Since posterior means toward the backside, a posterior pelvic tilt is when your pelvis is tipped backward, causing your back to round. Think of your pelvis as a bowl tipping backward. This is actually the position that many people sit in on a regular basis. Being in this position for long periods of time can put a lot of stress on the discs in the back, and predispose you to a herniated disc.
Here, we are using it as part of an exercise to wake up your core muscles and improve your proprioception which is basically knowing where your joints are in space (as discussed in the Intro.)
Remember: We are going for improved proprioception in this exercise, so do all motions slowly and thoughtfully. Move with attention. Don't push into pain. Less is more here. Be really subtle, and notice everything. This will improve the connections to your brain. This exercise is even better on an exercise ball.
Posterior Pelvic Tilt
You might notice a lightness, or some relaxation in the muscles. Your breathing might get deeper. Your pain might decrease. Or you might not notice any difference yet. Keep going!
Great! Go to Part 4 - Anterior Pelvic Tilt