Ultrasonographic measurements of lower trapezius muscle thickness at rest and during isometric contraction: a reliability study

Abstract

Objective: The purpose of this study was to determine the intra-rater reliability and inter-rater reliability of ultrasound imaging (USI) thickness measurements of the lower trapezius (LT) at rest and during active contractions when the transverse process and the lamina were used as reference sites for the measurement process. Participants: Twenty healthy individuals between the ages of 22 and 32 years volunteered. Methods: With the subject prone and the shoulder in 145° of abduction, images of the LT were taken bilaterally by one examiner as the subject: (1) rested; (2) actively held the test position; and (3) actively held the test position while holding a weight. Ten subjects returned and testing was repeated by the same examiner and by a second examiner. LT thickness measurements were recorded at the level of the transverse process and at the level of the lamina. Results: Intra-class correlation coefficients (ICC) for within session intra-rater reliability (ICC_3,3) ranged from 0.951 to 0.986 for both measurement sites while between session intra-rater reliability (ICC_3,2) ranged from 0.935 to 0.962. Within session inter-rater reliability (ICC_2,2) ranged from 0.934 to 0.973. Conclusions: USI can be used to reliably measure LT thickness at rest, during active contraction and during active contraction when holding a weight. The described protocol can be utilized during shoulder examinations to provide an additional assessment tool for monitoring changes in LT thickness.

• Lower trapezius
• reliability
• ultrasound imaging