First, let's start with the basics. Why is it so important to use a protein powder post-workout? When you work out, consuming adequate protein is critical to increasing overall muscle protein synthesis. When you engage in strenuous activity, your muscles first break down, which engages a response from your body to begin repairing the muscle fibers and increasing the strength of the tissue. To properly repair the damaged muscle fibers, you need sufficient protein. But, not all protein is created equal.