THE NATURE OF THE FOODSTUFFS OXIDIZED TO PROVIDE ENERGY IN MUSCULAR EXERCISE

Abstract

In an 11-kgm. dog a protein metabolism as nearly exclusive as possible was established to see whether during exercise on a horizontal treadmill the dog still continued to use protein as at rest, the R.Q. was determined by Benedict-Homans apparatus. Since the R.Q. of a mixture of carbohydrate and fat can approximate that of protein, it was necessary first to create a one-sided metabolism of either carbohydrate or fat, so that this might be differentiated from the ensuing protein metabolism. The attempt was therefore made (1) to approach a theoretic R.Q. of 0.71 by fat-feeding or starvation, or of 1.00 by carbohydrate feeding, on days preceding the exp. (2) to give an amt. of lean beef heart on the experimental day that would result in an exclusive or nearly exclusive protein metabolism at rest, as shown by a shift of the R.Q. to that of protein; (3) then to exercise the animal and see whether the R.Q. of exercise and recovery remained that of protein, or reverted to the prevailing quotient before the meat feeding. The results indicate that protein is a normal source of oxidative energy for muscular exercise, and its non-nitrogenous split products are as readily available for this purpose as are carbohydrate and fat.