Definition of protein in nutritional science is a group of macronutrients in the form of amino acid compounds that function as substances builder and booster metabolism in the body. This substance cannot be produced by humans except through foods containing protein as well as supplements. You can go to View Website to see some examples of protein supplements for muscles.
So, protein is a major compound in the growth of new cells. After you do hard training, then the muscle becomes catabolic or burning muscle itself. This is where the consumption of protein foods is very important for muscle growth. This easy analogy, we analogy your muscles as a cube arrangement, when doing hard exercises the cube arrangement is starting to decrease one by one and protein is the main material forming the core of the cube. So muscle growth will be faster with additional protein enough as recovery after muscles get built up after a hard workout.