A resistance training exercise device, system and method having at least one elastic, elongated and hollow cord with a tether secured to each end of the cord, a strain relief sleeve and a clip secured to the free end of each tether, each tether being secured to their respective end of the cord by a grommet, plug and sleeve and each clip preferably comprising an o-ring that receives the free end of the tether and a spring-loaded biasing flange for clipping onto a handle, strap or the cord itself.