Postural function of the diaphragm in persons with and without chronic low back pain.

STUDY DESIGN A case-control study. OBJECTIVES To examine the function of the diaphragm during postural limb activities in patients with chronic low back pain and healthy controls. BACKGROUND Abnormal stabilizing function of the diaphragm may be an etiological factor in spinal disorders. However, a study designed specifically to test the dynamics of the diaphragm in chronic spinal disorders is lacking. METHODS Eighteen patients with chronic low back pain due to chronic overloading, as ascertained via clinical assessment and magnetic resonance imaging, and 29 healthy subjects were examined. Both groups presented with normal pulmonary function test results. A dynamic magnetic resonance imaging system and specialized spirometric readings were used with subjects in the supine position. Measurements during tidal breathing (TB) and isometric flexion of the upper and lower extremities against external resistance with TB were performed. Standard pulmonary function tests, including respiratory muscle drive (PI(max) and PE(max)), were also assessed. RESULTS Using multivariate analysis of covariance, smaller diaphragm excursions and higher diaphragm position were found in the patient group (P<.05) during the upper extremity TB and lower extremity TB conditions. Maximum changes were found in costal and middle points of the diaphragm. A 1-way analysis of covariance showed a steeper slope in the middle-posterior diaphragm in the patient group both in the upper extremity TB and lower extremity TB conditions (P<.05). CONCLUSION Patients with chronic low back pain appear to have both abnormal position and a steeper slope of the diaphragm, which may contribute to the etiology of the disorder.