1. Stand with one foot flat on a box, the other on the floor behind you, and your arms back with elbows bent to 90 degrees.
2. Jump vertically by swinging your arms forward and exploding through your front hip, knee, and ankle.
3. Switch legs in mid air so you land with the opposite foot on the box.
4. Without pausing, immediately repeat the movement, exploding back up with your opposite leg.
5. Continue alternating to complete the set.
Be sure to: Minimize contact time. That is, anticipate landing with a slight forward lean in your torso, your back leg bent slightly, and your full foot on the box.
You should feel it: Working your hips and legs.