LAUSR

Abstract Background Altered scapular muscle activity is associated with abnormal scapular motions and shoulder pain. Hence, quantification of these activities is a challenging issue. Objectives: The purposes of this study were to establish the reliability of measuring levator scapula muscle thickness and to examine how thickness of this muscle changes with contraction. Methods Twenty-one asymptomatic individuals (mean age 22.29 ± 2.17 years) participated in this study. Three separate ultrasound images of the levator scapula muscle were captured at the neck-shoulder junction at rest and during a loaded isometric contraction. The procedures were repeated twice, four to seven days apart to establish intra-rater test-retest reliability. Interclass correlation coefficients (ICC) and standard error of measurement (SEM) were used to determine the reliability, and a paired t-test was performed to examine the difference in muscle thickness between two conditions. Results The results demonstrated that intra-examiner reliability was good at rest (ICC = 0.88, SEM = 1.16 mm) and excellent during loaded isometric contraction (ICC = 0.95, SEM = 0.91 mm). Furthermore, the thickness of levator scapula muscle significantly increased from rest to the loaded isometric contraction (Effect size = 1.99, P  Conclusion This study demonstrates that the thickness of the levator scapula muscle can be measured reliably at the neck-shoulder junction. Furthermore, ultrasound measures can reliably detect changes in muscle thickness from rest to a contracted state. Therefore, if the need exists to evaluate muscle morphology before and after any treatment strategy, thickness measurement of levator scapula can be determined reliably using ultrasound.