8 METABOLISM DURING WALKING. 



as yet not accompanied by clearly defined experimental proof, that 

 walking in free, open air has a measurably different physiological 

 effect from that of walking on a treadmill in a more or less closed 

 laboratory. In any event, this effect must be relatively small in 

 degree as compared to the effect of grade walking. Consequently, all 

 contributions to technique or to the physiology of horizontal walking 

 that will make the establishment of the normal base-line more definite 

 are to be welcomed, for the problem of the difference in effect of walking 

 in the open air as compared to walking on a treadmill in a well-venti- 

 lated room can only be solved by the use of impeccable technique. 



GRADE WALKING. 



The majority of the studies which involve grade walking have been 

 made in connection with studies of the effects of high altitudes upon 

 the physiological actions of the human organism. The conditions of 

 high altitudes, mountain paths, and, in many cases, a previous diet, 

 must be taken into consideration in examining the results. In prepara- 

 tion for these mountain expeditions, nearly all the researches included 

 a series of treadmill experiments which alone are really comparable 

 with our results. Most of the results in these experiments were 

 obtained by the Zuntz method. With this method the subject 

 breathes through suitable valves, the volume of air is measured, and 

 its composition determined by analysis of carefully drawn samples. 

 From the known heat value of a cubic centimeter of oxygen or carbon 

 dioxide for the respiratory quotient found, the energy expended per 

 unit of time is then calculated. 



The basis for comparison was the carbon-dioxide production, the 

 oxygen consumption, or the heat expended per kilogrammeter of work 

 done by the subject in lifting his body- weight, plus any loads he carried 

 in the form of equipment, such as gas-meter, etc., to the elevation 

 attained by the grade, or briefly, the work of the "grade-lift." The 

 question of the proper base-line has been variously treated. The 

 resting or maintenance metabolism in either the lying or the standing 

 position has been universally deducted from the total gaseous exchange 

 measured, but the allowance for the so-called "horizontal component" 

 has been variously regarded. It is more generally estimated as 

 equivalent to an equal linear distance found from horizontal-walking 

 experiments. In other cases, no allowance has been made for this 

 factor, but the energy expended per meter of distance walked and 

 kilogrammeter of lift is reported. 



In 1891, Katzenstein 1 made some measurements of the gaseous 

 metabolism during grade walking in the laboratory of Zuntz in Barlin, 

 employing a treadmill and the Zuntz method of measuring the gaseous 



Katzenstein, Arch. f. d. ges. Physiol., 1891, 49, p. 330. 



