The rectus abdominis is you “six pack” muscle. It originates on the pubic bone and inserts on the costal cartilage of ribs 5-7, and the xiphoid process of the sternum. It’s main actions are to flex and rotate the spine, as well as increase the intra-abdominal pressure. Trigger points in this muscle refer pain into the mid and lower back. This muscle is tight in people who slouch and have a posteriorly rotated pelvis. An anteriorly rotated pelvis can be corrected by strengthening this muscle.