Reproducibility of a measurement for latissimus dorsi muscle length.

ABSTRACT Latissimus dorsi is a muscle theorized to undergo length changes due to shoulder region pathology or treatment such as stretching. A latissimus dorsi length measurement would be valuable to determine if length changes have occurred within an individual over time. With no such measurement known, we examined a proposed technique believed to isolate latissimus dorsi. The aim of this study was to determine how accurately a rater could reproduce this measurement in the same individual over a 6-week interval. Thirty subjects without shoulder symptoms were measured at 6-week intervals by either an experienced or novice clinician. A repeated-measures analysis of variance estimated the measurement error used for calculating intrarater correlation coefficients (ICC(3,1)). The standard error of measurement (SEM), confidence intervals (CI), and the smallest real difference (SRD) were also determined. The ICCs for all raters combined and for the separate groups indicated poor reliability. The SEM and SRD values were similar between groups, but they suggest poor measurement reproducibility in the same subject over a 6-week interval. This technique is not recommended for measuring latissimus dorsi length clinically to assess within-subject change over time.