Protein - What is it good for? Protein is basically the building block for muscle repair and growth. When you're training, especially with weights or resistance, you're creating tiny tears in your muscle fibers, and protein helps repair those tears, making the muscles stronger and bigger over time. So it's really essential for recovery, for building lean muscle mass, and overall for just keeping your body fueled for the next workout. The Bulk Protein Company, SERIOUS GAINZ - Whey Protein Powder