Inter-Rater Reliability of Ultrasound Imaging of the Trunk Musculature Among Novice Raters

Objective The purpose of this study was to determine the inter-rater reliability of ultrasound imaging for assessing trunk muscle morphologic characteristics at rest and while contracted among different pairs of novice raters. The secondary purpose was to compare 3 different measurement techniques for assessing lateral abdominal muscle thickness. Methods A single-group repeated measures reliability study was conducted on 21 healthy participants (mean ± SD, 21.5 ± 4.4 years; 5 female and 16 male) without low back pain. Ultrasound images of the transversus abdominis, internal oblique, rectus abdominis, and lumbar multifidus muscles were obtained by different pairs of novice raters in a counterbalanced order. All raters received a standardized training program before obtaining measurements. Results The intraclass correlation coefficient (1, 3) point estimates ranged from 0.86 to 0.94; the standard error of the measurement ranged from 0.04 to 0.16 cm for the thickness values and 0.67 cm2 for the cross-sectional area of the rectus abdominis muscle. There was no meaningful difference between the different measurement techniques used to analyze the lateral abdominal muscles. Conclusions Good to excellent reliability was obtained for all measures by novice raters. Minimal differences in reliability were noted between the different measurement techniques to assess lateral abdominal muscle thickness.