The activation and proliferation of satellite cells contribute to the long-term potential for muscle hypertrophy and repair.

While the primary mechanism of muscle hypertrophy is the enlargement of existing muscle fibers, satellite cells play a crucial role, particularly in significant or sustained growth, and in muscle repair. Satellite cells are quiescent stem cells located beneath the basal lamina of muscle fibers. In response to muscle damage or intense training, these cells become activated, proliferate, and then fuse with existing muscle fibers. This fusion process donates new nuclei to the muscle fibers. Since muscle cells are multinucleated, adding more nuclei (myonuclei) helps maintain a sufficient 'myonuclear domain' – the cytoplasmic volume controlled by a single nucleus. This is important because each nucleus is responsible for regulating protein synthesis within its domain. Therefore, an increased number of myonuclei supports the greater protein synthesis required for substantial and sustained hypertrophy, as well as aids in the repair of damaged fibers.