Done in (slow) cadence ... Starting position: Lie on your back, legs & arms extended out in an "X" position ... on the 1-count, simultaneously lift your left leg and right arm together to meet above your core, trying to keep both straight as possible as you touch your right arm to your left leg and then returning to the starting "X" position ... on 2-count, flap-jack with your right leg and left arm, again trying to keep both straight as possible as you touch your left arm to your right leg above your core and before returning to the starting "X" position ... on 3-count, execute a knee-up, lifting your shoulders and legs off the ground and touching your toes as you bring your knees up with just your six touching the ground ... on 4-count, extend arms and legs and return back to the starting "X" position. That is one rep.