PEG-MGF is a derived form of the IGF-1 (insulin-like growth factor-1), which stimulates myoblasts division and allows for muscle fibers to fuse and mature. This is a process necessary for the growth of adult muscle. The distinction between IGF-1 and MGF is that MGF stimulates myoblasts division through the stimulation of different receptors. Research has demonstrated that PEG-MGF helps increase the muscle stem cell count, so that more may fuse and become part of adult muscle cells.