• Origin

Sternal Part: Posterior surface of the xiphoid process.

Costal Part: Internal surfaces of the lower six ribs and their costal cartilages (ribs 7–12).

Lumbar Part:
• Right and left crura from the anterolateral surfaces of the upper lumbar vertebrae (L1–L3).
• Medial and lateral arcuate ligaments.

• Insertion

Central tendon of the diaphragm

• Agonist(s)

- External intercostals (assist in inspiration),

- Scalene muscles (assist in lifting the upper ribs during deep inspiration),

- Sternocleidomastoid (in forced inspiration).

• Antagonist(s)

- Internal intercostals (assist in forced expiration),

- Abdominals (particularly rectus abdominis and transversus abdominis during forced expiration).

• Function

Primary muscle of respiration.

Contracts during inhalation to increase thoracic volume and decrease pressure, allowing lungs to expand.

Assists in increasing intra-abdominal pressure (e.g., during coughing, vomiting, defecation, childbirth).

Plays a role in maintaining thoracoabdominal pressure balance.

TRIGGER POINT(S)

• Location

Trigger points may develop in the muscular periphery near the costal margins, especially where the diaphragm inserts on the lower ribs and the crura attach to the lumbar vertebrae.

• Pain Referral Pattern

Referred pain may mimic chest pain or discomfort in the lower ribs.

May radiate to the mid-thoracic spine or upper abdominal region.

Can mimic symptoms of heartburn or gastrointestinal discomfort.

Tightness or restriction may lead to a sensation of restricted breathing or fullness in the chest.

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Potential Causes

• Chronic stress and anxiety (causing shallow, chest-dominant breathing).

• Prolonged poor posture, especially slouched or kyphotic positions.

• Shallow or paradoxical breathing patterns.

• Respiratory illnesses such as asthma, bronchitis, or chronic obstructive pulmonary disease (COPD).

• Surgical scarring or abdominal adhesions impacting diaphragm mobility.

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Prevention Tips

• Practice diaphragmatic (belly) breathing techniques to enhance function and relaxation.

• Maintain good postural alignment to allow full expansion of the diaphragm.

• Manage stress through breathwork, mindfulness, or relaxation techniques.

• Stretch the thoracic spine and rib cage to improve mobility.

• Engage in regular cardiovascular exercise to promote full-range breathing.

• Treat and address scar tissue or fascial restrictions following abdominal or thoracic surgery.