Lie flat on the floor with lower back pressed to the ground; pull abs downward to target deep ab muscles. Interlace fingers and put hands behind head. Start by bringing knees in toward chest, lifting shoulder blades off the ground. Straighten right leg out to about a 45-degree angle from the ground while turning upper body to the left, bringing right elbow toward the left knee. Make sure rib cage is moving, not just elbows. Repeat on the other side. You should be creating a "pedaling" action; do this exercise with slow and controlled motion.