Inter- and intra-rater reliability of a technique assessing the length of the Latissimus Dorsi muscle

BACKGROUND: Evidence-based practice requires the use of objective, valid and reliable tests for measuring the length of a muscle. Latissimus Dorsi is a muscle which undergoes length changes (loss of extensibility) and this muscle has a functional role in many aspects of sport and rehabilitation. The loss of extensibility may result in a decreased range of motion at the glenohumeral joint leading to dysfunction. OBJECTIVES: The aim of this study was to assess the inter-rater and intra-rater reliability of a technique adapted by Comerford and Mottram in 2012 for assessing the length of Latissimus Dorsi (LD) muscle. METHOD: Fifty-six students from a university’s physiotherapy department participated in this study. Four physiotherapists with clinical experience varying between 10 and 30 years independently performed the test for assessing the length of LD. The test was performed twice by each physiotherapist on every participant during two reading sessions. RESULTS: The intra-class correlation coefficient (ICC) as determined in a mixed-effects, generalised least squares regression analysis was used to assess inter- and intra-rater reliability of the LD length test. A 0.05 level of significance was employed. A sample of 56 participants provided an ICC that varied between 0.76 and 0.55, which is regarded as moderate to poor reliability. The ICC between the experienced raters was found to be 0.48, with a novice rater having an ICC of 0.48 as well. The ICC between all the raters was 0.33, which constituted poor reliability. CONCLUSION: The poor to moderate reliability of the technique testing the length of LD test is not suitable for application in a research setting. CLINICAL IMPLICATIONS: The small differences noted between Reading 1 and Reading 2 regarding the standard deviation of all the raters combined suggests that the LD length test may still prove to be useful in quantifying dysfunction in a clinical setting.