There's not quite as much research out there on leucine and endurance performance as I'd have hoped, but I did find a few studies that I want to highlight.
Recovery & Subsequent Performance
In one study, researchers compared two recovery meals consumed after 2.5 hours of cycling intervals. One of the recovery meals provided a higher amount of leucine/protein compared to the other meal (but both contained sufficient carbohydrate and were equal in calories). After a day and a half of rest, the cyclists repeated a sprint performance test. The researchers found that those who had the recovery meal with higher amounts of leucine/protein experienced a 2.5% increase in sprint power and a 13% decrease in perceived tiredness during the sprints (Thomson et al, 2011). However, another study found that leucine intake post-exercise did not improve subsequent sprint performance or power –although it did reduce muscle tissue damage (Nelson et al, 2012).
Another study found that among trained canoeists, 6 weeks of leucine supplementation led to increased upper body power and work, increased total rowing time to exhaustion, and a decreased rate of perceived exertion (Crowe et al, 2006).
Other researchers have examined the impact on leucine intake during exercise. For example, Pasiakos et al (2011) compared the effects of two essential amino acid drinks – one with a higher leucine concentration – on fit adults during cycling exercise. They found that muscle synthesis protein synthesis was greater after using the leucine enhanced drink. However, there are several issues with this study –the primary one being that no control group was used. In addition, we know that proper recovery methods after exercise enhance muscle protein synthesis – so the research is unclear about whether it is of any use during exercise.
Based on the research, it appears that leucine may be helpful with recovery and muscle protein synthesis after an endurance exercise session when used as part of the recovery meal/snack. It is possible that it may also help with subsequent performance when used in recovery. There doesn't appear to be enough research suggesting a performance benefit when used during exercise, though.
Also - there is no reason to spend money on pricey supplements, as selecting the correct food choices can provide all the leucine (and other amino acids) you need! For example, in the canoeist study, the athletes were supplemented with 45 milligrams leucine per kilogram of body weight. For a 68 kilogram (150 pound) athlete, that’s about 3060 milligrams – or 3 grams. And remember, this was the total per day, not just in their recovery meals.
If you take a look at our chart below, you’ll see it’s easy to get that much each day by making choices consistent with recommendations for an athlete’s diet!
After long endurance exercise sessions, you should be replenishing your body with mostly carbohydrates to replace muscle glycogen synthesis as well as a moderate amount of protein. The “ideal ratio” is about 3:1 or 4:1 carbohydrates to protein, although don’t worry about getting too tied down in this – just realize that the carbohydrate should be making up a larger portion of your recovery snack/meal than the protein.
The protein in the recovery food helps increase muscle glycogen synthesis if you are not getting enough carbohydrate, and also helps with muscle recovery and protein synthesis. 15 to 25 grams of protein after a long exercise session is appropriate and you can choose protein foods with higher amounts of leucine from the list above to maximize recovery.
If you find using protein powders helpful and convenient in your recovery meals, a whey protein powder will provide a good amount of leucine. However, keep in mind that there may be quality control issues with many protein powders and that these powders are often more expensive compared to regular foods.
- Crowe MJ, Weatherson JN, Bowden BF. (2006). Effects of dietary leucine supplementation on exercise performance. Eur J Appl Physiol; 97(6):664-72. Retrieved from: http://www.ncbi.nlm.nih.gov/pubmed/16265600
- Nelson AR, Phillips SM, Stellingwerff T, Rezzi S, Bruce SJ, Breton I, Thorimbert A, Guy PA, Clarke J, Broadbent S, Rowlands DS. (2012). A protein-leucine supplement increases branched-chain amino acid and nitrogen turnover but not performance. Med Sci Sports Exerc; 44(1):57-68. Retrieved from: http://www.ncbi.nlm.nih.gov/pubmed/21685813
- Pasiakos SM, McClung HL, McClung JP, Margolis LM, Andersen NE, Cloutier GJ, Pikosky MA, Rood JC, Fielding RA, Young AJ. (2011). Leucine-enriched essential amino acid supplementation during moderate steady state exercise enhances postexercise muscle protein synthesis. Am J Clin Nutr; 94(3):809-18. Retrieved from: http://ajcn.nutrition.org/content/94/3/809.long
- Thomson JS, Ali A, Rowlands DS. (2011). Leucine-protein supplemented recovery feeding enhances subsequent cycling performance in well-trained men. Appl Physiol Nutr Metab; 36(2):242-53. doi: 10.1139/h10-104. Retrieved from: http://www.ncbi.nlm.nih.gov/pubmed/21609286