Reliability of sonography measures of the lumbar multifidus and transversus abdominis during static and dynamic activities in subjects with non-specific chronic low back pain

Purpose: The purpose of this study was to investigate the test-retest reliability of ultrasound (US) thickness measurements and the muscle contraction ratio (CR) of lumbar multifidus (LM) and transversus abdominis (TA) muscles in participants with and without nonspecific chronic low back pain (NCLBP). Methods: A total of 62 participants (37 with NCLBP, 25 without NCLBP) with participated in the study. The within-day and between-day reliability of US thickness measurements and CR in a lying (supine for TA and prone for LM) and sitting positions for both muscles (sitting on a gym ball with both feet on the ground or lifting one foot off the floor) were assessed. Reliability analysis was performed with intraclass correlations (ICCs) for these two static and dynamic positions. Results: Test-retest reliability was calculated to be good to high for the static position (ICC = 0.72–0.95) and the dynamic position (ICC = 0.74–0.94) sonographic measurements in both group of TA measurement. Test-retest reliability of LM measurements was good to high for the static position (ICC = 0.82–0.95) and the dynamic position (ICC = 0.85–0.97) sonographic measurements in both groups. Conclusions: US imaging is a highly reliable method for the assessment of TA and LM thickness muscles in the dynamic position in participants with and without NCLBP. The CR measures may be adequately reliable in assessing the function of the TA and LM muscles in participants with NCLBP and healthy ones.