EFFECT OF ENDURANCE TRAINING ON FATTY-ACID METABOLISM - LOCAL ADAPTATIONS

Older studies of humans seem to suggest a correlation bem een free fat ty acid (FFA) turnover and oxidation on the one hand and plasma FFA co ncentration on the other hand during submaximal exercise. However, rec ent studies, in which higher concentrations of plasma FFA have been re ached during prolonged submaximal exercise, have revealed a levelling off in net uptake in spite of increasing plasma FFA concentrations. Fu rthermore, this relationship between FFA concentration and FFA uptake and oxidation is altered by endurance training. These recent findings in humans support the notion from other cell types that transmembrane fatty acid transport is not only by simple diffusion, but predominantl y carrier-mediated. During prolonged submaximal knee-extension exercis e it has been demonstrated that the total oxidation of fatty acids was approximately 60% higher in trained subjects than in nontrained subje cts, The training-induced adaptations responsible for this increased u tilization of plasma fatty acids by the muscle could be located at sev eral steps from the mobilization of fatty acids to skeletal muscle met abolism in the mitochondria. In this paper regulation at the transport steps and also at Various metabolic steps is discussed.