عنوان مقاله [English]
Background and objectives: Muscle fatigue may lead to imbalance and dysfunction of muscles. On the other hand, measuring imbalances between muscles should not be limited to measuring strength as it is not only parameter indicative of muscle function. Thus, the purpose of this study was to examine the effect of isokinetic fatigue protocol of quadriceps and hamstring muscles on mechanical power and time to peak torque in elite karate girls. subjects and Methods: In this study, 16 karate girls participated. Biodex isokinetic device was used for the local fatigue of quadriceps and hamstring muscles. The muscles mechanical power and time to peak torque at speeds of 180 and 300 degrees per second were measured by isokinetic device before and after the fatigue protocol. Data analysis was made by paired t test. Results: Mechanical power of quadriceps (P=0.004) and hamstring (P=0.000) muscle groups in speed of 300 degrees per second, significantly decreased after fatigue. But in the speed of 180 degrees per second, not significantly changed (P>0.05). Time to peak torque in speed of 180 degrees per second, showed a significant decrease after fatigue for the hamstring (P=0.04) and quadriceps (P=0.01), but in speed of 300 degrees per second, the difference was significant only for the hamstring (P=0.025). Conclusion: According to current study results, fatigue can cause an imbalance in mechanical power and time to peak torque between muscle groups at high speeds; that increases the chance of injury in the knee joint.