The functions of the abdominal muscles are to increase the intra-abdominal pressure to support the spine, and to flex and rotate the spine. The rectus abdominis has vertical fibers and is a spine flexor. The internal and external obliques can also rotate the spine as well as flex it.
Regarding back pain, the rectus abdominis is known to refer pain in a horizontal band across the back, at the same level the as the trigger point. Any of the muscle inscriptions could harbor TrPs. Thus low back pain, horizontally across the sacrum can be the result of TrPs in the lowest inscription of the rectus abdominis. The obliques tend to refer pain in their local area and also spreading up and around the abdominal area and also downward into the groin area. The obliques don't directly refer into the back but may satellite into the rectus abdominis and into the back. Also of note, the abdominal muscles can refer into the internal organs which are smooth muscle and can cause internal organ dysfunction and pain. This is often overlooked in diagnoses of organ disease.
Trigger points and dysfunction in the abdominal wall muscles is associated with dysfunctional breathing. If the person is not breathing diaphragmatically, the abdominal wall muscles are not be expanding and contracting and will tend to harden. This will then prevent diaphragmatic breathing. Also, overzealous abdominal exercising can create hardness in these muscles which will then produce pain and discourage diaphragmatic breathing.
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