Technical report: Reliability and validity of the iSAM 9000 isokinetic dynamometer

This study assessed the mechanical reliability and validity of the INRTEK iSAM 9000 isokinetic dynamometer, and compared the obtained torque values of the prototype device with those from a traditional device. Sixty volunteers (40 men and 20 women) were tested at 60 degrees per second for shoulder, knee, and trunk flexion, and extension on both the Cybex 6000 and a new isokinetic dynamometer (iSAM 9000). Intraclass correlation coefficients (ICC) and standard errors of measurement (SEM) revealed a high level of reproducibility and precision in the device's torque measurements (ICC range = 0.94-0.98; SEM range = 5.2-29.7). Pearson r values revealed very high relationships between the two instruments (set 1: r = 0.84-0.93; set 2: r = 0.87-0.93; P < 0.05). Significantly higher peak torque for both sets of left and right knee flexion and extension, right shoulder extension and trunk extension was found for the iSAM 9000 compared to the Cybex 6000 (P < 0.05). The strong ICCs and small SEMs support the device's mechanical reliability and validity. The high correlation coefficients between the prototype dynamometer and the Cybex 6000 support the new device's validity in the measurement of isokinetic torque. The findings of this study will be used to refine the next generation of the INRTEK isokinetic device with respect to test protocols and the reliability of measuring human muscle performance.