Because free form amino acids don’t require digestion and are absorbed directly into the bloodstream as is, they are a much quicker and more efficient way to increase BCAA concentration in the body than eating whole protein. Research has shown that BCAA concentration in the blood elevates within 15 minutes and peaks 30 minutes after ingestion7, so supplementing with BCAAs starting about 15 minutes before training and then following your training session up with a good source of protein and carbohydrates is the general recommendation.