502 



JOHN R. MURLIN 



waste of energy from fat in these experiments works out as eight 

 per cent. 



The last-named authors have carried the comparison between fat and 

 carbohydrate as a source of muscular work much farther. They devised 

 experiments upon human subjects with the bicycle ergometer of Krogh 

 placed inside a Jaquet-Grafe (page 520) respiratipn chamber, which would 

 be done, after the manner of Benedict and Cathcart's experiments, before 

 the first meal of the day, but following two or more days upon controlled 

 diets containing in turn a decided preponderance of the two non-nitro- 

 genous foodstuffs. The two most successful subjects were college athletes 

 familiar with bicycling, and, in one series, freshly trained. Both these 

 students and three out of five older subjects experienced great difficulty in 

 doing the prescribed work and suffered much fatigue thereafter following 

 heavy fat feeding, but did the work with ease and without fatigue follow- 

 ing carbohydrate. This experience accords with that of other observers. 



The results of Krogh and Lindhard are summarized below. 



TABLE 15 



COMPARISON OF I AT AND CARBOHYDRATE AS SOURCE OF MUSCULAR ENERGY 

 (Krogh and Lindhard) 



The simple average of the percentage differences, the authors state, would 

 be very misleading partly because of the different number of experiments 

 for the different subjects and partly because the several series are by no 

 means equally concordant. By assigning definite "weights" to each series 

 in proportion to the number of determinations and in inverse ratio to the 

 standard deviations within each series the average percentage waste of 

 energy from fat as compared with carbohydrate is 11.25. It follows 

 clearly that work is more economically performed on carbohydrate than 

 on fat. 



From the table it may be seen that the net expenditure of energy neces- 

 sary to perform one calorie of mechanical work on the ergometer varies 



