Measuring shoulder rotational strength and range of motion: a comprehensive intra-rater, inter-rater and test-retest reliability and validity study of several testing protocols


Accurate assessment of shoulder range of motion (ROM) and shoulder strength are important aspects in the clinical setting, especially for patient’s status and progression overtime. The purpose of this study was to establish absolute and relative reliability and validity for several procedures measuring the shoulder ROM and strength for internal (IR) and external rotation (ER) with new tools e.g. the EasyAngle and Jamar.

Study Details

Authors – Dr Ann Cools: Ghent University Hospital

Year of study – 2014.


Thirty healthy individuals (15 males, 15 females), with a mean age of 22.3 +/- 1.8 years, were examined by 2 examiners who measured the ROM with a goniometer, inclinometer and the EasyAngle. Secondly the isometric strength was measured with a handheld dynamometer (HHD) and the Jamar in different shoulder positions. Relative reliability was determined by intraclass correlation coefficients (ICC). Absolute reliability was quantified by standard error of measurement (SEM) and minimal detectable change (MDC). The validity was determined by the Pearson correlation coefficient. Systematic differences across trials or between testers, as well as differences among similar measurements under different testing circumstances, were analysed with dependent t-tests.


The intra-rater reliability for the ROM measurements shows excellent results for all the procedures (ICC, 0,931-0,991) but the inter-rater reliability shows low to moderate results (ICC, 0,439-0,774). The reliability for the isometric strength was excellent for all procedures (ICC, 0,843-0,967). For some of the measurements, systematic differences were found across trials or between testers. The subjects position and the equipment resulted in different outcome measurements.


All procedures examined showed acceptable reliability for clinical use. However, the subjects position and equipment might influence the results.

Link to study online: here.


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