Are isokinetic leg torques and kick velocity reliable predictors for competitive success in taekwondo athletes?

The aim of the study was to analyzed the relationship between isokinetic knee and hip peak torques and Roundhouse-kick velocities and expertise level (Elite vs. Subelite) of Taekwondo athletes. Seven elite and seven sub-elite athletes were tested for kick kinematic, power of impact and for isokinetic peak torque (PT) at slow (60°/s) and high (240°/s) concentric mode. PTs were compared between groups and correlated with the data of kick performance. It was found inter-group differences in hip flexors and extensors PT at the isokinetic fast speed. The hip flexion PT at 60°/s and 240°/s were negatively correlated with the kick time (R = −0.46, and R = −0.62, respectively). Hip flexion torque at 60°/s was also positively correlated (R = 0.52) with the peak of linear velocity of the foot (LVF) and the power of impact (R = 0.51). Peak torque of hip extension at 60°/s and hip abduction at 240°/s were correlated with the LVF (R= 0.56 and R = 0.46). Discriminant analysis presented an accuracy of 85.7% in predicting expertise level based on fast torques of hip flexion and extension and on the knee extension velocity during the kick. This study demonstrated that hip muscles strength is probably the dominant muscular factor for determining kick performance. Knee angular velocity combined with hip torques are the best discriminators for the competitive level in taekwondo athletes.