EXPERIMENTS WITH HORIZONTAL WALKING. 165 



average speeds, as well, indeed, as the average metabolism (see table 

 35), are from the full quota of experiments. The relationship is but 

 little changed, however, if the speed and metabolism averages are 

 based on the same days for which the pulse-records are available. 

 The variations which may occur in the pulse-rates for the same sub- 

 ject are seen by comparing the rates of W. K. for March 17 and 25. 

 The speed of walking on these days was almost identical and the period 

 pulse-rates on each day were uniform, and yet there is a difference 

 between the pulse-rates on the two days of 17 beats per minute. (See 

 table 10, p. 58.) 



With E. D. B. it is seen from table 44 that with the lower speeds of 

 the first three groups the average pulse-rate is 71 and for the next two 

 groups with higher speed the average is 77. Omitting the group for 

 60 to 65 meters per minute, we find that the three speed-groups from 

 65 to 80 meters per minute have an average pulse-rate of 82, and the 

 last two groups an average pulse-rate of 96. Thus, when the subject 

 changed from the lowest average speed of 36.2 meters per minute to an 

 average of 77.5 meters per minute, with an increase in distance walked 

 of 41 meters per minute, the increment in the pulse-rate was but 13 

 beats, whereas a further increase in speed of only 19 meters per minute 

 produced exactly the same increment in the pulse-rate, i. e., 13 beats. 

 This marked change in rate of increase of the pulse at 80 to 85 meters 

 per minute as a result of increase in speed is in keeping with the incre- 

 ment found in the total heat-output for walking above this optimum 

 speed. 



The high pulse-rate for the group 60 to 65 meters per minute is due 

 to the pulse-records for January 31 and February 1, which, it will be 

 recalled, were the first days following the return of E. D. B. from his 

 absence on account of his lameness. In this group is one record on 

 March 30 of a pulse-rate of 82, which is more in conformity with the 

 pulse-rates of contiguous speed-groups, although this value is still 

 somewhat high. With the three subjects, J. H. G., E. L. F., and 

 H. M. S., there is a, fall in the average pulse-rate with the increase in 

 the speed of walking. This is probably due to the fact that the sub- 

 jects were untrained and that the lower speeds were ordinarily used on 

 the first day, when a greater mental stimulus would naturally produce 

 a higher pulse-rate. The fact, therefore, that these three men all 

 showed a lowering of the pulse-rate with increase in speed is not, under 

 the circumstances, so significant. 



. 



COMPARISON OF PULSE-RATE DURING STANDING WITH THAT DtTRING HORIZONTAL WALKING. 



The effect upon the pulse-rate of the activity of level walking, as 

 obtained from a comparison of these group averages with the standing 

 average, may be seen in table 44. With the lower speeds of W. K. and 

 E. D. B. and in all but one instance with the three laboratory men, 



