Begin with your hands and knees on the floor. Make sure your knees are under your hips and your wrists under your shoulders. Begin in a neutral spine position, with your back flat and your abs engaged. Take a big deep inhale.
On the exhale, round your spine up toward the ceiling, pulling your belly button up toward your spine. Tuck your chin toward your chest, and let your neck release.
Stay like this for a few breaths; you can also "wag" your tailbone gently from side to side.