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What are BCAAs?

Proteins are made from 20 amino acids, some of which the body can make itself (non-essential) and some of which must be consumed in the diet (essential). The branched chain amino acids (BCAAs) are the three essential amino acids of leucine, isoleucine and valine. Together, they make up 35% of the essential amino acids contained in muscles(1). They are ‘essential’ because they must be consumed in the diet, as the body cannot make them out of other amino acids. BCAAs are naturally found in foods that are high in protein, with the highest concentrations found in animal protein, including meat and dairy foods.


Why the BCAA Shot?

The Science in Sport BCAA shot has been formulated to support performance by minimising muscle protein breakdown during exercise. It has been well documented that exercise increase proteolysis, the process of protein breakdown. While BCAAs also act as an energy source during endurance exercise, more specifically, leucine oxidation increases with exercise performance (2). These two catabolic processes can elicit negative outcomes on performance.

BCAAs consumed in “free form” require minimal digestion and are rapidly absorbed into the blood stream; therefore, they can be taken up by muscles during exercise. It has been shown that the delivery of BCAAs + Arginine, such as those found in the Science in Sport BCAA Shot, to the working muscle can guard against the catabolic effects of exercise(3).

Moreover, as leucine is thought to be a key amino acid in triggering muscle protein synthesis(4). Maintaining muscle leucine concentrations, through exogenous BCAAs during exercise, could prime the system and support optimal recovery post-exercise; alongside adequate full amino acid provision.


When should I use the BCAA Shot?

Fasted training sessions have become a key part of an athletes training week, driving endurance adaptations and promoting optimal body composition. The main nutritional consideration behind these sessions is exercising with low levels of carbohydrate in the body – often achieved by training first thing in the morning, before breakfast. However, undertaking these fasted sessions with low carbohydrate availability can mean the body is more prone to using BCAAs for energy metabolism(5). Consuming a BCAA Shot before low carbohydrate training may help prevent this muscle breakdown. Research has also suggested that BCAA ingestion does not impair free fatty acid availability or fat oxidation during exercise in a carbohydrate restricted state, meaning the athlete can undertake these sessions while promoting muscle adaptations(6).

Given that prolonged and intense endurance exercise increases muscle protein breakdown and BCAAs are used to contribute towards energy production, it is useful to ingest a BCAA shot early on into long endurance sessions. In this way, muscle protein breakdown can be reduced during exercise, as a single intake of 2 g of BCAA with Arginine at the onset of exercise has been shown to supress the exercise-induced muscle protein breakdown(3). Additionally, BCAA supplementation with endurance training may also facilitate adaptations in aerobic power(7).


Take home messages

  • “Free form” BCAAs are absorbed rapidly into the blood-stream thus meaning they can be delivered to our muscles if taken pre or during exercise.
  • Supplementing with a BCAA Shot before low carbohydrate sessions may help reduce muscle breakdown while still promoting training adaptations.
  • BCAAs are used to contribute to energy production during endurance exercise. Consuming a BCAA Shot early on into long endurance sessions can therefore reduce muscle protein breakdown and support exercise performance.


  1. Kephart, W. C., Wachs, T. D., Mac Thompson, R., Mobley, C. B., Fox, C. D., McDonald, J. R., & Pascoe, D. D. (2016). Ten weeks of branched-chain amino acid supplementation improves select performance and immunological variables in trained cyclists. Amino Acids, 48(3), 779-789.
  2. Lamont, L. S., McCULLOUGH, A. J., & Kalhan, S. C. (2001). Relationship between leucine oxidation and oxygen consumption during steady-state exercise. Medicine & Science in Sports & Exercise33(2), 237-241.
  3. Matsumoto, K., Mizuno, M., Mizuno, T., Dilling-Hansen, B., Lahoz, A., Bertelsen, V., … & Doi, T. (2007). Branched-chain amino acids and arginine supplementation attenuates skeletal muscle proteolysis induced by moderate exercise in young individuals. International journal of sports medicine28(06), 531-538.
  4. Pasiakos, S. M., McClung, H. L., McClung, J. P., Margolis, L. M., Andersen, N. E., Cloutier, G. J., & Young, A. J. (2011). Leucine-enriched essential amino acid supplementation during moderate steady state exercise enhances postexercise muscle protein synthesis. The American Journal of Clinical Nutrition94(3), 809-818.
  5. Wagenmakers, A. J., Beckers, E. J., Brouns, F. R. E. D., Kuipers, H. A. R. M., Soeters, P. B., Van Der Vusse, G. J., & Saris, W. H. (1991). Carbohydrate supplementation, glycogen depletion, and amino acid metabolism during exercise. American Journal of Physiology-Endocrinology and Metabolism, 260(6), 883-890.
  6. Impey, S. G., Smith, D., Robinson, A. L., Owens, D. J., Bartlett, J. D., Smith, K., & Morton, J. P. (2015). Leucine-enriched protein feeding does not impair exercise-induced free fatty acid availability and lipid oxidation: beneficial implications for training in carbohydrate-restricted states. Amino Acids, 47(2), 407-416.
  7. Jafari, H., Ross, J. B., & Emhoff, C. A. W. (2016). Effects of Branched-Chain Amino Acid Supplementation on Exercise Performance and Recovery in Highly Endurance-Trained Athletes. The FASEB Journal, 30(1), 683





Ted Munson (Performance Nutritionist)
Written By

Ted Munson (Performance Nutritionist)

Ted is a Performance Nutritionist here at Science in Sport.