Drop Your Ribcage
Relax your ribcage down so that the front of the lower ribs line up vertically over the front outer edge of the pelvis (ASIS). The tendency to lift the chest up and thrust the lower ribs forward (also know as rotating your ribcage backwards) comes from multiple causes. One cause is a cultural teaching that "chest up" is good posture. Another cause is the chronic shortening of the Psoas muscle. However, learning to relax the ribs down will decrease the tension in your lower back, increase the stability of your core, and allow for a more stable torso for walking as your legs extend behind you.