L-Arginine is a conditionally essential amino acid. This means that our bodies synthesize it in sufficient quantities, but in extreme conditions (during workouts) the quantities are insufficient. One of the main effects of the increased levels of L-Arginine in the organism is the widening of blood vessels. Thus is increased the blood flow, respectively the flow of oxygen and nutrients to the muscle cells, which stimulates muscle growth. This effect is achieved only when the amount of L-Arginine in the body is higher than usual. L-Arginine received in appropriate quantities and in the appropriate time increases the level of somatropin (growth hormone) in the organism. Thus stimulates the muscle protein synthesis, therefore increases recovery and growth of muscle cells. Foods, such as peanuts and almonds, are natural sources of L-Arginine, but the easiest way to supply the body with enough quantity is through supplementation. It is recommended for muscle building programs.