Background: Low back pain (LBP) is one of the most common conditions in the United States. Dysfunctional patterns of the erector spinae (ES) and gluteus medius (GM) muscles often accompany episodes of LBP.
Objectives: To evaluate the intra-rater reliability of rehabilitative ultrasound imaging (RUSI) in obtaining thickness measurements of the ES and GM muscles at rest and during submaximal contraction.
Design: Single-group repeated-measures reliability study.
Methods: A volunteer sample of 30 adults with current LBP was examined. Thickness measurements of the ES and GM at rest and during contraction were obtained by using RUSI during a single session. Intraclass correlation coefficients (ICC) were used to estimate reliability. Reliability was further assessed by calculating standard error of measurement (SEM) and minimal detectable change (MDC).
Results: By using a mean of 3 measures, intra-rater reliability estimates ranged from 0.999 to 0.999 for ES, and 0.998 to 0.999 for GM. Reliability estimates for single thickness measures ranged from 0.997 to 0.998 for ES, and 0.995 to 0.997 for GM. Reliability estimates were lower for percent thickness change measures than the corresponding single thickness measures for all conditions.
Conclusions: RUSI thickness measurements of the ES and GM muscles in patients with LBP, when based on the mean of 3 measures, are highly reliable when taken by a single examiner in a single session.
Keywords: Erector spinae; Gluteus medius; Intra-rater reliability; Low back pain; Rehabilitative ultrasound imaging.
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