Branched-chain amino acids (BCAAs) are a group of three essential amino acids valine, leucine, and isoleucine. Essential amino acids, especially BCAAs, play an important role in regulating muscle protein metabolism (Valenzuela 2019). BCAAs are abundant in skeletal muscle and may help increase muscle protein synthesis and prevent muscle protein breakdown (Rahimi 2017). Supplementation with BCAAs is a nutritional strategy thought to avoid or at least lessen muscle damage caused by exercise (Fouré 2017). Exercise-induced muscle damage leads to a loss of muscle strength and power; therefore, reducing the damage may be of interest to elite athletes to improve subsequent performance following intense training (Rahimi 2017).
Supplementing with BCAAs provides an anabolic stimulus both during exercise and in resting conditions (Valenzuela 2019). This may alleviate the consequences of exercise-induced muscle damage. BCAAs can also improve physical markers of fatigue and muscle soreness (Hormoznejad 2019).
BCAAs, particularly leucine, serve to induce muscle protein synthesis and limit protein breakdown. Leucine is a signaling molecule that activates the mTOR pathway leading to muscle protein synthesis (Fouré 2017). It has proven to be the most effective at stimulating anabolic processes. However, its effects on muscle mass are controversial as there is no muscle strength benefits provided (Valenzuela 2019).
The evidence for supplementing with BCAAs to reduce or prevent muscle damage from intense exercise is poor since there is no direct evidence of positive effects of BCAAs on muscle damage (Fouré 2017). Research evaluating effects on muscle soreness following intense exercise reports that BCAAs did not alleviate symptoms of delayed-onset muscle soreness at 24, 48, 72, and 96 hours following exercise (Rahimi 2017).
BCAA supplementation does not appear to have a significant effect on feelings of fatigue, but it does have a positive effect on fatigue substances, which could lead to favorable effects on muscle damage substances and energy metabolites (Hormoznejad 2019).
Supplementing BCAAs is safe when the levels are in a ratio of 2:1:1 for leucine, isoleucine, and valine, since supplementing only leucine may cause a BCAA imbalance (Valenzuela 2019). Practical recommendations for BCAA supplementation cannot be made due to variability in both dosing strategies and characteristics of muscle damage. In general, the findings for reducing muscle damage and subsequently improving performance are inconsistent. (Rahimi 2017)
Fouré A, Bendahan D (2017). Is branched-chain amino acids supplementation an efficient nutritional strategy to alleviate skeletal muscle damage? A systematic review. Nutrients, 9(10), 1047.
Hormoznejad R, Zare Javid A, Mansoori A (2019). Effect of BCAA supplementation on central fatigue, energy metabolism substrate and muscle damage to the exercise: A systematic review with meta-analysis. Sport Sciences for Health, 15. 1-15.
Rahimi MH, Shab-Bidar S, Mollahosseini M, Djafarian K (2017). Branched chain amino acid supplementation and exercise induced muscle damage in exercise recovery: A meta-analysis of randomized clinical trials. Nutrition, 42, 30-36.
Valenzuela PL, Morales JS, Emanuele E, Pareja-Galeano H, Lucia A (2019). Supplements with purported effects on muscle mass and strength. European Journal of Nutrition, 58, 1-26.