1. Lie on your back with the knees bent and the soles of the feet on the floor. This is your neutral position, with the natural curve of the lumbar spine causing the low back to be slightly elevated from the floor.
2. On an exhale, gently rock your hips towards your face. Your butt will not actually leave the floor, but you will feel your low back press into the floor. You are essentially taking the curve out of the low back.
Think of the pelvis as a bowl of water. When you do the pelvic tilt, the water would be spilling towards your belly.
3. After a few seconds, inhale and return to your neutral position.
4. Repeat this movement 5 to 10 times.
The animation above illustrates the subtlety of the movement.