Background Shoulder strength assessment plays an important role in the clinical examination of the shoulder region. Eccentric strength measurements are of special importance guiding the clinician in the injury prevention or return to play decisions after injury.

Objective The primary aim of this study was to examine the absolute and relative reliability and validity of a standardized eccentric strength measurement protocol for the glenohumeral external rotators.

Design Reliability and Validity study.

Setting Testing environment at the department of Rehabilitation Sciences and Physiotherapy of the Ghent University, Belgium.

Participants 25 healthy subjects (9 male and 16 female) without any history of shoulder pain were tested.

Risk factor assessment The subjects were tested by two independent assessors using a hand-held dynamometer (HHD), and underwent an isokinetic testing procedure. A clinical protocol, using a HHD, a Dynaport accelerometer to measure acceleration and angular velocity and a Biodex to measure isokinetic testing was used.

Main outcome measurements Three (3) eccentric strength measurements: (1) tester one with the HHD, (2) tester two with the HHD, and (3) Biodex isokinetic strength measurement.

Results The intratester reliability was found to be excellent (0,879 and 0,858), whereas the intertester reliability was good with an ICC between testers of 0,714. Pearson correlation coefficients of 0,78 and 0,70 were found between the HHD and the isokinetic data, showing good validity of this new procedure.

Conclusions This study shows that standardized eccentric rotator cuff strength can be measured and performed in the clinical setting with good to excellent reliability and validity using a HHD.