Effect of prior exercise on glucose metabolism in trained men

Several studies have demonstrated that oral glucose tolerance is impaired in the immediate postexercise period. A double-tracer technique was used to examine glucose kinetics during a 2-h oral glucose (75 g) tolerance test (OGTT) 30 min after exercise (Ex, 55 min at 71±2% of peak O₂ uptake) and 24 h after exercise (Rest) in endurance-trained men. The area under the plasma glucose curve was 71% greater in Ex than in Rest (P=0.01). The higher glucose response occurred even though whole body rate of glucose disappearance was 24% higher after exercise (P=0.04, main effect). Whole body rate of glucose appearance was 25% higher after exercise (P=0.03, main effect). There were no differences in total (2 h) endogenous glucose appearance (R_aE) or the magnitude of suppression of R_aE, although R_aE was higher from 15 to 30 min during the OGTT in Ex. However, the cumulative appearance of oral glucose was 30% higher in Ex (P=0.03, main effect). There were no differences in glucose clearance rate or plasma insulin responses between the two conditions. These results suggest that adaptations in splanchnic tissues by prior exercise facilitate greater glucose output from the splanchnic region after glucose ingestion, resulting in a greater glycemic response and, consequently, a greater rate of whole body glucose uptake.