While the current study strongly implicates faulty strand displacement replication as the causative agent of the muscular symptoms of aging and POLG-derived mitochondrial disease, a complete reckoning must await samples from other tissue types, from longitudinal collections from the same individual, from individuals with different environmental or pharmaceutical exposures or exercise regimes, and from patients with disparate disease phenotypes. The gene discussed is POLG; the disease is inborn mitochondrial metabolism disorder.