310 METABOLISM DURING WALKING. 



minute, and from 12 to 10 gram-calories per kilogrammeter when the 

 work was between 1,000 and 1,500 kg. m. per minute. (See also 

 table 62.) 



The average increment in the heat-output due to grade walking 

 was approximately 7.5 gram-calories per kilogrammeter of work per- 

 formed. From the results of this study it may be said that the net 

 efficiency with which a person can walk up-grade is not far from 30 per 

 cent when the work is under 500 kg. m. per minute, but when the work 

 amounts to more than 500 kg. m. per minute, the efficiency decreases 

 as the work increases. (See table 69.) 



The measurements of the pulmonary ventilation during grade walk- 

 ing show that the increase in this physiological factor for each increase 

 of 100 kg. m. of work was from 3 to 5 liters, while the total percentage 

 increase with excessive work was as much as 850 per cent above the 

 standing requirement. (See tables 76 and 77.) This enormous in- 

 crease indicates the wide margin which must be provided in designing 

 gas-masks to be worn during excessive muscular work. 



During grade walking, the respiration-rate for the subject E. D. B. 

 showed constant increase over the standing value of 1.2 respirations 

 for each 100 kg. m. increase in the work when over 500 kg. m. of work 

 was done. With the subject W. K. the increase over the standing res- 

 piration-rate was more nearly 2 respirations per 100 kg. m. (See tables 

 74 and 75.) The percentage increase over the standing rate was from 

 8 to 10 per cent for W. K., while for E. D. B. the increase was as high 

 as 40 per cent for the first 100 kg. m., but fell rapidly with increase in 

 the amount of work and became constant at approximately 8 per cent. 



In horizontal walking the pulse-rate frequently was less than that 

 with the subject standing, even with an increase in the metabolism of 

 100 to 200 per cent. During grade walking, the pulse-rate showed a 

 practically uniform increase with the increase in the amount of work 

 performed. The increment in the pulse-rate over the rate found for the 

 standing position rose rapidly with the increase in the work performed ; 

 though the percentage increase per 100 kg. m. of work remained fairly 

 constant, considerable differences were shown between individuals. 

 (See tables 78 and 79.) 



The body- temperature showed increases as high as 2 C., indicat- 

 ing for a body-weight of 60 kilograms a storage of heat in the body 

 of approximately 100 calories. 



From the measurements taken at the time of transition from stand- 

 ing to grade walking, it is believed that in most cases the body adjusts 

 itself to the new demands as to pulse, respiration -rate, pulmonary 

 ventilation, and oxygen-supply by the end of the third minute, and 

 by far the larger part of the adjustment has occurred within 30 sec- 

 onds. The recovery after exercise, however, is not so prompt, and 

 the after-effects of the walking persist for a much longer time before 

 initial conditions are reestablished. 



