Dietary Supplement. The Ultimate Underground Muscle Building Protein From the underground comes the meanest, most powerful, monstrous lean muscle generating protein to ever surface: Muscle Infusion Black. This daring formula is a unique blend of seven multi-functional protein fractions, each with a different absorption rate and a distinct sequence of highly anabolic amino acids. This powerful protein blend is fast-acting yet long-lasting. It triggers a quick anabolic onslaught followed by sustained muscle-building activities. Upon ingestion, its multi-layered protein fractions go straight to work. They continue to do so for several hours, feeding your muscles with highly anabolic and readily available amino acids.