A resilient element having an elongated body of an elastic material through which a rope of a corresponding elongated and flexible tension element winds undulating, wherein a spring force being generated by the body at stretching of said undulation when applying a tension force in the tension element. The body having at least one S-shaped portion with at least three essentially traverse legs, in which two adjacent legs alternately are joined with each other at one side of the elongated the body and having an opening at the other side of the elongated body, wherein the tension element is intended to be introduced through said opening and undulates alternately over and below, respectively, adjacent legs.