308 METABOLISM DURING WALKING. 



period, representing a time-interval of 2 hours after walking ceased, 

 that the temperature may be said to approximate anything like the 

 original values. 



The after-effects of exercise on the gaseous exchange have recently 

 been studied by Campbell, Douglas, and Hobson, 1 and by Krogh and 

 Lindhard, 2 who followed the changes through brief intervals. These 

 authors find, in harmony with Zuntz, with Benedict and Cathcart, and 

 with others, that the respiratory quotient increases when the work 

 stops; after a brief period it falls to a value somewhat below normal. 



The values here reported for 15-minute periods do not, of course, 

 show the stimulated respiratory quotient for the post-walking periods 

 which, according to Krogh and Lindhard, occurs approximately 

 1| minutes after the end of walking. In the standing periods follow- 

 ing immediately after the cessation of walking (December 21 to 

 February 17), the respiratory quotient is lower than during the walking 

 period, and but little different from the pre-walking quotients. This 

 is probably explained by the fact that the quotients for a period fol- 

 lowing immediately the cessation of walking would be influenced by 

 the high values referred to above as occurring for a short time. It is 

 only when the periods are taken after the temporary high respiratory 

 quotients have passed that the after-effects of walking become evident. 

 All of the post- walking periods of February 26 to 29 on which there 

 was an interval of rest following the walking indicate a lowered respi- 

 ratory quotient in relation to both the pre-walking and the walking 

 respiratory quotients. On two of these days the subject had walked 

 somewhat over an hour and on the last day about half that time. 



Campbell, Douglas, and Hobson conclude that the possible presence 

 of lactic acid in the muscles is alone not sufficient to explain the be- 

 havior of the respiratory quotient following the cessation of work and 

 are inclined to believe with Zuntz and with Benedict and Cathcart 

 that the probable explanation is that during the period of walking the 

 glycogen reserve in the body is depleted and that during the subse- 

 quent periods proportionally less carbohydrate than fat is consumed 

 in the body metabolism. 



A rough estimate of the amounts of glycogen consumed during 1 

 hour of walking on the basis of an oxygen consumption of 2,500 c. c. 

 per minute and a respiratory quotient of 0.90 is as follows: The total 

 energy produced in 1 hour would be approximately 750 calories; if 

 60 per cent of this energy were derived from carbohydrate to produce 

 the respiratory quotient of 0.90, as assumed by Magnus-Levy, 3 and 

 4.23 calories be assumed as the heat-production from 1 gram of gly- 

 cogen, the total amount of glycogen consumed in 1 hour of walking 



Campbell, Douglas, and Hobson, Phil. Trans., London, 1920, Ser. B, 210, p. 1. 

 2 Krogh and Lindhard, Journ. Physiol., 1920, 53, p. 431. 



3 Magnus-Levy, in von Noorden's Handbuch der Pathologie des Stoffwechsels, Berlin, 2d ed., 

 1906, 1, p. 207. 



