Resistive eccentric exercise: effects of visual feedback on maximum moment of knee extensors and flexors

One of the most important features of isokinetic dynamometry is the accurate assessment of muscular function. One of the main factors affecting the accuracy of isokinetic parameters during maximum activation efforts is visual feedback. The purpose of this study was the examination of the effects of visual feedback on maximum moment measurements of the knee extensors and flexors during isokinetic eccentric activations. Twenty-five males performed five maximal efforts at angular velocities of 30 degrees/sec and 150 degrees/sec with and without visual feedback on a Biodex dynamometer. Visual feedback was provided as real time display of the moment output. A three-factor analysis of variance test revealed significant differences between the moments recorded with visual feedback and the nonvisual feedback maximum moments of knee extensors and flexors at both speeds. The mean extension peak moments at 30 degrees/sec and 150 degrees/sec under visual feedback condition were approximately 7.2 and 6.4% higher than the nonvisual feedback moments, respectively. The increase for the knee flexor moment was 8.7 and 9% for slow and fast speeds, respectively. These findings suggest that visual feedback can improve maximum eccentric output and should be provided during assessment of maximum eccentric strength on an isokinetic dynamometer.