Gymnasts sprint down a runway, which is a maximum of 25 meters in length, before hurdling onto a spring board. The gymnast is allowed to choose where they start on the runway. The body position is maintained while "punching" (blocking using only a shoulder movement) the vaulting platform. The gymnast then rotates to a standing position. In advanced gymnastics, multiple twists and somersaults may be added before landing. Successful vaults depend on the speed of the run, the length of the hurdle, the power the gymnast generates from the legs and shoulder girdle, the kinesthetic awareness in the air, and the speed of rotation in the case of more difficult and complex vaults.