To make the repulsive elasticity of a bending part gentler than a coil spring alone by embedding the coil spring into a rubber member for connecting a pair of gripping parts and fitting the projecting parts of core materials projecting to the inner side ends of these gripping parts into the ends of the coil spring.

A pair of the left and the right slender bar-shaped gripping parts 3 are molded by an injection molding method of a resin and are formed as rough surfaces to facilitate the gripping of the surfaces of the gripping parts 3. Elasticity is otherwise imparted to the skin parts alone. A pair of the gripping parts 3 are connected by the rubber member 4 having a columnar shape and the coil spring 5 is embedded into the rubber member 4. Further, both ends of the coil spring 5 are fitted to the projecting parts of the core materials 6 consisting of metallic pipes which are fixed to the gripping parts 3 and are partly projected from the inner side ends of the gripping parts 3. The rubber member 4 and the coil spring 5 may be curved between the core materials 6 and the curving strength when both are mated is adjusted to the strength suitable for strengthening the muscular strength.