588 JOHN E. MURLIN 



The German laboratories which have contributed most to the literature 

 of mechanical efficiency in muscular work are those of N. Zuntz and of 

 Kronecker. Both used the method of Zuntz in determining the respiratory 

 exchange. Magnus-Levy (#), Durig (c), and Loewy (a), all of the Zuntz 

 school of workers, have given important summaries of this work up to 1911. 

 Dung's own experiments under Kronecker's direction, as well as those of 

 Zuntz, and Loewy, Miiller(c), Caspari(a), Zuntz and Schumburg(a), and 

 L. Zuntz, show plainly the effect of training upon muscular efficiency, as 

 well as the influence of velocity. Much of the work was done with the tread- 

 mill, some with an arm ergometer and other experiments in which the res- 

 piratory exchange was measured by means of the Zuntz portable apparatus 

 was done in marching on roads or climbing mountain trails. The treadmill 

 showed net efficiencies as high as 37 per cent, with the average at 31 per 

 .cent. The arm ergometer gave the lowest efficiency, namely, 19 per cent 

 and the mountain climbing and inarching experiments intermediate results. 

 In certain experiments of the latter class carried out in summer upon a 

 mountain trail which had an inclination of 16.4 per cent Durig's own ef- 

 ficiency was 31.1 per cent and that of his.three companions was 30.3, 31.7 

 and 30.1 per cent respectively. In bicycle riding L. Zuntz, who was the 

 first to make studies of the respiratory exchange in this type of work, found 

 values which later were calculated to show a net efficiency of 28 per cent 

 (Berg, DuBois-Reymond and Zuntz, L.). Benedict and Carpenter, using 

 the same type of work but changing the bicycle to a stationary ergometer, 

 found an average of only 21.5 per cent, a figure which has been substan- 

 tially confirmed by a more recent *and extensive study by Benedict and 

 Cathcart. 



The effect of training is shown in the following table from Benedict and 

 Cathcart exhibiting the maximum gross and net efficiencies for their six 

 subjects. The highest efficiency in both senses is shown by the one pro- 

 fessional bicycle rider (M.A.M.) of the group. 



TABLE 13 



MAXIMUM GROSS AND NET EFFICIENCIES WITH THE BICYCLE ERGOMETER (Benedict and 



Cathcart) 



Benedict and Cathcart have also given attention to the relation of speed 

 to muscular efficiency. They find that while in general the efficiency in- 

 creases with the load (amperage of current actuating the brake) with 



