For athletes, L-arginine is a very attractive amino acid as it has two interesting aspects. First, Although L-arginine is an amino acid that the body can produce from L-glycine and L-methionine itself, this may not be sufficient in times of intense exercise, during a diet or in stressful situations. Therefore, it is important to offer your body this semi-essential amino acid to support your protein metabolism. Secondly, L-arginine is the only precursor of nitric oxide (NO), a bioactive molecule that causes the effect of widening the veins. This leads to increased blood flow to the muscles and this means increased transport of oxygen and nutrients. And you need this especially in the sporty stress phase.