Reliability of transversus abdominis and internal oblique muscle thickness measurement using B-mode ultrasound imaging in standing and single leg standing positions
Authors:   Department of Physical Therapy, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai Province, Thailand., Soontornthip Jitsak , Leonard Joseph Henry ,   School of Sports and Health Sciences, University of Brighton, Eastbourne, BN20 7UR, East Sussex, United Kingdom., Sriburee Sompong ,   Department of Radiologic Technology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai Province, Thailand., Chamnongkich Samatchai ,   Department of Physical Therapy, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai Province, Thailand., Paungmali Aatit ,   Department of Physical Therapy, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai Province, Thailand., Pirunsan Ubon ,   Department of Physical Therapy, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai Province, Thailand., Sitilertpisan Patraporn ,   Department of Physical Therapy, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai Province, Thailand.
Published: December 2022

Background: The thickness of the transversus abdominis (TrA) and internal oblique (IO) muscles are measured with high reliability by musculoskeletal ultrasound imaging (MSUSI) in the supine hook-lying and walking position. However, the reliability of the procedure to measure the TrA and IO muscle thickness measurement in the functional positions such as standing and single leg standing positions have not been well established. Objectives: To examine the reliability of MSUSI for the TrA and IO muscles thickness measurement during standing and single leg standing positions in healthy participants. Materials and methods: Ten healthy participants (aged 24.10±2.47 years) were recruited to perform MSUSI measurement of TrA and IO muscle thickness during the resting and abdominal drawing in maneuver (ADIM) in the standing and single leg standing positions. The intra-tester reliability of MSUSI measurement was performed by the same investigator in 2 different times (24 to 72 hours apart), while the inter-tester reliability was performed by 2 investigators within the same day. The intraclass correlation coefficient (ICC) whereby ICC3,3 was used to determine the intra-tester and ICC 2,3 was used to determine the inter-tester reliability of TrA and IO muscles thickness measurement using MSUSI. The standard error of measurement (SEM) and coefficient of variation (CV) were calculated. Results: The MSUSI measurements for TrA and IO muscles thickness showed high reliability in both standing and single leg standing positions (ICC3,3 and ICC2,3 >0.9). Moreover, the values of SEM ranged between 0.055 to 0.662 mm, MDC ranged between 0.152 to 1.834 mm and CV ranged between 0.543 to 14.001%. Conclusion: The MSUSI measurement of TrA and IO muscles thickness could be performed with high intra and inter-tester reliability in standing and single leg standing positions among healthy individuals. The study findings on the MSUSI procedure to measure muscle thickness of TrA and IO would be useful for practice guidance in various research and clinical settings.