Leucine, isoleucine and valine are called branched-chain amino acids (BCAAs.) They are essential amino acids, which means they must be consumed in the diet. BCAA’s are involved in protein synthesis, tissue repair, signaling a biochemical pathway essential for muscle protein synthesis (i.e. mTOR) and blood sugar control. A meta-analysis that combined the results of seven studies showed that BCAA supplements are best taken after exercise, not before, or during exercise (intra-workout.) The studies revealed that BCAA taken during exercise, “is not effective on muscle soreness at follow-up time, ” the researchers wrote.
Leucine consumption before your workout promotes sluggishness and fatigue. Recent research has shown that leucine competitively inhibits dopamine precursor tyrosine into the brain, and reduces dopamine levels. Dopamine and noradrenaline are the “flight or fight” hormones that allow the body to perform at higher levels than normal. Increasing dopamine reduces fatigue and increases mental arousal, focus, confidence and greater levels of motivation! Pre-workout leucine and BCAA consumption is not the best for optimal muscular performance!
According to the meta-analysis, when BCAA’s are taken after exercise, they reduce post-exercise muscle soreness and creatine kinase – a marker of muscle damage – better than rest alone.
BCAA’s promote recovery by stimulating the mTOR pathway to increase protein synthesis to repair injured tissue. Leucine, one of the BCAAs, is the most important chemical that turns on the mTOR pathway, so it is likely that consuming leucine after exercise would be just as effective or more effective (and cheaper) than consuming BCAA’s. The addition of isoleucine and valine may hinder the benefits of leucine due to competition for transport into muscle cells. The BCAA’s share the same active transport system into cells and muscle cells. (Nutrition, 42: 30-36, 2017.)