Timing of amino acid-carbohydrate ingestion alters anabolic response of muscle to resistance exercise

The present study was designed to determine whether consumption of an oral essential amino acid-carbohydrate supplement (EAC) before exercise results in a greater anabolic response than supplementation after resistance exerci se. Six healthy human subjects participated in two trials in random order, PRE (EAC consumed immediately before exercise), and POST (EAC consumed imme diately after exercise). A primed, continuous infusion of L-[ ring-(2) H-5] phenylalanine, femoral arteriovenous catheterization, and muscle biopsies from the vastus lateralis were used to determine phenylalanine concentratio ns, enrichments, and net uptake across the leg. Blood and muscle phenylalan ine concentrations were increased by similar to 130% after drink consumptio n in both trials. Amino acid delivery to the leg was increased during exerc ise and remained elevated for the 2 h after exercise in both trials. Delive ry of amino acids (amino acid concentration times blood flow) was significa ntly greater in PRE than in POST during the exercise bout and in the 1st h after exercise (P< 0.05). Total net phenylalanine uptake across the leg was greater (P = 0.0002) during PRE (209 +/- 42 mg) than during POST (81 +/- 1 9). Phenylalanine disappearance rate, an indicator of muscle protein synthe sis from blood amino acids, increased after EAC consumption in both trials. These results indicate that the response of net muscle protein synthesis t o consumption of an EAC solution immediately before resistance exercise is greater than that when the solution is consumed after exercise, primarily b ecause of an increase in muscle protein synthesis as a result of increased delivery of amino acids to the leg.