THE EFFECT OF MUSCULAE WOEK ON METABOLISM 687 



exchanges due to protein metabolism will give the proportions of fat and 

 carbohydrate oxidised. The following Table gives the relative combustion 

 of carbohydrate and fat for a given respiratory quotient : 



R.Q. Carbohydrate Fat 



1-00 . . . 100 per cent. . per cent. . 5-047 

 0-95 . 83 17 4-985 



0-90 ... 66 .34 



0-85 ... 49 .51 



0-80 . . . 32 .68 



0-75 ... 15 .85 



0-707 . 100 



4-924 

 4-863 

 4-801 

 4-739 

 4-686 



Since we know the amount of heat given off on oxidation of each gramme 

 of carbohydrate or fat metabolised in the body, we can now measure 

 accurately the total energy available from the chemical changes thus deter- 

 mined. The number of Calories set free in the body for every litre of oxygen 

 taken in are also given in the above table. 



It will be noticed that in contradiction to popular opinion the proteins do not play 

 any special part in relation to muscular exercise. The special value of protein is for 

 building up the body and for repairing directly wear and tear. As a source of energy 

 it presents no advantages over carbohydrate and fat; in fact, it may be in some 

 respects inferior to this latter substance or, at any rate, less economical, owing to the 

 fact that ingestion of protein causes an increased metabolism, the whole of which 

 appears in the form of heat. If an animal after a protein meal be made to work, the 

 increased metabolism due to the specific dynamic action of the protein is still observed 

 over and above that due to the performance of work. The output of energy of a man 

 on a large meat diet doing a certain amount of work will therefore be greater than 

 if the same amount of work were performed on a diet consisting largely of carbo-. 

 hydrates and fats. On the other hand, in training we have to consider not only the 

 performance of work done during the training, but also the necessity of building up 

 the muscular tissues of the body. Under these conditions therefore, there is some 

 reason for a plentiful supply of protein in the diet. When however a man has to 

 undertake a certain amount of muscular exercise every day and has arrived at the 

 full development of his muscular system, there is no need to attempt to supply the 

 energy for his movements at the expense of foods rich in protein, such as meat. In 

 many cases the beneficial effects of so-called meat are due to its content in fat this 

 foodstuff presenting advantages over carbohydrates when large quantities have to 

 be ingested to supply the daily energy requirements of the body. 



