Dear sir, why sportmen use amino acids and how can i know that i'm at lack of amino acids ???

Amino acids come: from protein. Sportsmen drink protein shakes which have 30g protein per serving. But protein supplements are very expensive. You can get the SAME amino acids from normal food sources in dairy, eggs, fish, meat or tofu form. It tends to be MUCH cheaper than protein shakes, ounce for ounce! You should eat approximately 3000 calories per day, 25% coming from protein.

Amino acids are the : building blocks of proteins. We all need to have minimum amount of proteins per day to repair muscle, to restore neurotransmitters, and to just do the activities of daily living. If you're an elite athlete, you definitely need to replenish your proteins, as well as your carbohydrates. So often the amino acids can come formulation with collagen peptide to also repair got, help hair, skin & nails.