It is well known that exercise training enhances the expression of a subset of genes involved in skeletal muscle phenotypic adaptation.However,the exact molecular mechanisms are not yet fully understood.Given the important role that myocyte-specific enhancer factor 2 (MEF2) plays in myoblast differentiation and muscle-fiber shifting,it seems clear that many of these genes expressed in muscle are regulated by MEF2.Muscle-type carnitine palmitoyltransferase 1 (CPT1b),which controls mitochondrial fatty acid β-oxidation in skeletal muscle,has been viewed as one of the key regulators in modulating metabolic adaptation in response to exercise training.