The Abdominal muscles what people think of as your six pack muscles. They are mostly responsible for flexing the spine and postural stability. These muscles are often tight in people with poor posture with a rounded spine. This causes trigger points to developed. Trigger points in the abs cause pain to be felt in the abdomen, but also frequently in the back. Trigger points in the upper abdominals refer pain into the mid back, and points in the lower abdominals produce lower back pain.