Reliability of the ultrasound measurements of abdominal muscles activity when activated with and without pelvic floor muscles contraction

BACKGROUND: Synergistic co-activation of the abdominal and pelvic floor muscles (PFM) has been shown in literature. Some studies have assessed the reliability of ultrasound measures of the abdominal muscles. OBJECTIVE: The aim of this study was to determine the reliability of ultrasound measurements of transverses abdominis (TrA) and obliquus internus (OI) muscles during different conditions (PFM contraction, abdominal hollowing manoeuvre (AHM) with and without PFM contraction) in participants with and without chronic low back pain (LBP). METHODS: 21 participants (9 with LBP, 12 healthy) participated in the study. The reliability of thickness measurements at rest and during each condition and thickness changes and percentage of this changes at different conditions were assessed. RESULTS: The results showed high reliability of the thickness measurement at rest and during each condition of TrA and OI muscles, moderate to substantial reliability for the thickness change and percentage of thickness change of TrA, and fair to moderate reliability of the thickness change and percentage of thickness change of OI in both groups. CONCLUSIONS: Ultrasound imaging can be used as a reliable method for assessment of abdominal muscle activity with and without PFM contraction.