Correlations between core muscle geometry, pain intensity, functional disability and postural balance in patients with nonspecific mechanical low back pain

Patients with low back pain (LBP) have reduced core muscle geometry and impaired postural balance. Impaired trunk control was shown to be associated with poor balance and limited functional mobility in these patients. However, the relationship between muscle geometry and postural balance is unclear. This study aimed to determine the correlation of core muscle geometry with pain intensity, functional disability and postural balance in patients with chronic nonspecific mechanical LBP. Thirty patients aged 20-50 years were enrolled. Ultrasound imaging was used to assess their muscle geometry. The participants completed a numerical rating scale (NRS) for pain severity, and the Persian version of the Roland-Morris Disability Questionnaire (PRMDQ). To estimate static balance, they were asked to perform the single leg stance test. Dynamic balance was assessed with the Y-balance test. Significant correlations were found between NRS scores and bilateral multifidus cross-sectional area during rest (r ≥ − 0.31, P ≤ 0.04) and contraction (r ≥ − 0.37, P ≤ 0.02). NRS scores correlated significantly with bilateral multifidus thickness during rest (r ≥ − 0.31, P ≤ 0.04) and contraction (r ≥ − 0.28, P ≤ 0.04). Significant correlations were also observed for PRMDQ scores with thickness (r ≥ − 0.35, P = 0.04) and cross-sectional area of the multifidus muscles (r ≥ − 0.33, P = 0.04) bilaterally during contraction. A significant correlation was found between Y-balance scores and right abdominal muscle thickness during rest and contraction (r ≥ 0.34, P ≤ 0.04). Core muscle geometry correlated with pain, functional disability indices and dynamic balance in these patients.