106-111-Van Loon

Background: Postexercise muscle glycogen synthesis is an important factor in determining the time needed to recover from prolonged exercise. Objective: This study investigated whether an increase in carbohydrate intake, ingestion of a mixture of protein hydrolysate and amino acids in combination with carbohydrate, or both results in higher postexercise muscle glycogen synthesis rates than does ingestion of 0.8 g · kg21 · h21 carbohydrate, provided at 30-min intervals. Design: Eight trained cyclists visited the laboratory 3 times, during which a control beverage and 2 other beverages were tested. After the subjects participated in a strict glycogen-depletion protocol, muscle biopsy samples were collected. The subjects received a beverage every 30 min to ensure ingestion of 0.8 g carbohydrate ·kg21 ·h21 (Carb trial), 0.8 g carbohydrate ·kg21 ·h21 plus 0.4 g wheat protein hydrolysate plus free leucine and phenylalanine ·kg21 ·h21 (proven to be highly insulinotropic; Carb + Pro trial), or 1.2 g carbohydrate · kg21 · h21 (Carb + Carb trial). After 5 h, a second biopsy was taken. Results: Plasma insulin responses in the Carb + Pro and Carb + Carb trials were higher than those in the Carb trial (88 ± 17% and 46 ± 18%; P < 0.05). Muscle glycogen synthesis was higher in both trials than in the Carb trial (35. 4 ± 5.1 and 44.8 ± 6.8 compared with 16.6 ± 7.8 mmol glycosol units · g dry wt21 · h21, respectively; P < 0.05). Conclusions: Addition of a mixture of protein hydrolysate and amino acids to a carbohydrate-containing solution (at an intake of 0.8 g carbohydrate · kg21 · h21) can stimulate glycogen synthesis. However, glycogen synthesis can also be accelerated by increasing carbohydrate intake (0.4 g · kg21 · h21) when supplements are provided at 30-min intervals. Am J Clin Nutr 2000;72:106–11.