Oxidative removal of lactate after strenuous exercise

Metabolic fate of lactate after strenuous exercise which lasted 2-3 min was investigated in rats and mice. 14C-labeled lactate or glucose was injected into the aorta of rats through an catheter. 14C-glucose was injected intraperitoneally into the mice after supramaximal exercise. The mice ran twice with a 4 hr interval to investigate muscle 14C-lactate metabolism which was produced from muscle 14C-glycogen. A great deal of blood and muscle 14C-lactate was expired as 14CO2 after the exercise. The results indicate that oxidative removal is the major fate of lactate metabolism after strenuous exercise and that blood glucose is the major substrate for muscle glycogen resynthesis. Light intensity exercise after strenuous exercise (active recovery) enhances oxidative removal of blood and muscle lactate. Gluconeogenesis from lactate to glycogen within the skeletal muscle is not a major pathway of muscle lactate metabolism, while high intensity training can activate this pathway.