The metabolism of the diabetic individual during and after muscular exercise

Publisher Website
Google Scholar
Abstract
Muscular exercise in the diabetic individual appears to be accompanied by the same metabolic changes as in the normal. The curves of recovery O2 intake and of CO2 output are similar to those of normal men, both for mild and for more strenuous exertion. The increase in lactic acid in the blood attained value as high as in normal men performing similar exercise. There is no unusual delay in the removal of this lactic acid. Exercise increases the combustion of carbohydrate in the diabetic. For short periods of exercise, with insulin administered during the last 17 hrs., the respiratory quotient of the excess metabolism is unity, exactly as in normal men while for exercise of long duration it tends to fall towards that of the previous resting metabolism. In this respect the diabetic individual, with recent insulin on a diet poor in carbohydrate, behaves in a manner exactly similar to a normal man on a diet consisting mainly of fat. The phenomena, however, are even more exaggerated than in such a normal individual. In a diabetic individual long without insulin the respiratory quotient of the excess metabolism is low, even for short periods of exercise. The simplest way of regarding the matter is to suppose that a muscle, for its oxidative processes in recovery from exertion, uses carbohydrate only: that in the presence of insulin there are stores of carbo-hydrate in a form readily available for use by the muscle, and that a short interval of exercise does not sufficiently deplete these stores to require recourse to other substances in the body. In the absence of insulin these ready stores of carbohydrate have run low, so that even brief exercise stimulates the metabolic processes of the body to restore the reserves of carbohydrate. Three factors, prolonged muscular exertion, a diet poor in carbohydrate, and absence of insulin, produce the same effect, namely, a lowering of the respiratory quotient of the excess metabolism due to exercise. The hyper-glycemia following ingestion of food in the diabetic is reduced rather abruptly by a bout of exercise. This result, however, occurs only when insulin is available; in its absence the fall in blood-sugar on exercise is no more rapid that at rest. An approximate calculation has been made, from the lowering of the blood-sugar concentration, of the amount of sugar which has disappeared from the whole body in excess of that lost in a like resting interval. The quantity so measured is of the same order as the amount of sugar burnt, calculated from the excess 0 intake and the R. Q. The sugar which has disappeared seems rather larger than that which has undergone oxidation. The data available for the calculations are rough, and it is possible that the disappearance of sugar, following exercise, may be attributed simply to oxidation. With a sufficient supply of insulin in the tissues of a diabetic a more complete combustion of fat takes place on exercise than at rest. Without available insulin exercise may at times result in an increased production of ketones.

This publication has 8 references indexed in Scilit: