How does concertina locomotion help a caecilian burrow underground?

Caecilians utilize concertina locomotion to navigate through soil by alternately folding and extending their bodies along their entire length. This process can occur through flexures of the entire body or within the envelope of skin that encases their muscular frame.1

This movement is facilitated by a specialized axial musculoskeletal system. The caecilian's skin is attached to the axial muscles by fibrous connective tissue, creating a tough, outer muscular sheath that is largely disconnected from the vertebral musculature. This unique arrangement allows the skin and superficial muscles to move as a single unit, independent of the internal skeleton, which provides the necessary leverage and flexibility to tunnel effectively through subterranean environments.12