount of work due 
to increase of 10 revolutions in speed, with current of 1.5 amperes. 
Increase in 
revolutions 
from — 
Effi- 
ciency. 1 
Increase in 
revolutions 
from — 
Effi- 
ciency. 1 
70 to 80 
80 to 90 
90 to 100 
p. ct. 
16.53 
13.47 
11.94 
100 to 110 
110 to 120 
120 to 130 
p. ct. 
10.48 
9.11 
7.82 
1 Efficiency = 
Increase in external work. 
Increase in total heat output. 
It is a striking coincidence that the decrease in the heat given off by the 
ergometer per revolution compensates almost exactly for the decrease in the 
efficiency of the subject, so that the total heat output per revolution of the 
pedal is exactly constant irrespective of speed. 
Thus far in considering the results, the greatest emphasis has been laid 
upon variations in speed per se. The unavoidable variations in the amperage 
and consequently in the actual amount of work performed incidental to 
alterations in the speed evidently might affect the efficiency and this factor 
should also receive special consideration. Had it been possible to conduct 
experiments at 50 revolutions per minute and again at 111 revolutions per 
minute, it will be seen from the calibration curves of ergometer II that we 
would have had exactly the same heat equivalent of effective muscular work, 
and it is perhaps unfortunate that such a series of experiments was not 
attempted. Our experience in having the subject ride at a slow rate was, 
however, discouraging as he found it almost impossible to control his muscles 
so as to rotate the pedals less than once per second. 
In considering these relationships, it is of more than ordinary interest to 
study the influence of speed on the net efficiency when the amount of effective 
muscular work remained constant. For this purpose we have collected such 
experiments as were comparable, and tabulated in table 126 the results ac- 
cording to the heat equivalent of muscular work performed at the different 
speeds. 
The results given in table 126 show that with approximately the same 
heat equivalent of muscular work per minute but with different speeds, the 
net efficiency of the body was very considerably less with the higher speeds. 
For instance, when the heat equivalent of the muscular work per minute was 
approximately 1.95 calories per minute, the average of 18 periods with a speed 
of 90 revolutions showed a net efficiency of 22.6 per cent, while 2 periods 
with an increased speed of 124 revolutions per minute gave a net efficiency 
of 15.7 per cent. Similarly, when the heat equivalent of the muscular work 
was approximately 1.80 calories per minute, the net efficiency with 80 revo- 
