Throwing and catching in sitting on exercise ball

Sit on an exercise ball with a partner standing in front of you holding a ball.
Your partner will start by gently throwing the ball towards you.
Catch the ball with both hands and throw it back to your partner from chest height.
To increase the difficulty of the exercise your partner should randomly, throw the ball at different heights, directions, and at different speeds.
You can progress this exercise by using a heavier ball.