Your body requires a variety of vitamins, minerals, and micronutrients to build new muscle after you work out. Protein shakes are a great option for rebuilding muscle fibers after a workout.Testomenix You simply cannot build muscle effectively without getting on the right diet. Without proper nutrition, it will be difficult for your body to regenerate muscle fibers. Protein is one of these nutrients, and consuming a protein shake after a workout will promote muscle repair and growth.Testomenix Have between 20 to 30 grams of protein in each meal in order to make sure you have enough protein.