Timing of amino acid-carbohydrate ingestion alters anabolic response of muscle to resistance exercise.
Level 2 - randomized trial
Randomized crossover trial in humans
PubMed 11440894 · doi:10.1152/ajpendo.2001.281.2.E197
What was done
Six healthy human subjects participated in a randomized crossover study evaluating an oral essential amino acid-carbohydrate supplement consumed immediately before resistance exercise (PRE) versus immediately after exercise (POST). Net leg uptake, concentrations, and enrichments of phenylalanine were assessed using a primed continuous infusion of L-[ring-2H5]phenylalanine, femoral arteriovenous catheterization, and vastus lateralis muscle biopsies.
What was found
Blood and muscle phenylalanine concentrations increased by approximately 130% following supplement consumption in both conditions. Amino acid delivery to the leg was significantly greater in PRE than in POST during the exercise bout and across the first post-exercise hour (P < 0.05). Total net phenylalanine uptake across the leg was significantly higher in PRE (209 +/- 42 mg) than in POST (81 +/- 19 mg, P = 0.0002). Phenylalanine disappearance rate increased after ingestion in both trials.
Why it matters
This study shows that timing amino acid-carbohydrate intake immediately before resistance training enhances acute net muscle protein synthesis more than post-exercise intake, primarily driven by exercise-induced increases in amino acid delivery to working muscle.
Limits
The sample size was very small (n = 6), and subject characteristics such as sex, age, and training background are not specified in the abstract. Only acute tracer kinetics over a short window were measured; chronic training adaptations in muscle mass and strength were not evaluated.
Cited by
- supports Taking essential amino acids prior to exercise increases the delivery of amino acids into muscle tissue due to increased exercise-induced blood flow.