reliability of shoulder rotators isometric strength test using a novel pulley electromechanical dynamometer. influence of the assessment position

Background: the shoulder complex, because of its relatively extensive freedom of motion, offers a great variety of testing positions and articular planes for strength examination. despite this, reliability of results are not clearly addressed. a novel pulley electrome- chanical dynamometer (fed) (functional electronic dynamometer) could be an alternative in strength assessment, however, the relative and absolute reliability have not been reported in the literature. objectives: to report the results of shoulder internal (ir) and rotators (er) peak torque reliability in two assessment positions by fed in asymptomatic subjects. methods: fifty-two healthy college students were included and tested twice within a two week period. in a supine position, the subjects randomly performed four isometric strength tests (i.e. ir at 40°, ir at 90°, er at 40°, and er at 90° of shoulder abduction). results: the intra-class correlation coefficients (icc) for relative reliability at 90° were 0.96 (0.94 - 0.98) for ir and 0.94 (0.90 - 0.96) for er. icc at 40° were 0.89 (0.80 - 0.94) for ir and 0.97 (0.94 - 0.98) for er. absolute reliability expressed as standard error of mea- surement compared to the mean (sem%) and 95% confidence interval (ci) of minimal detectable change percentage (mdc%) at 90° were 8.8% (-20.8, 28.4%) and 11.4% (-28.0, 35.2%) for er. mdc% at 40° were 12.6% (-35.5, 34.8%) for ir and 18.1% (-28.1, 35, 2%) for er. conclusions: isometric strength testing protocol using fed showed an excellent reproducibility and can be safely used in clinical settings to monitor the strength changes in a group of individuals or in a single individual.