Branched-chain amino acids are essential amino acids (specifically, valine, leucine and isoleucine). "They are essential, meaning we must get them in our diet because our bodies do not produce them". The term 'branched-chain' just refer to the molecular structure. Amino Acids are the building blocks of protein (think: meat, dairy and legumes) and have various functions related to energy production during and after exercise so they are needed in adequate amounts, but not excessive. Increased Recovery - Perhaps the greatest benefit to hard training athletes is the increase in metabolic recovery that follows supplementation. Most athletes feel a substantial decrease in the amount of post exercise muscle soreness soon after beginning BCAA supplementation. Even without any of the other benefits of BCAA usage this means faster recovery from exercise induced protein damage (remember your muscles grow when you damage them), which in turn means faster size and strength gains. With increased recovery the harder and more frequently you can hit the iron and thus the sooner you can meet your goals. Endurance - The BCAAs can serve as a donor of nitrogen in the formation of l-alanine, which provides the body with glucose after glycogen stores have been depleted. When you think of sparing glycogen you probably think of high carbohydrate diets but BCAAs have proven their worth here as well. Stimulate Protein Synthesis - BCAAs by themselves have been shown to independently stimulate muscle protein synthesis. In other words, they have shown the ability to induce muscle gains, even in the absence of weight training.