The exercise below effective trains the abdominal muscles by throwing the volley ball overarm.
Lie down on the floor with bent knees.
Hold the ball with two hands, and bring your arms stretched behind your head as far as possible. This is also the start position of the exercise.
Get up evenly, with both your arms and your upper body, to throw the ball as far as possible. It is important to maximize tension of your abdominal muscles.
You can repeat this exercise 8 to 16 times, in 1 to 3 sets.