Abstract
The examination of moment and electromyographic (EMG) activity-angle curves of the agonists and antagonists is important for the determination of the mechanisms responsible for moment production during maximal activation of knee extensors and flexors. The purpose of this study was the examination of agonist and antagonistic activity of knee extensors and flexors at different knee joint angles during isokinetic exercise. Twelve females performed maximum isometric, eccentric and concentric isokinetic efforts of knee extensors and flexors on a Biodex dynamometer. The isokinetic tests were performed at angular velocities of 30, 60, 90, 120 and 150° Is. The EMG activity of vastus lateralis, rectus femoris, vastus medialis and hamstrings was also recorded. The knee extensor and flexor maximal activity was found at angles ranging from 50° to 70° and from 20° to 40°, respectively. The antagonist activity was greater at the initial and final stages of the movement. Three way analysis of variance designs indicated significant differences in the agonist and antagonistic activity of knee extensors and flexors between eccentric and concentric exercise. The results of this study demonstrate that, despite changes in magnitude, the moment-angle and IEMG activity-angle patterns of the agonists were not affected by angular velocity and muscle action conditions. On the contrary, the IEMG activity-angle curves of the antagonists during maximal isokinetic voluntary efforts are affected by angular velocity conditions but were independent of the type of muscle action examined.