RESEARCHES BY OTHER INVESTIGATORS. 13 



movement of 1 kg. 1 meter in horizontal walking within the range of 

 the maximal economic velocity was not materially affected by loads 

 up to 36 kg. and had derived a formula to express this generalization. 

 Assuming that, according to their findings, the metabolism per hori- 

 zontal kilogrammeter is independent of the speed and that the same 

 relation exists for loads in grade walking as is found in level walk- 

 ing (an assumption which they were not able to confirm), they derived 

 a formula which they believe expresses in approximate form the energy 

 metabolized per kilogrammeter of total weight and meter distance 

 covered between grades of and 35 per cent. They find the optimum 

 condition to be at a grade of 19.8 per cent, with a load of 19 kg., which 

 required an expenditure of 10.1 calories for each kilogrammeter of 

 grade-lift, or an efficiency of 23.1 per cent. It should be mentioned 

 in this connection that Brezina and Reichel do not obtain net effi- 

 ciencies, since they do not deduct the energy for the horizontal com- 

 ponent, but compute the energy from the heat expended over the lying 

 requirements. 



Brezina and Reichel find that for the limited speeds used the rate of 

 walking was without influence upon the energy per kilogrammeter, 

 and also that the total energy per kilogrammeter of grade-lift 

 for grades between 10 and 40 per cent with superimposed loads 

 of from 3 to 56 kg. varied from 10.1 (the optimum value) to 12.4 

 calories, while for lower grades of 2.5 to 7.5 per cent, the measure- 

 ments were as high as 29.3 calories. This large difference was un- 

 doubtedly due to the fact that the work at these low grades was too 

 email a proportion of the total energy metabolized to be accurately 

 determined. Brezina and Reichel give the data somewhat extensive 

 mathematical treatment and derive certain formulae which, in their 

 judgment, make it possible to calculate the increase in energy due to 

 the load and the grade, provided certain limits of speed and load are not 

 overlooked. They likewise include the efficiency as a constant function 

 of the grade. 



The work of Brezina and his associates Kolmer and Reichel is by 

 far the most extensive and painstaking of any of the studies on the 

 physiology of walking, and their conclusions are suggestive. But, 

 as they themselves say, though the study was carried out over a 

 considerable range of speed and grade, the data represent the results 

 of experiments with only one subject and considerably more data are 

 required before then 1 generalizations can be universally accepted. 



In physiological experimenting the use of but one subject has fre- 

 quently been the basis of much adverse criticism of a piece of work. 

 It is true that if but one isolated physiological factor is to be measured, 

 this criticism is a serious one. In a study in which so complicated a 

 process as the energy requirements of walking is concerned, the results 

 of a careful series of experiments like those of Brezina and Kolmer, 



