Place your hands palms down facing the floor, hovering just above your belly button.
Quickly drive your right knee up to meet your right hand, then return it to the ground immediately, as you bring your left knee up to meet your left hand.
As you are alternating knees, you want to do it with a hopping motion, staying on the balls of your feet the entire time. Make sure you are engageing your abdominal muscles as well.
Repeat for 40 seconds, 50 seconds, or one minute, depending on the round you're on.