PHYSIOLOGICAL EFFECTS OF GRADE WALKING. 273 



In curve D a graphic record is given of the body-temperature found 

 in the experiment of February 18, with E. D. B. walking at an average 

 rate of 50 meters per minute on a 40 per cent grade. Here, also, the 

 walking was preceded by a period of standing, with practically the same 

 body-temperature at the beginning as in curve C. In contrast to 

 February 17, the rise in the first 19 minutes of walking was but 0.66 C., 

 or 0.03 C. per minute. The slope of the curve for the grade walking 

 is practically constant up to 38.50 C., and thereafter the rate of in- 

 crease diminishes. Although the grade was 5 per cent greater on 

 February 18 than it was on February 17, a decrease in speed of 12 me- 

 ters per minute resulted in a smaller amount of work on this day 

 (1,188 kg. m. as compared with 1,306 kg. m. on February 17), which 

 was sufficient to retard the rise in the body- temperature. In this 

 experiment there was continuous walking from 9 h 25 m to 10 h 35 m a. m. 

 (1 hour and 10 minutes), with a total increase in temperature of 1.96 C. 

 and a maximum temperature of 39. 10 C. The subject was much out of 

 breath when he stopped walking and was sweating freely. As stated 

 earlier, the electric fan was not used for cooling during the experi- 

 ments with E. D. B. (See p. 37.) 



Curve B hi figure 35, which gives records for the experiment on Feb- 

 ruary 22, when the grade was 40 per cent and the speed 65 meters per 

 minute, represents the temperature on the day when E. D. B. did his 

 maximum amount of work of 1,569 kg. m. per minute with an oxygen 

 consumption of 3,132 c. c. per minute, and a total heat-output per 

 minute of 15.65 calories. Although the maximum body-temperature 

 was not so great as that shown in curve D, when the walking was con- 

 tinuous for 1 hour and 10 minutes, yet the increment during walking 

 is shown by curve B to have been 1.62 C. in 23 minutes. This was an 

 increase at the rate of 0.07 C. per minute. The rate of increase is 

 thus larger than that shown in curves C and D when the temperature 

 rose 0.04 and 0.03 C. per minute, respectively, and the work performed 

 was less. It may reasonably be said, therefore, that for amounts of 

 work over 1,000 kg. m. per minute, the body-temperature may increase 

 from 0.03 to 0.07 C. per minute for the first 10 to 20 minutes, with a 

 maximum total increase of 1.5 to 2.0 C. 



The curves in figure 36 (February 26 and 15) are included to show 

 more especially the fall in the body-temperature after the walking 

 stopped. In the experiment of February 26 (curve A) the grade was 

 30 per cent and the speed 70 meters per minute. The walking ceased 

 at 10 h 32 m a. m., and in the subsequent period of 2 hours and 3 minutes, 

 during which the man alternately stood and sat, the body-temperature 

 fell 1.58 C. This fall brought the body-temperature below the level 

 in the first standing period of the forenoon. 



In the experiment on February 15 the grade was 35 per cent and the 

 speed was 45 meters per minute. When the walking ceased at ll h 7 m 



