Considering the limited knowledge about expression levels of AMPK, AMPK-related genes, and FAPs associated with growth-related myopathies in chickens, the aim of this study was to evaluate the absolute expression of those genes in P. major muscle during post-hatch muscle development (from 7 to 42 days of age) in fast-growing (FG) and medium-growing (MG) chickens. The gene discussed is PRKAA2; the disease is myopathy.