Bicycle Maneuver.

Lie with your lower back pressed into the floor and your hands clasped lightly behind your head. Bend your knees to about a 45-degree angle from the floor. Simultaneously, lift your shoulders off the floor, and bring your left knee to your right elbow, while straightening your right leg. Then using a bicycle-pedaling motion, straighten your left knee, while bringing the right knee in toward the left elbow. Extend your legs out only as far as is comfortable without arching your back. Continue alternating, keeping the movement slow and controlled.