The understandings of the characteristics of eccentric exercise are very important because all sports and daily activities under the gravity force should be well coupled between concentric contraction and eccentric contraction as accelerator and decelerator respectively. We tested 40 knee flexors and extensors of 20 normal young persons at different anglular velocities of 60^o/sec and 120^o/sec using Cybex 6000(A division of Lumax, New York) isokinetic dynamometer in order to know the characteristics of eccentric isokinetic contraction parameters by comparing with concentric isokinetic parameters.

Compared to the concentric isokinetic contraction, eccentric isokinetic the peak torque and average power values of knee extensor and flexor muscles showed negative values which means that eccentric contractions were coupled with concentric contractions as decelerator and energy absorptioner. The peak torque values of eccentric contraction were 38∼61%, 44∼79% higher in flexor and extensor, respectively than those of concentric contraction and not so decreased as the peak torque of concentric contraction decreased in high angular velocity. The average power values of knee flexor and extensor muscles were definitely low in eccentric contracton than those of concentric contraction but were increased simultaneously with high angular velocity contraction. Further studies about the velocity dependency, muscle soreness, methodology to measure real eccentric activities and other parameters of eccentric contraction are needed imminently.