262 METABOLISM DURING WALKING. 



creases over the standing requirements as well as the increase over the 

 standing requirements per 100 kg. m. of work performed. These figures 

 show an increment over the standing requirement of 777 per cent for 

 W. K. for 900 kg. m. and 857 per cent for E. D. B. for 1,600 kg. m. of 

 work. For a unit amount of work of 100 kg. m., however, there is a 

 gradual decrease up to 600 kg. m. for W. K. and to 800 kg. m. for E. 

 D. B. Beyond these points the ventilation per 100 kg. m. increased 

 in each case, reaching 5.6 liters for W. K. as compared with 3.5 liters 

 for E. D. B. at 900 kg. m. 



PULSE-RATE DURING GRADE WALKING. 



The pulse-rates for a definite grade and speed of walking are influenced 



in these experiments by several factors, but chiefly by (1) the daily rate 



for the standing position, which, as seen from tables 3 to 7, shows 



variation from day to day; and (2) the variation in the speed at which 



the subject walked, due to our inability to control exactly the speed of 



the treadmill. Furthermore, it is noticeable in the data in tables 13 to 



16 that almost without exception the average pulse-rate increased with 



each succeeding period. As has been stated, the pulse-rates for the 



individual periods represent an average, in most cases, of 3 one-minute 



records. This increase from period to period may, in some cases, be 



due to the gradual alteration in the speed at which the subject walked; 



but since there are numerous instances when the pulse-rate increased 



though the speed decreased, the increment in pulse-rate is more likely 



due to fatigue with the continuation of the work. The increase from 



period to period is seen to have a variation of from 2 to 3 beats per 



minute to as high as 15 beats, with a total accumulated increase in the 



pulse-rate during a forenoon in a few instances of as much as 30 beats 



a minute while the same work is being performed. This rise in the 



pulse-rate, due to the cumulative effect of the exercise, makes the values 



given as the average for the day misleading, for an average made up of 5 



or 6 continuous walking periods would be much higher than when but 



half that number of walking periods are included in the experiment. 



Furthermore, any failure to secure the record of the pulse-rate for a 



period tends to change the average value reported for the day. 



In spite of these difficulties and of the recognized objection to these 

 so-called daily averages, it is believed that the errors that are present 

 are minimized to a considerable extent by the number of the experi- 

 ments and that the general picture is correct. An inspection of the 

 daily averages in tables 13 to 16 shows an approximate pulse-rate for 

 an approximate amount of work performed. This is more apparent in 

 table 56, in which the values are not averages for the individual days, 

 but for the periods falling within 5-meter speed groups with different 

 grades. 



