Rectus Abdominis

Origin, Insertion, Action, Innervation

Origin: Pubic crest and pubic symphysis
Insertion: Costal cartilages of ribs 5–7 and the xiphoid process
Action:
Primary: Flexion of the trunk (curling the thorax toward the pelvis)
Posterior pelvic tilt (pulls the anterior pelvis superiorly)
Compression of the abdominal contents (increases intra-abdominal pressure — supports the spine, assists forced expiration, and aids in defecation/urination/parturition)
Innervation: Thoracoabdominal nerves (ventral rami of T7–T12)

Palpation Guide

Client position: Supine with the knees flexed and feet flat on the table to relax the abdominal wall.
Landmark sequence:

Place your hand flat on the midline of the abdomen between the umbilicus and the xiphoid process. The rectus abdominis lies beneath the skin and subcutaneous fat, enclosed within the rectus sheath.
Ask the client to lift the head and shoulders slightly off the table (mini curl-up). The rectus abdominis contracts and its lateral borders become visible as two parallel vertical columns separated by the linea alba (midline).
Palpate the tendinous inscriptions — horizontal fibrous bands that divide the muscle into segments. These are typically visible in lean individuals and palpable as transverse ridges during contraction.
Trace inferiorly to the pubic attachment — the muscle narrows as it approaches the pubic crest.
The linea alba is the midline raphe between the two recti — palpable as a firm vertical line from the xiphoid to the pubic symphysis.

Tissue feel: When relaxed, the abdomen is soft and yielding (underlying viscera are palpable). When contracted, rectus abdominis feels like a firm, flat wall. The tendinous inscriptions feel like subtle transverse ridges within the contracted muscle.
Confirmation test: Ask the client to perform a mini curl-up (lift head and shoulders). The two parallel columns of rectus contract visibly. This distinguishes rectus from the obliques (which produce rotation, not pure flexion).
Common errors:
Confusing rectus abdominis with the external oblique — the oblique fibers run diagonally, not vertically. The lateral border of rectus (linea semilunaris) is the demarcation between rectus and the obliques.
Pressing too deeply through the abdominal wall — remember that the abdominal viscera (intestines, aorta) lie directly beneath the muscle layers. Deep palpation requires care and awareness of what lies beneath.

Trigger Point Referral

Common TrP locations: TrPs are found at multiple levels within the muscle, typically near the tendinous inscriptions. Common sites include the periumbilical region and the area between the umbilicus and the xiphoid process.
Referral pattern: Refers in horizontal bands across the abdomen at the level of the TrP, and can refer to the mid and low back — producing a "belt-like" pain pattern. TrPs near the lower attachment can refer to the lower abdomen and pelvic region.
Clinical significance: The back pain referral from rectus abdominis TrPs is frequently mistaken for spinal pathology. If a client has mid-back or low-back pain that worsens with sit-ups or trunk flexion but has no spinal findings, check the rectus abdominis for TrPs.

Trigger point referral diagram — coming soon

Image coming soon. For visual reference, see [Rectus Abdominis at TriggerPoints.net](http://www.triggerpoints.net/muscle/rectus-abdominis).

Clinical Notes

Common conditions:

Key muscle in conditions/lower-crossed-syndrome — rectus abdominis is part of the "weak" group (along with the gluteals) that becomes inhibited as the hip flexors and erector spinae shorten. Weakness of rectus allows the pelvis to tilt anteriorly, increasing lumbar lordosis. Strengthening rectus abdominis (along with the other abdominals) is a cornerstone of lower crossed syndrome rehabilitation.
Diastasis recti — separation of the two rectus abdominis columns at the linea alba, most commonly occurring during and after pregnancy. Palpated as a gap greater than 2 finger-widths at the linea alba during a curl-up. Clients with diastasis recti should avoid full sit-ups and crunches until the separation has resolved — refer for specialized rehabilitation.
Involved in chronic conditions/low-back-pain through anterior stabilization failure — weak or inhibited rectus abdominis reduces the ability to generate intra-abdominal pressure, which is a key spinal stabilization mechanism.

What you'll typically find:

In clients with low back pain, the rectus abdominis is often weak and inhibited (consistent with lower crossed syndrome) but may simultaneously harbor TrPs that refer pain to the back. The muscle can be both weak (globally inhibited) and locally hypertonic (TrP taut bands) at the same time.
Post-surgical clients (abdominal surgeries including cesarean section) often have scar tissue adhesions in the rectus sheath that restrict trunk flexion and contribute to altered movement patterns.

