POST-EXERCISE KETOSIS

The findings support the following hypothesis regarding the nature of post-exercise ketosis: in severe exercise the need for respiratory fuels is increased, and adipose-tissue triglyceride is mobilised as an alternative fuel to glucose, as indicated by the rise of blood-glycerol and plasma-F.F.A. in the blood-plasma.

Abstract

The effects of ingestion of glucose after strenuous exercise on the concentrations of blood glucose, glycerol, and ketone-bodies, and plasma-free-fatty-acids (F.F.A.) have been studied in a group of twelve subjects. The results have been compared with those of oral glucose-tolerance tests at rest in eight of the same subjects and after administration of glucose to three subjects undergoing a prolonged fast (72 hours). The findings support the following hypothesis regarding the nature of post-exercise ketosis. In severe exercise the need for respiratory fuels is increased, and adipose-tissue triglyceride is mobilised as an alternative fuel to glucose, as indicated by the rise of blood-glycerol and plasma-F.F.A. The increased concentration of F.F.A. and the depletion of hepatic glycogen cause an increased rate of ketone-body formation by the liver because in this situation ketone-body production is approximately proportional to the concentration of F.F.A. in the blood-plasma. During the exercise the extra ketone bodies formed also serve as a fuel of respiration and therefore do not accumulate. After cessation of exercise the raised concentration of F.F.A. results in a continued high rate of ketone-body formation which shows itself as post-exercise ketosis. The rise in the concentrations of F.F.A. with exercise modifies the glucose-tolerance curve, which shows a higher peak and a delayed fall, presumably because F.F.A. competes with glucose as a fuel of respiration and thus inhibits glucose utilisation.