Lie on your back with your legs together and your hands behind your head. Tuck your tailbone and make sure your back is completely flat against the floor.
Lift both legs a few inches off the floor, making sure to keep your lower back flat and core braced.
Bend your left leg and bring it toward your chest slowly and with control. Rotate your torso slightly to bring your right elbow near your left knee, making sure not to pull on your neck as you do; the movement should initiate from your torso, not your neck or arm.
Straighten your left leg while simultaneously bending your right leg toward your chest. Repeat the movement on the other side, crunching your left elbow toward your right knee.