A comparison of concentric knee extension performance using the cybex 6000 nonpowered and powered mode for work and peak torque values

The purpose of this study was to examine whether there is a significant difference in isokinetic concentric knee extensor torque measured by the nonpowered mode versus the powered mode of the Cybex 6000. The non powered mode allows free acceleration, whereas the powered mode controls acceleration. The impact of this difference on measurements of work and peak torque has not previously been investigated. Thirty female volunteers with a mean age of 24.8 were sequentially assigned to groups that began testing on the powered mode while the alternates began on the non powered mode. All subjects were then tested on each mode of the Cybex 6000 at 180 deg/sec of maximal knee extension. The computer software of the Cybex 6000 calculated the mean of the peak torque and work values by averaging the last three of five test repetitions. Both the mean peak torque and the mean work values obtained in these two modes were then compared. The results of paired t tests indicated that there is no significant difference between mean peak torque values as measured during the non powered mode and the powered mode, nor was there a significant difference in mean work values found between these two modes. These results indicate that values of peak torque and work obtained from testing in these two modes may be accurately compared in the clinical setting. Clinicians should note that this study documents only that this equivalence exists at 180 deg/sec for concentric knee extension using the preprogrammed controlled acceleration rate of the Cybex 6000.