4 METABOLISM DURING WALKING. 



load of 21 kg. can be carried by the human body as economically as 

 the same amount of live weight. Above either this load or the maximal 

 economic velocity the energy metabolized per horizontal kilogram- 

 meter increases. These authors further state that if a definite weight 

 is to be transported it can be accomplished more economically by 

 increasing the load than by increasing the velocity. As all these ob- 

 servations were made on but one subject (Brezina), the physiologically 

 interesting problem as to the application of these general deductions 

 to persons of widely differing weights remains to be settled. 



Subsequently, Brezina and Reichel 1 made a study of these data of 

 Brezina and Kolmer in an endeavor to express the relations between 

 the increase in metabolism and the increase in load and in velocity. 

 They give the results of their treatment of the data in the form of two 

 generalizations, (a) that for moderate speeds the cost of 1 h. kg. m. 

 is independent of the speed and is smallest for loads of approximately 

 19 kg., and (6) that the energy increase for loads above this maximum 

 weight of 19 kg. is proportional to the square of the load difference. 



(L 19) 2 

 Expressed in terms of calories, the equation is C7=0.5H , in 



J. \J j\J\J\J 



which U equals calories per horizontal kilogrammeter and L equals 

 load in kilograms. Beyond the point of maximal economic velocity, 

 the metabolism increases per horizontal kilogrammeter in geometrical 

 ratio to the arithmetical increase in the speed. 



Benedict and Murschhauser 2 for their two subjects found the energy 

 requirement per horizontal kilogrammeter to be 0.507 and 0.493 

 gram-calorie, respectively, for speeds of approximately 75 meters per 

 minute, that the energy requirements increased with the increase in 

 speed, and that running at 147.5 meters per minute was more economi- 

 cal than walking at the same velocity. A measurement of the energy 

 required for the elevation of the body due to the step-movement 

 showed that, with a speed of 76 meters per minute, one of their sub- 

 jects, weighing 73 kg., expended 0.65 calorie in this work, that is, 23 

 per cent of the increase in metabolism over the standing requirements 

 was due to this work of step-elevation. 



Waller, 3 in a series of reports on the physiological cost of various 

 forms of muscular work, included a few experiments on horizontal 

 walking. Computations show that his results for speeds of approxi- 

 mately 100 meters per minute yield somewhat over 0.8 gram-calorie 

 per horizontal kilogrammeter. Running at a speed of approximately 

 200 meters per minute gave a heat-production of about 1.3 gram- 

 calories per horizontal kilogrammeter. The first value is measurably 



1 Brezina and Reichel, Biochem. Zeitschr., 1914, 63, p. 170. 



2 Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915, pp. 79 and 87. 

 3 Waller, Journ. Physiol., 1919, 53, Proc. Physiol. Soc., p. xxiv; see, also, Journ. Physiol., 1919, 

 52, Proc. Physiol. Soc., p. Ixxii. 



