The Effect of Extraneous Movements on Peak Torque and Constant Joint Angle Torque-Velocity Curves

During isokinetic knee testing, some subjects flex the trunk and contralateral knee during knee extension and the trunk and contralateral knee during knee flexion. This investigation assessed the effect of these extraneous movements on peak and constant joint angle torque (15 degrees below horizontal). Twenty-one subjects performed isokinetic knee extensions and flexions at 60, 180, and 300 degrees/sec under stabilized and nonstabilized conditions. The nonstabilized testing was performed with intentional trunk and contralateral leg movements. The stabilized condition resulted in greater torque values than the nonstabilized condition for extension and flexion for both peak torque and constant joint angle torque. The angle at which flexion peak torque occurred was further from full extension at 60 and 180 degrees/sec under the nonstabilized condition, while no differences were found for extension. These results indicate that extraneous movements can decrease torque output, which may be due to changes in muscle length caused by the extraneous movements.