The Intra- and Inter-Rater Reliability of a Variety of Testing Methods to Measure Shoulder Range of Motion, Hand-behind-Back and External Rotation Strength in Healthy Participants

This study determined the intra- and inter-rater reliability of various shoulder testing methods to measure flexion range of motion (ROM), hand-behind-back (HBB), and external rotation (ER) strength. Twenty-four healthy adults (mean age of 31.2 and standard deviation (SD) of 10.9 years) without shoulder or neck pathology were assessed by two examiners using standardised testing protocols to measure shoulder flexion with still photography, HBB with tape measure, and isometric ER strength in two abduction positions with a hand-held dynamometer (HHD) and novel stabilisation device. Intraclass correlation coefficient (ICC) established relative reliability. Standard error of measurement (SEM) and minimum detectable change (MDC) established absolute reliability. Differences between raters were visualised with Bland–Altman plots. A paired t-test assessed for differences between dominant and non-dominant sides. Still photography demonstrated good intra- and inter-rater reliability (ICCs 0.75–0.86). HBB with tape measure demonstrated excellent inter- and intra-rater reliability (ICCs 0.94–0.98). Isometric ER strength with HHD and a stabilisation device demonstrated excellent intra-rater and inter-rater reliability in 30° and 45° abduction (ICCs 0.96–0.98). HBB and isometric ER at 45° abduction differed significantly between dominant and non-dominant sides. Standardised shoulder ROM and strength tests provide good to excellent reliability. HBB with tape measure and isometric strength testing with HHD stabilisation are clinically acceptable.