Reliability of isokinetic internal and external rotation of the shoulder in the scapular plane

Abstract

This study has investigated the reliability of an isokinetic testing protocol for the shoulder rotators in the scapular plane to estimate the minimum variation of rotator moment needed to detect a significant change between two tests. Concentric and eccentric actions of shoulder internal and external rotation were assessed in a group of 31 male students. Measurements were performed on the dominant and non-dominant sides, at 60 and 120 ◦ ·s −1 , using an isokinetic dynamometer. Each volunteer was assessed in the seated position, with the arm at 45 ◦ of abduction and 30 ◦ of horizontal adduction. The intraclass correlation coefficient (ICC 3,1), the standard error of measurement (SEM) and the limits of agreement (LOA) were used to determine inter-session reliability and the magnitude of the measurement error for gravity corrected peak and average moment. Moderate to high ICC values (0.76– 0.93) were observed for all measured variables. The measurement error associated with repeated measures ranged between 3.9–13.3 Nm. Both SEM and LOA revealed greater measurement errors for peak compared to average moment, eccentric compared to concentric actions, and internal compared to external rotation. The findings of the present study suggested that decline or improvement in isokinetic shoulder rotator moment should only be considered as a significant response to a pathology or an intervention, when the moment data obtained in consecutive repeated measures is lower or greater than the measurement error.