INTRODUCTION. 



METHODS OF DETERMINING THE ENERGY TRANSFORMATIONS 



DURING WALKING. 



It is necessary, first of all, to study the energj^ transformations which 

 are peculiarly incidental to walking. Thus, in the simplest case, if 

 the person could walk directly in a vertical direction, a definite amount 

 of external muscular work would be performed which would be repre- 

 sented by the product of the weight of the body and the height walked. 

 In walking in a horizontal direction, theoretically no external work is 

 performed and there is no change in the potential energy of the body. 

 We are thus unable to measure the energy output by the kilogram- 

 meter, the unit most commonly used, or by any of the other ordinary 

 work units. Consequently we have very little information regarding 

 the energy output. 



It is true that we must not disregard the extremely illuminating 

 researches of earlier workers, who have attempted to establish a con- 

 stant, although with wide variations, which would show approximately 

 the amount of energy required to move 1 kilogram 1 meter in a hori- 

 zontal direction. These researches will be referred to in a subsequent 

 section. It is important for us to note, however, that aside from such 

 methods of calculation as are based upon the constant established by 

 the earlier physiologists, we have no means of calculating the energy 

 output required in walking. 



A possible method of measurement would be to determine the energy 

 output directly by having the subject walk inside of a calorimeter. 

 This has been attempted, although in an imperfect manner, by certain 

 French investigators, including Him 1 and Chauveau, 2 who used the 

 so-called " emission calorimeter" with a tread wheel. In these studies, 

 however, a large proportion of the work was done in lifting the body, 

 and hence the amount of forward progression, which is of special interest 

 to us, is complicated by the very much greater work involved in the 

 elevation of the body. 



Finally, it is possible, owing to the valuable computations and 

 methods of research established by Zuntz, to study the respiratory 

 exchange, namely, the carbon-dioxide output and the oxygen intake, 

 and thus compute indirectly the total calorific output. This last 

 method has been adopted by all physiologists as the most suitable for 

 the purpose. Practically all previous research has therefore been 

 based upon the general principle of determining the total respiratory 

 exchange both while the subject is walking and during rest when lying, 

 sitting, or standing, and noting the increment in the carbon-dioxide 

 output and oxygen intake due to walking. 



From the heat of combustion and analysis of pure nutrients, such 

 as carbohydrate and fat, it has been computed that for each liter of 



, Recherches sur 1'equivalent mecanique de la chaleur, Paris, 1858. 

 2 Chaveau, Compt. rend., 1899, 129, p. 249. 



