Abstract
The purpose of this study was to examine speed and mode specificity of strength training by comparing concentric and eccentric isokinetic exercises for extensors and flexors of the knee. The subjects were 28 healthy college students, randomly assigned to three groups: concentric training, eccentric training, and control. Peak torques corrected for the effect of gravity were obtained at four velocities (60, 120, 180, and 240 deg/sec) using a KIN-COM III isokinetic dynamometer. The control group was evaluated twice at an interval of 3 weeks, and the other groups were evaluated before training, 3 weeks later and 6 weeks. The concentric and eccentric groups trained with 6 to 8 sets of 10 maximal voluntary isokinetic contractions at 180 deg/sec. Training sessions were held three times a week for 6 weeks. The results showed that the concentric and eccentric strength of both flexors and extensors increased only slightly in the concentric group, but the eccentric group showed significant gains in concentric and eccentric strength at most speeds, in both flexors and extensors. The control group showed no significant change in concentric or eccentric strength at any speed. We concluded that the eccentric mode of isokinetic exercise increases strength more effectively than the concentric mode. Neither form of exercise at 180 deg/sec appears to have effects specific to speed or mode.
