The article identifies cellular survivorship bias as a major mechanism of muscle stem cell (MuSC) aging. During aging, MuSCs with damaged mitochondria survive preferentially, which leads to a loss of oxidative phosphorylation (OXPHOS) and a reduction in muscle regeneration capacity. This bias explains the decrease in the number of MuSCs, loss of quiescence and increased senescence, characterized by irreversible cell cycle arrest and the senescent secretory phenotype (SASP). Study shows that genetic restoration of OXPHOS or mitophagy in senescent MuSCs improves muscle regeneration. Epigenetic derepression of p16 and p21 genes in old MuSCs promotes their transition to senescence. Increasing the MuSC pool by approximately 50% is not sufficient to slow sarcopenia or muscle loss.