The Effect of Concentric Isokinetic Strength Training of the Quadriceps Femoris on Electromyography and Muscle Strength in the Trained and Untrained Limb

The purpose of the present investigation was to examine the effects of unilateral concentric isokinetic leg extension training on peak torque (PT) and electromyographic (EMG) responses in the trained and untrained limbs. Twenty adult men were randomly assigned to a training (TRN, n = 11) or control (CTL, n = 9) group. The TRN group performed 6 sets of 10 leg extensions 3 days per week for 12 weeks at a velocity of 90°·s^-1. All subjects were tested every 4 weeks for PT and EMG responses of both legs at a velocity of 90°·s^-1. The 3-way mixed factorial analysis of variance (ANOVA) indicated a significant (p < 0.05) increase in PT over the 12 weeks in both the trained and untrained limb for the TRN group but no significant change in PT in either limb for the CTL group. The results of the 3-way ANOVA for the EMG data indicated no significant change in EMG amplitude in the trained or untrained limb for the TRN or CTL group. The increase in PT in the absence of a change in EMG may result from hypertrophic factors and/or changes in the other muscles or muscle groups involved in leg extension.