Before understanding what amino acids build muscle, you first need to know the role of amino acids in your body. Amino acids are what creates new tissue in your body. When you exercise your muscles, you are essentially breaking down your muscle tissue (catabolism). Following muscle breakdown is the process of repairing, and growth of the muscle (anabolism). Therefore, you need a sufficient amount to build muscle to carry out this process efficiently. In order for the muscle to grow, your body needs to consume more synthesized proteins than it is consuming through catabolism.
There are 23 amino acids that make up a protein. They can be divided up into two groups: essential amino acids, and non-essential amino acids.
There are 9 essential amino acids. These come from the foods we eat. The 12 non essential amino acids are derived from other the other amino acids in your body. All 23 amino acids need to be present in order for protein synthesis to occur.
It has been found that carbohydrates consumed after workouts is effective in delivering glycogen to your muscle tissue faster. Carbohydrates taken in combination with protein has been found to stimulate protein synthesis. This is why it is recommended by so many in the sports science community.After you complete a workout, blood flow is increased in the muscles which have been broken down. These creates a window of opportunity to ingest amino acids. Drinking a protein supplement or having a high protein meal in combination with carbohydrates after your workout is effective. Some people opt to take a BCAA supplement since they are under the impression that it still can take a couple of hours for that protein to break down in the form of amino acids. This is one reason why many bodybuilders consume free form amino acid supplements during and following their workout. These free form amino acids have already been broken down. Therefore, there is no time wasted with digestion and they are ready to enter the blood stream very quickly.
There is also another reason why many choose to take amino acid supplementation. When your muscles are under heavy load from working out, Branched Chained Amino Acids (BCAAs) are taken from your muscles for energy (muscle is being broke down). People choose BCAA supplements in order to prevent break down of the muscle. Extra BCAAs will be used for energy instead of BCAAs from your muscles if available (see study: http://jap.physiology.org/content/74/6/2711.abstract)
But Are These BCAA Supplements Really Necessary?
For those who are not getting adequate high quality protein, sure. However, let’s not forget that protein sources from animals, whey protein, and others already have BCAAs. As long as you are getting adequate protein from these sources, BCAA supplements are unnecessary because the BCAAs already exist in your bloodstream. There has yet to be a study showing the benefits of BCAA supplements over BCAAs derived from other food sources. So if you want to avoid spending money on BCAA supplements, increase your protein intake and you will be fine.