An extensible chain includes a plurality of cage-shaped elements (2) connected to one another in succession, each one of which includes a flat central body (3) from which two or more lateral arms (4) branch off whose free ends are slidingly inserted in an adjacent cage-shaped element. The adjacent elements define an intermediate space in which there is a spring (6) obtained from a plane metal sheet element from which two tabs (6b) depart that are opposite each other with respect to the base of the metal sheet element and are positioned above it at a distance (H) that, when the spring is at rest, exceeds the distance between the free ends of the lateral arms (4) of any cage-shaped element and the central body (3) of the adjacent cage-shaped element.