By Jessica Patella, ND, abstracted from “Leucine-enriched essential amino acid supplementation during moderate steady state exercise enhances post-exercise muscle protein synthesis.” In the July 2011 issue of The American Journal of Clinical Nutrition.
The effects of resistance exercise, such as weight lifting, on muscle growth have been well studied (1). Muscle protein growth can last up to 48 hours after resistance exercise and supplementation of essential amino acids enhances this growth (1-3). However, there is little research on the effects of endurance exercise, such as long distance running, on muscle growth (1). A recent study published in The American Journal of Clinical Nutrition was one of the first studies to suggest supplementing with leucine-enriched essential amino acids during endurance exercise can increase muscle growth recovery (1).
The research included 10 active-duty military that participated regularly in endurance (running and marching) and resistance (weight lifting) exercise (1). The researchers tested to see if there was a difference in consuming an essential amino acid supplement (EAA) or an essential amino acid supplement enriched with leucine (L-EAA) (1). The study was a 13-day randomized crossover study, meaning the participants took both the EAA and the L-EAA with a one-week washout period in between (1), during which they did not take any supplements.
Participants underwent a 60-minute steady endurance exercise on a cycle (approximately 60% VO2 peak). During the exercise, participants drank 125 mL of either L-EAA or EAA supplement in 20-minute intervals during the entire 60 minutes of exercise (1). Muscle biopsy samples were then taken 30 minutes and 210 minutes after exercise. The L-EAA drink contained 3.5g of leucine and the EAA drink contained 1.87g leucine. Both drinks contained a total of 10g of essential amino acids (1).
Post-exercise muscle growth (muscle protein synthesis) was 33% higher with the L-EAA supplement (0.08 +/- 0.01%/h) compared to the EAA supplement (0.06 +/- 0.01%/h; P<0.05). And blood concentrations of leucine were 31% greater with the L-EAA supplement (232 +/- 15 micromol/L) compared to the EAA (176 +/- 13 micromol/L; P<0.05) (1).
This was the first study to show taking leucine during endurance exercise increased muscle growth in recovery. Previous studies supplemented leucine at rest and after exercise and did not show any increased muscle growth (1). It is likely that supplementing L-EAA during exercise spared the protein stores in the body more than EAA, which lead to greater muscle growth during recovery (1).
In conclusion, supplementing with a leucine-enriched essential amino acid drink throughout endurance exercise increased muscle growth. This is important for populations susceptible to muscle loss. Further research with more participants needs to be conducted to confirm the results.
Jessica Patella, ND, is a naturopathic physician specializing in nutrition and homeopathic medicine. She earned her ND from Southwest College of Naturopathic Medicine in Tempe, AZ and is a member of the North Carolina Association of Naturopathic Physicians. Visit her website at www.awarenesswellness.com.
1. Pasiakos S, et al. Leucine-enriched essential amino acid supplementation during moderate steady state exercise enhances post-exercise muscle protein synthesis. Am J Clin Nutr 2011; 94: 804-18.
2. Phillips SM, et al. Mixed muscle protein synthesis and breakdown after resistance exercise in humans. Am J Physiol 1997; 273: E99-107.
3. Dreyer HC, et al. Leucine-enriched essential amino acid and carbohydrate ingestion following resistance exercise enhances mTOR signaling and protein synthesis in human muscle. Am J Physiol Endocrinol Metab 2008; 294: E392-400.