Impaired muscle glycogen resynthesis after a marathon is not caused by decreased muscle GLUT-4 content

Abstract

Asp, Sven, Thomas Rohde, and Erik A. Richter. Impaired muscle glycogen resynthesis after a marathon is not caused by decreased muscle GLUT-4 content. J. Appl. Physiol. 83(5): 1482–1485, 1997.—Our purpose was to investigate whether the slow rate of muscle glycogen resynthesis after a competitive marathon is associated with a decrease in the total muscle content of the muscle glucose transporter (GLUT-4). Seven well-trained marathon runners participated in the study, and muscle biopsies were obtained from the lateral head of the gastrocnemius muscle before, immediately after, and 1, 2, and 7 days after the marathon, as were venous blood samples. Muscle GLUT-4 content was unaltered over the experimental period. Muscle glycogen concentration was 758 ± 53 mmol/kg dry weight before the marathon and decreased to 148 ± 39 mmol/kg dry weight immediately afterward. Despite a carbohydrate-rich diet (containing at least 7 g carbohydrate ⋅ kg body mass−1 ⋅ day−1), the muscle glycogen concentration remained 30% lower than before-race values 2 days after the race, whereas it had returned to before-race levels 7 days after the race. We conclude that the total GLUT-4 protein content is unaltered in the lateral gastrocnemius after a competitive marathon and that the slow recovery of muscle glycogen after the race apparently involves factors other than changes in the total content of this protein.