Diaphragm excursion and thickness in patients with chronic low back pain with and without lumbar instability

Diaphragm is crucial for respiration and plays a significant role in trunk stabilization, particularly during postural tasks. Several studies have focused primarily on trunk muscles in lumbar instability (LI) patients. However, the role of diaphragm remains underexplored. Therefore, this study aimed to compare diaphragm excursion, diaphragm thickness, and lung function represented by predicted percentage of forced vital capacity (%FVC predicted) during a load-lifting at tidal breathing between CLBP patients with (CLBP_LI) and without LI (CLBP_NLI). Ninety-six participants with CLBP, aged between 20 and 59 years, were divided into CLBP_LI and age-matched CLBP_NLI groups based on screening tools and clinical tests. Diaphragm excursion and diaphragm thickness were assessed using real-time ultrasound imaging during load-lifting with tidal breathing. Additionally, lung function was measured using a spirometer. CLBP_LI group had significantly decreased total diaphragm excursion (p-value = 0.003) and diaphragm thickness at inspiration (p-value = 0.027) and expiration (p-value = 0.34) compared to CLBP_NLI group. There were no differences between the groups in excursions during inspiration and expiration, total thickness, thickness change, and %FVC predicted. Individuals with CLBP_LI exhibited decreased diaphragm excursion and diaphragm thickness during inspiration and expiration. Addressing diaphragm training in rehabilitation programs may lead to more effective treatment outcomes for LI patients.