Starting Position: Make sure that you are working with a partner who can catch the ball. Let the partner feel the medicine ball first so the partner knows how much it weighs and can prepare to catch it. Position your body directly facing your partner with the feet hip-width apart, the left foot slightly forward and the right foot slightly back, heels on the floor. The spine is in neutral (normal-to-flat), shoulder blades pulling down your back. Your chest is lifted and your head is in line with your spine. Contract and brace the abdominals. Hold the medicine ball with both hands. Your eyes should be looking directly at the target in order to properly aim the throw.
Swing your arms upward to bring the medicine ball overhead, bending your elbows to reach the medicine ball behind your head. Your feet are pressed into the ground, and abdominal muscles braced. As you lift the ball over your head, shift your weight back into your right leg and lean back, engaging the core muscles for extra power in the throw. While preparing to release the ball aim the throw by keeping your eyes on your partner's hands as you pull the ball back over your head.
Explosively step forward with the right leg, push the left leg into the ground to fully extend the ankles, hips and knees to generate momentum, as you bring your arms forward over your head to generate power for throwing the ball.
Exercise Variation: Repeating throws: Use a wall with a medicine ball capable of bouncing and position yourself so that you can throw the ball into the wall and quickly catch it to prepare for the next throw.
The purpose of this exercise is to generate upper body power, use a ball that is no more than 10% of your bodyweight to ensure that you can achieve the appropriate velocity for the throw.