Doing windshield wipers lying down will build the rotational core strength you need as a foundation. Lie on your back on the floor and raise your legs 90 degrees. Spread your arms straight out to your sides for support. Rotate your legs to one side, stopping short of touching the floor.

Lie on the floor with your hands lightly placed on either side of your head. Press your lower back into the ground. Lift your knees to a 45-degree angle. Bring your right knee toward your chest, as if it was on the upward swing of pedaling a bike. At the same time, bring your left elbow toward the knee. Repeat on both sides.