EFFICIENCY IN GRADE WALKING. 



251 



these men (omitting A. J. O.) lie so close together that no statement 

 may be made regarding superiority. The fact that E. D. B. stands 

 somewhat above the others may be accounted for by the relatively 

 large number of experiments in which there was a small amount of 

 work. As has been stated, in all such experiments the subjects show a 

 higher efficiency than in those with a greater amount of work. There 

 is hardly sufficient ground in the small difference for E. D. B. to suppose 

 that as an individual he was any more efficient than the other four men. 



TABLE 70. Efficiency of subjects in grade-walking experiments. 



Many reports on the mechanical efficiency of men doing various 

 forms of work have been published. One of the earliest was that of 

 Edward Smith, 1 who used a tread- wheel and from whose results 

 Helmholtz 2 computed a gross efficiency of 20 per cent. 



A large amount of work on the energy exchange in man during walk- 

 ing has been done by both Zuntz and Durig and their associates, to 

 which reference has already been made. (See pp. 8 to 13.) In the 

 summary of the results 3 given in table 71 and obtained with men walk- 

 ing on a treadmill at grades of 12.68 to 36.2 per cent, the net efficiencies 

 range from 25.7 to 46.5 per cent, with a distinct tendency to approach 

 33 per cent. This is in close accord with our results. 



The efficiencies of men performing other kinds of work, such as using 

 a wheel and brake, lifting weights, and riding a stationary bicycle, 

 have been studied by a number of investigators, and then- results have 

 been discussed by Benedict and Cathcart. 4 In many cases there is no 

 clear distinction between the "gross" and "net" efficiency, and in 

 several studies only the carbon-dioxide output is determined. Natur- 

 ally, these results show considerable variation, depending upon the 

 subject, the form of work, and not infrequently upon the method of 



, Edward, Phil. Trans., 1859, 149, p. 681. 

 2 Helmholtz, Proc. Roy. Inst., 1861, 3, p. 347. 



3 Drawn from Durig, Denkschr. d. math, natur. Klasse d. kaiserl. Akad. d. Wissensch., 1909, 

 86, p. 299. 



4 Benedict and Cathcart, Carnegie Inst. Wash. Pub. No. 187, 1913, p. 101. 



