"Flexibility” is a physical quality of a person, which is characterized by the ability to perform movements with a large amplitude. Flexibility is important for success in such activities as sports (artistic and rhythmic gymnastics, figure skating, etc.), as well in classical choreography, for example, ballet. Extracellular matrix producing cells and structural proteins of connective tissues take an active part in the formation of mobility of the elements of the musculoskeletal system. Connective tissues are a complex structural and functional system, the components of which are encoded by many genes. Mutations in them lead to various hereditary diseases that increase or decrease "flexibility”. The role of genes in the formation of conditions encoded in the ICD-11 LD28.Z remains unclear - "Syndromes involving connective tissue as the main feature, unspecified”, and their prognostic significance for people experiencing intense physical exertion. The purpose of this review is to generalize modern ideas about the role of genes, extracellular matrix and cells producing it in the formation of such a physical quality as flexibility.