Reliability of ultrasound imaging for the measurement of abdominal muscle thickness in typically developing children

Introduction: A bdominal muscles are key to both posture andgait in both children with typical development (TD) and with disabilities.Ultrasound (US) imaging is a potential non-invasive method for investigatingactivity in these muscles. This study therefore aimed to determine the inter-tester and intra-tester reliability of B-mode US for investigating transverseabdominus (TrA ), rectus abdominus (RA ) and external- (EO) and internaloblique (IO) muscle activity in children with TD. Design: A  prospective cor-relational descriptive study.  Participants:  Eighty six, 6-13year old children from one private and one public mainstream school. Outcome measures: Two sets of B-mode US images where captured per subject during rest and during head-up, resisted head-up and resisted sling activities. Intra-class Correlation Coefcients (ICC) and standard error of measurement (SEM) were used to analyse the data. Results: Good correlation was found for both test - retest condi-tions for all four muscles tested during rest: 0.91(TrA ); 0.90(IO); 0.91(EO); 0.94(RA ) for intra-tester reliability and0.74(TrA ); 0.88(IO); 0.74(EO); 0.83(RA ) for inter-tester reliability. Repeatability of thickness measures during activity however showed variation in recruitment patterns. A  signicant correlation was found between age and BMI andresting abdominal muscle thickness (p<0.001). Conclusion: The study supports the reliability of US measurement of resting abdominal muscles and of the RA  under active conditions in children aged six to 13. However the stability o measurement of the other muscles under active conditions still needs to be established