Plasma Lipoproteins, Hormones, and Energy Substrates During the First Days After Prolonged Exercise*

Abstract

To elucidate the delayed metabolic changes after prolonged exercise, 18 moderately trained young subjects participating in a 3-h running test were examined. Running speed during the test corresponded to 77 ± 61 (mean ± SD)% of the speed at which the blood lactate reached 4 mmol/l. Fasting blood samples were obtained 1 day before, immediately before, and 1, 2, 4, and 8 days after the race. Lipoprotein fractions were isolated by ultracentrifugation and analyzed for cholesterol and triglyceride concentration. One day after the race, total, VLDL, and LDL cholesterol as well as total and VLDL triglycerides were significantly decreased, and the Intralipid disappearance rate constant measured in six subjects was significantly increased compared to 1 day before the race.

On the first post-exercise day, the basal insulin concentrations were significantly lowered. Glucagon, Cortisol, and human growth hormone showed no significant changes. One day after exercise, free fatty acids, acetoacetate, and 3-hydroxybutyrate were significantly elevated.

Lowered triglyceride levels 1 day after exercise could be caused by an enhanced peripheral triglyceride clearance rate and possibly by a reduced hepatic triglyceride synthesis in which low insulin levels could play a regulatory role.

Key words

lipoproteins - insulin - glucagon - free fatty acids - acetoacetate - 3-hydroxybutyrate - intravenous fat tolerance test - exercise