RESEARCHES BY OTHER INVESTIGATORS. 



walking on a level. These served the dual purpose of (a) supplying 

 a suitable base-line for the proper study of the special factors involved 

 in grade walking, and (6) supplementing to a not inconsiderable 

 extent the present knowledge regarding the physiology of horizontal 

 walking. Additional data have been collected on the changes in the 

 pulse-rate, respiration-rate, the pulmonary ventilation, and body- 

 temperature as affected by the intensity of the work in both horizontal 

 and grade walking, and their relation to the energy expended. 



RESEARCHES BY OTHER INVESTIGATORS ON ENERGY 

 REQUIREMENTS FOR WALKING. 



HORIZONTAL WALKING. 



The earlier studies of the energy metabolism during horizontal 

 walking have been reviewed by Durig 1 and by Benedict and Mursch- 

 hauser. 2 One of the mam subjects of interest in this work is the 

 determination of the energy cost per horizontal kilogrammeter, i. e., 

 the energy cost of the movement of 1 kilogram 1 meter in a horizontal 

 direction. The earlier studies were made under various conditions 

 of rest, food, altitude, speed of walking, and methods of computation 

 as regards the basal value. In consequence, the results vary widely, 

 Benedict and Murschhauser in their summary table noting average 

 values ranging from 0.308 to 1.169 gram-calories per horizontal kilo- 

 grammeter. Durig showed that when the rate of walking was limited 

 to moderate speeds and the subject was in the post-absorptive condi- 

 tion, the energy expenditure was very close to 0.55 gram-calorie per 

 horizontal kilogrammeter, but when the speed exceeded a certain 

 degree, given by Durig as approximately 80 meters per minute, the 

 energy cost per horizontal kilogrammeter increased. This limiting 

 speed Durig termed the "maximal economic velocity." Reichel, 3 in 

 Durig's laboratory, gave a mathematical formula to this generalization, 

 and Durig further states that for each meter in excess of the maximal 

 economic velocity, the energy metabolized increases from 1.2 to 1.5 

 per cent of the normal value. 



In continuation of Durig's work and employing his well-established 

 methods, Brezina and Kolmer 4 conducted experiments on horizontal 

 walking with and without load at varying velocities. In these studies 

 the authors confirmed the results of Durig in relation to the absence 

 of the effects of speed below the maximal economic velocity, and add 

 that this value is independent of a load up to 21 kg., that is, a dead 



^urig, Denkschr. d. math.-natur. Klasse d. kaiserl. Akad. d. Wissensch., 1909, 86, p. 250. 

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

 3 See Durig, Denkschr. d. math.-natur. Klasse d. kaiserl. Akad. d. Wissensch., 1909, 86, pp. 

 278 and 279. 



4 Brezina and Kolmer, Biochem. Zeitschr., 1912, 38, p. 129. 



