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^{\circ}
\cdots^{-1},
using an isokinetic dynamometer. Each volunteer was assessed in the seated
position, with the arm at 45^{\circ} of abduction and
30^{\circ} 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.
