This exercise is similar to the motions of bowling.
Steps
Hold a Medicine Ball in one hand with your palms facing up at shoulder height. Bring one foot back and into a lunge, keeping your front foot stationary and not letting your back knee touch the ground.
While lunging bring the ball down and back as if you were bowling. Bring your arm back up to the starting position, switch legs and repeat.
Tips
Use slow and steady movements with this exercies.