Prolab Nutrition Muscle Building StackThe Prolab Muscle Building Stack The Muscle Building Stack is one of the most important supplement stacks, especially if you work out every day, are an athlete, or bodybuilder. Rigorous training or competition will exhaust muscles and tear their fibers which will require necessary repair for growth. Without adequate support, muscles will remain stagnant or even suffer atrophy. Using a quality muscle building stack can help ensure sufficient recovery