Breathing Mechanics and Lumbar Stability: A Missed Connection

The Diaphragm as a Postural Muscle

EMG studies demonstrate that the diaphragm activates in anticipation of limb movement, not in response to respiratory demand. It contracts to pressurise the abdominal cavity — a mechanism called intra-abdominal pressure (IAP) generation — which stiffens the lumbar spine via hydraulic and fascial pathways. When breathing pattern disorders reduce tidal diaphragmatic excursion, this postural preparatory function is compromised, and the global muscles are recruited as an inferior substitute.

Clinical Assessment

• Observe resting breathing pattern: chest-dominant vs. diaphragmatic
• Assess lateral costal expansion with hands on lower ribcage during relaxed breathing
• Perform the Niederauer IAP test: patient holds a Valsalva while therapist assesses abdominal wall stiffness
• Check for breath-holding strategy during functional movements (squat, deadlift, stair climb)

Retraining begins with 360-degree diaphragmatic breathing in supine before progressing through half-kneeling and standing tasks. The goal is integration: patients should generate adequate IAP through coordinated breathing, not conscious bracing, during all functional movements.