590 



JOHX R. MURLIK 



tations for the corresponding increase of ten revolutions gives from 90 to 

 100 revolutions 11.94 per cent, and from 120 to 130 revolutions 7.82 per 

 cent, with intermediate values in percentage for the intervening incre- 

 ments. Net efficiency showed a similar falling off with the higher rates of 

 speed. For example, when the effective muscular work was 1.95 calories 

 per minute, at a rate of 90 revolutions the net efficiency was 22.G per cent, 

 while at 124 revolutions per minute it was only 15.7 per cent. 



3. Relative Value of Different Foodstuffs as a Source of Energy in 

 Muscular Work. From his experiments upon Tissot as subject in climb- 

 ing and descending stairs, Chauveau came to the conclusion from a con- 

 sideration of the respiratory quotients, that carbohydrate alone furnishes 

 the energy of muscular work and that fat can only be utilized by first 

 undergoing transformation to carbohydrate. Zuntz and Heinemann, how- 

 ever, point out that if Chauveau's hypothesis of transformations were 

 true, 30 per cent more energy for each unit of work performed should 

 be liberated when fat burns than when carbohydrate is the starting point. 

 Zuntz further criticizes Chauveau's experiments as being too extreme 

 in severity (the subject was exhausted at the end of 70 minutes) and 

 not of sufficient duration. Experiments by himself and associates in 

 which precautions in both respects were carefully observed gave respiratory 

 quotients during work which were exactly the same as in muscular rest. 

 He cites especially the following results of Heinemann made with the 

 Gartner ergostat and the Zuntz respiration apparatus. 



TABLE 14 

 ENERGY PRODUCTION OF MUSCULAR WORK ox DIFFERENT DIETS (Heinemann) 



It appears from this comparison that there really is little difference between 

 fat and carbohydrate, and that protein likewise as the chief constituent of 

 a diet occupies a place only a little less favorable as a source of muscular 

 energy. The respiratory quotients were the same for each foodstuff dur- 

 ing muscular work as during rest. 



This last statement seems to be true, however, only with the moderate 

 intensity of work which Zuntz observed. Benedict and Cathcart found 

 the average respiratory quotients with their professional bicycle rider 

 were as follows: 



