Postural Function of the Diaphragm in Persons With and Without Chronic Low Back Pain
??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.
1??8?? patients with chronic low back pain due to chronic overloading, as ascertained via clinical assessment and magnetic resonance imaging, and 2??9?? 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.
Diaphragm activity was assessed under the following conditions:
?? Tidal Breathing:
After the initial synchronization between respiratory and MRI recordings, simultaneous synchronized respiratory and MRI recordings were taken.
??Isometric flexion of upper extremity:
The clinician placed his hands on the dorsal surface of the subject's forearms, which were at rest. The subject was then instructed to keep the elbows straight and flex both shoulders, attempting to lift the arms against the clinician's resistance, maintaining an isometric contraction. The muscle power generated by the subject corresponded to a grade 4 manual muscle test.
?? Isometric flexion of lower extremity:
The clinician placed his hands on the anterior surface of the subject's thighs while the subject remained at rest. The subject was then instructed to perform bilateral hip flexion against the clinician's resistance, maintaining an isometric contraction. The muscle power generated by the subject corresponded to a grade 4 manual muscle test.
*?? Diaphragm excursions or inspiratory/expiratory positions did not vary across patients and controls during TB without postural tasks. However, reduced diaphragm movement emerged when isometric flexion against resistance of the upper or lower extremity was applied, pointing to the importance of postural tasks in the expression of abnormal diaphragm function. The results provide additional evidence for altered breathing patterns during strenuous and nonstrenuous activity in individuals with low back pain. The findings may support the notion that the strategies utilized by the central nervous system to control core stability are altered in the presence of painful syndromes.
??Examiners found reduced diaphragm movement when isometric flexion against resistance of the upper or lower extremities was applied. The combined, more cranial position in the anterior and middle portions of the diaphragm and, particularly, the steeper slope between the middle and crural portions of the diaphragm in patients with chronic low back pain may contribute to low back pain symptoms. However, given that the results are based on cross-sectional analysis, we cannot exclude the possibility of reverse causation. Still, the results support the theory that patients with low back pain complaints present with compromised diaphragm function, which may play an important role in postural stability.