534 VITALITY AND EFFICIENCY WITH RESTRICTED DIET. 



lism. The treadmill experiments may be looked upon, therefore, from 

 two standpoints, first, as to the capacity of the organism to carry out a 

 simple physical operation, such as that of walking a given distance, and 

 second, as to the efficiency with which the operation may be done. 

 Knowing from the earlier researches of Durig and his associates that 

 when weight is added in the form of a load on the back, the energy 

 required for the transportation of this material is, up to a certain 

 limit, essentially constant per kilogram of body-weight, we could 

 assume a priori that when these men had lost a certain amount of weight 

 they would be able to walk a given distance with a lower metabolism. 

 It should be borne in mind, however, that the experiments of Durig 

 deal with a basal metabolism of a constant intensity and with an organ- 

 ism living at a normal nutritional level. Although it has been shown in 

 the foregoing sections that the basal metaboHsm was very greatly 

 lowered as a result of the restricted diet, it is not logical to assume, 

 without supporting experimental evidence, that the walking would be 

 accomplished necessarily with essentially the same degree or a less 

 expenditure of energy. 



In addition to considering the capacity of the organism to transport 

 itself a given distance, one may very properly consider whether the 

 energy required to transport 1 kg. of body-weight 1 meter in a hori- 

 zontal direction has been materially afTected by the change in diet. 

 With a relatively large number of individuals, at least, the average 

 figures have shown approximately uniform constancy for this factor. 

 This is more of an abstract physiological phase of the problem and of 

 somewhat less practical importance. In the following analysis of our 

 walking experiments, therefore, we will first consider the capacity of 

 the organism as a whole to transport itself or to walk a given distance, 

 in the belief that walking makes up a not inconsiderable amount of the 

 activity of each individual during the day, and likewise, as has been 

 pointed out earlier, walking is one of the most practiced and commonest 

 muscular performances of mankind. 



The technique described in an earlier section, employing the tread- 

 mill and the closed chamber with gas analyses for both carbon-dioxide 

 increment and oxygen deficit, was utilized to determine the total heat 

 production during the process of walking. It has been the custom of 

 investigators, however, to recognize that a certain proportion of this 

 heat is required for the ordinary maintenance activity. In the calcu- 

 lation of the heat required for walking, this maintenance energy is 

 usually deducted from the total heat during the walking period. The 

 time available for these experiments was not sufficient for us to deter- 

 mine both the total heat production of walking and the heat of main- 

 tenance in the treadmill chamber. Use was therefore made of experi- 

 ments with the portable apparatus, in which the subject was in the 

 standing position, it being the consensus of opinion of physiologists 



