Ultrasound measurement of deep and superficial abdominal muscles thickness during standing postural tasks in participants with and without chronic low back pain

Background: Activity of deep abdominal muscles increases the lumbar stability. Majority of previous studies indicated abdominal muscle activity dysfunction during static activity in patients with low back pain (LBP). However, the number of studies that evaluated deep abdominal muscle activity in dynamic standing activities in patients is limited, while this assessment provides better understanding of pain behavior during these activities. Objective: Investigation of superficial and deep abdominal muscles activity in participants with chronic LBP as compared to healthy individuals during standing tasks. Design: Case control study. Methods: Ultrasound imaging was used to measure the thickness of transverse abdominis (TrA), internal oblique (IO) and external oblique (EO) muscles in female participants with (N = 45) and without chronic LBP (CLBP) (N = 45) during tests. The Biodex Balance System was used to provide standing tasks. The thickness of each muscle in a standing task was normalized to actual thickness at rest in the supine lying position to estimate its activity. Results: The results indicate increases in thickness of all muscles in both groups during dynamic as compared to static standing tasks (P 0.5). Lower percentages of thickness change for TrA muscle and higher for EO muscle were found in the patients as compared to healthy individuals during all tests (P 1.28). Conclusions: Higher activity of superficial than deep abdominal muscles in patients as compared to healthy individuals during standing tasks indicates motor control dysfunction in patients with CLBP. Standing tasks can discriminate the individuals with and without LBP and can be progressively used in training.