Muscles do not grow while you are training but in the time between your workout sessions - training is just the growth stimulus. In addition to sufficient amounts of protein and a generally nutrient-rich diet, our sleep is extremely important too. While you are asleep, your muscles have the chance to fully recover from the intense exercise. Pro tip: Supply your muscles with high-quality protein overnight. The milk protein casein, which is the main ingredient in our delicious Protein 80 Plus, is slowly digestible and supplies the body with important amino acids for up to seven hours - perfect before going to bed!