More recently, the double KO of ERRα and ERRγ in mice was shown to lead to dramatic changes in muscle physiology, with a severe reduction in gene expression related to mitochondrial oxidative metabolism (and consequently energy production), histological abnormalities reminiscent of congenital myopathies, and marked exercise intolerance [79,80]. The gene discussed is ESRRA; the disease is congenital myopathy with cores.