| 摘要 |
A training and coordination device including a projectile member such as a ball or sack secured to an elastic string is described. The first end of the elastic string is attached to a location and the second end is connected to the projectile member. At least an end portion of the elastic string secure to the projectile member comprises multiple strands of an odd number. The multiple strands of the elastic string in conjunction with the elasticity of the string generate a random motion of the sack when the sack moves relative to the string. |
