Glucose oxidation and replacement during prolonged exercise in man.

Abstract

Blood glucose turnover rate and oxidation have been examined during prolonged physical exercise. Uniformly labeled glucose-14C was administered as a single injection after 9 hr. of treadmill walking, and observations were made during an additional 4.5-hr, period of exercise. Glucose turnover rate was 206 mg/kg per hr., glucose oxidation rate was 175 mg/kg per hr., and 17% of total CO2 production was derived from the oxidation of glucose. In resting subjects, glucose turnover rate was 140 mg/kg per hr., glucose oxidation was 79 mg/kg per hr., and 33% of total CO2 production was derived from glucose metabolism. The incorporation of various precursors into the blood glucose was examined. The incorporation of carbon from palmitate, alanine, and glycerol into glucose was similar during rest or exercise. The data suggest that relatively more lactate was recycled into glucose during exercise than at rest.