Treatment effects:

TrP release in rectus abdominis can produce immediate reduction in referred back pain. Use gentle sustained compression — the abdominal wall is thin and the viscera are immediately beneath.
Myofascial release of the rectus sheath and linea alba can improve trunk flexibility and reduce the "pulling" sensation that some clients report in the anterior abdomen.
Post-surgical scar mobilization along the linea alba and any incision lines (wait at least 6–8 weeks post-surgery) can restore tissue mobility.

Cautions:

The abdominal aorta lies on the posterior abdominal wall, palpable as a pulsation in the midline deep to the abdominal muscles, especially in thin individuals. Be aware of aortic pulsation — an abnormally wide, pulsatile mass in the midline may indicate abdominal aortic aneurysm. Refer immediately.
Avoid deep abdominal work during pregnancy — increased intra-abdominal pressure and deep compression can be harmful. Light, superficial techniques only.
Visceral referral — tenderness in the lower abdomen can arise from appendicitis (right lower quadrant), diverticulitis (left lower quadrant), or other visceral pathology. If abdominal tenderness is accompanied by fever, rigidity (involuntary guarding), or rebound tenderness, refer for medical evaluation.

Postural significance:

Rectus abdominis is part of Janda's "weak" group in lower crossed syndrome. When inhibited, it fails to counteract the anterior pelvic pull of the hip flexors, resulting in excessive lumbar lordosis. Strengthening the abdominal wall (not just rectus but all four abdominal muscles) is essential for restoring pelvic neutral and reducing posterior lumbar loading.

Clinical pearl:

Check for diastasis recti in every postpartum client and any client with a protruding abdomen who reports low back pain. Have the client perform a slow curl-up while you palpate the linea alba at the umbilicus level. A gap of more than 2 finger-widths suggests diastasis. This finding changes the exercise prescription — traditional crunches and sit-ups are contraindicated until the separation narrows.

Assessment

Manual muscle testing:

Trunk flexion (curl-up): Client supine with knees flexed. Ask the client to curl the trunk, lifting the scapulae off the table. Arms crossed over the chest increases difficulty. Grade by how far the client can curl and against what resistance.

Stretch test:

Trunk extension: Client prone. Support into gentle trunk extension (press-up position). Resistance or pulling in the anterior abdomen suggests rectus abdominis shortening. Compare to baseline.

Related special orthopedic tests:

Diastasis recti palpation test — palpate the linea alba during curl-up; gap > 2 finger-widths is positive
Thomas test — hip flexor tightness assessment (part of the lower crossed syndrome evaluation alongside rectus abdominis weakness testing)

Muscle Groups

Anterior abdominal wall (anatomical):

Trunk flexors (functional):

Rectus abdominis (this article)
anatomy/muscles/external-oblique (bilateral)
anatomy/muscles/internal-oblique (bilateral)

Lower crossed syndrome — "weak" group (clinical):

Rectus abdominis (this article)
anatomy/muscles/external-oblique
anatomy/muscles/internal-oblique
anatomy/muscles/transversus-abdominis
Gluteus maximus
Gluteus medius

Related Muscles

Synergists for trunk flexion:

anatomy/muscles/external-oblique — flexes trunk when contracting bilaterally; adds rotation when unilateral
anatomy/muscles/internal-oblique — flexes trunk when contracting bilaterally; adds rotation when unilateral

Antagonists:

anatomy/muscles/erector-spinae-iliocostalis — trunk extension
anatomy/muscles/erector-spinae-longissimus — trunk extension
anatomy/muscles/erector-spinae-spinalis — trunk extension
anatomy/muscles/multifidus — segmental extension and stabilization

Functional partners (intra-abdominal pressure):

anatomy/muscles/transversus-abdominis — primary generator of intra-abdominal pressure
anatomy/muscles/diaphragm — generates pressure from above
Pelvic floor muscles — generate pressure from below

Key Takeaways

Rectus abdominis TrPs refer pain to the back in horizontal bands — check the abdominal wall in any back pain presentation that does not correlate with spinal findings.
Part of the "weak" group in lower crossed syndrome — weakness allows anterior pelvic tilt and excessive lumbar lordosis.
Always screen for diastasis recti in postpartum clients and anyone with a protruding abdomen — a gap > 2 finger-widths at the linea alba changes the exercise prescription.