USE A NON-BOUNCING MED BALL!
Start seated with the med ball at your chest. Jump and extend straight up as high as you can. On he way down start to pul the balm down and slam it into the ground as hard as you can.
These were typically done on our upper body days. Start with 3x5 and increase the volume weekly to as many as 8x5 over the course of a few weeks.