• Begin standing with your feet shoulder-width apart, holding a 15-pound med ball in front of your chest.
• Perform a three-quarter squat, bringing the med ball down between your legs.
• Explosively jump as high as possible, fully extending your arms above your head, like you’re trying to dunk a basketball.
• Land in the start position, and repeat.
  

Make sure you keep your back flat, and load your glutes and hips in the squat position. Keep your eyes on the med ball throughout the entire movement. During the season, I usually superset these with a rotational or back exercise, performing two sets of 10 to 15 reps.