As jumping is an effective method of moving over rough terrain, there is much interest in building robots that can jump, and deformation of a soft robot's body is an effective method to induce jumping. Our aim was to investigate the effect of the initial shape of deformation of a circular shell made of spring metal. Four initial shapes of deformation: dish, peanut, cup and cap, jumped the highest in that order, with the dish jumping twice as high as the cap. A simulation of a model was in good agreement with the observations.