tially the same rates of revolution were employed, a comparison being made of the work done with a current of 1.5 amperes with that done with a current of 0.5 ampere. By deducting from the total energy output when the subject rode at 1.5 amperes the heat given off when he rode at 0.5 ampere and comparing the difference with the difference in the external muscular work performed in the two cases, it is possible to compute an efficiency on a basis that is open to less objection than any other base-line that we have thus far proposed.

TABLE 122.-Efficiency in respiration experiments with bicycle ergometer II with currents of 0.95, 1.1, and 1.25 amperes. Subject, M.Ă. M.

[Basal values obtained in experiments with current of 0.5 ampere.]

8 Average of results obtained on Feb. 28 and Mar. 4, the oxygen being 1,170 and 1,061 c.c., respectively. 4 Result obtained on Feb. 28.

6 Average of results obtained on Mar. 12 and 13, the oxygen being 807 and 837 c.c., respectively.

6 Average of results obtained on Mar. 12, 14, and 18, the oxygen being 797, 787, 823 c.c., respectively. 7 Average of two results obtained on Mar. 14.

Disregarding individual periods with exceptionally high or low values, it can be seen that with the professional subject the average efficiency on this basis is not far from 30 per cent. Essentially the same value is found for the untrained subject E. P. C., while the other untrained subjects J. E. F., K. H. A., and J. J. C. show somewhat lower percentages. The values for the subject M. A. M. are for the most part very regular, ranging in the 18 experiments from 26.8 per cent to 33.2 per cent, with practically all of the values between 29.7 and 31.0 per cent.

When the speed is taken into consideration in all the comparisons, however, we have for the first time the opportunity to study the effect of an

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 advantageous 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 performed incidental to the change from a low to a higher resistance. This comparison 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 UPON 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 general 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 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 efficiency 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 muscular 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

rived from individual periods and they are consequently liable to all the possible errors in individual experimentation, the agreement is on the whole remarkably satisfactory.

TABLE 123.-Efficiency in respiration experiments with bicycle ergometer with a current of 1.5 amperes. Subject, M. A. M.

[Basal values obtained in experiments with current of 0.95 ampere.]

GENERAL CONSIDERATION OF THE EXPERIMENTAL DATA OBTAINED WITH THE PROFESSIONAL SUBJECT M. A. M.

With the professional subject M. A. M., such an extensive series of experiments was obtained at the magnetization of 1.5 amperes and with all possible speeds that it seemed practicable to establish a definite mathematical relationship between the muscular work performed and the total heat output. As frequently stated in the discussion of these tables, individual periods or experiments may give abnormal results, and the reader has been cautioned not to put undue confidence in these. We believe, however, that the best method of studying the research as a whole is to give all of the data careful scrutiny and, if possible, secure a series of curves from which the efficiency and the total heat output at any speed may be obtained. For this purpose we have used the results secured with M. A. M. at speeds ranging from 70 to 128 revolutions to plot a curve showing the probable value for the oxygen consumption at the different rates of speed. With a magnetization of 1.5 amperes, average values were secured at 70, 80, 90, 95, 102, 110, 113, 117, and 128 revolutions per minute respectively. The points for 70, 90, 95, 102, 110, and 113 revolutions were obtained from an average of five or more periods at or about these speeds; for 80 revolutions the point was secured from the results of 3 periods; for 117 revolutions from 2 periods; and for 128 revolutions from only 1 period. In a similar manner the results obtained with magnetizations of 1.25, 1.1, 0.95, and 0.5 amperes were used to plot curves for the oxygen consumption per minute for different speeds. These curves are all given in fig. 4.

It is seen that the form taken by the most probable curve is, in all degrees of magnetization, a straight line and consequently there is a regular agreement between the oxygen intake per minute and the rate of revolution,

each revolution corresponding to a definite oxygen intake, i.e., 23.1 c.c. with a magnetization of 1.5 am

peres.

3,100

however, another form of curve

Leaving out of consideration

2,100

2,000

1,700

1,600

1,400

the slight inequalities in the in- 2,300
dividual points found with the 2,200
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 1,900
respiratory quotient found in the
experiments. A curve was then 1,800
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 1,500
curve does not differ materially
from that shown in fig. 4 for the
oxygen consumption, both being 1,300
straight lines. It is seen from the
curve that the total heat given off 1,200
from the body per revolution of the
pedals was constant at all speeds.
To accentuate the fact that the 1,000
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

1,100

900

800

60 70 80

FIG. 4.-Curves showing oxygen consumption per minute with the subject riding at different speeds and with varying loads.

The revolutions per minute are given at the bottom of the figure and the oxygen consumption in cubic centimeters per minute at the left.

a See fig. 1, p. 27.

the curve for the total heat output per minute with varying revolutions shows 7.61 calories at 70 revolutions per minute, and 15.04 calories at

2.30

2.20

2.00

1.90

1.70

As the result of the winter's experimentation on this subject with a resistance of 1.5 amperes, these two curves may be taken 2.10 as representing his muscular relationship to ergometer II. With these curves, therefore, it is perfectly possible to compute the total heat output and the energy 1.80 output of the effective muscular work and from these values to compute the efficiency of the 1.60 subject for the various rates of revolution. Such a computation of the efficiency would naturally be much more satisfactory than if it were based upon the results for the individual periods shown in the tables, since the inequalities which occasionally appear and which affect the general trend of the tabular matter, disappear when using the curves; it therefore seems advisable to enter somewhat more

1.50

1.40

60 70 80 90 100 110 120 130 140 FIG. 5.-Curves showing the total heat output per minute and corresponding external muscular work per minute, expressed in calories, for subject riding with constant load-1.5 amperes at varying speeds.

The revolutions per minute are given at the bottom of the figure, the heat output per minute at the left, and the effective work performed per minute, expressed in calories, at the right.

fully into the discussion of the efficiency of the subject, using the data projected in these curves as the basis.

RELATIONSHIPS BETWEEN SPEED AND EFFICIENCY.

Under these circumstances we may now for the first time intelligently consider the relationship between speed and the gross efficiency. It was noted in the discussion of table 116 that while the efficiency increased in general