Introduction: 

In karate, the roundhouse kick (RK) could be a good model to show the ability of a karateka to perform complex actions combining high movement velocities with high precision. The neuromuscular control adopted by karateka during the Low Roundhouse Kick (LRK) and High Roundhouse Kick (HRK) was then studied.

Methods: 

Surface electromyographic (sEMG) signals were recorded from the Vastus Lateralis (VL), Rectus Femoris (RF), Biceps Femoris (BF), Gluteus Maximum (GM) and Gastrocnemious (GA) muscles during the LRK and HRK in six elite Karateka (K) and six Controls (C) (25±1yrs; 1.78±0.03m; 73.8±4kg). The Co-activation index (CI) of antagonist vs. overall activity was computed for knee and hip flexion and extension. For the knee joint three CIs were computed: extension with mono and bi-articular muscles (KCIextM and KCIextB, respectively), and flexion (KCIflex). For the hip joint, the Hip flexion (HCIflex) and Hip extension (HCIext) CIs were calculated. Muscle Fiber Conduction Velocity (CV) obtained from VL and BF muscles was assessed as well. The effect of Group (K and C) and Kick (LRK and HRK) on CI and on VLCV and BFCV was tested through a two-way ANOVA (p<0.05).

Results: 

The ANOVA demonstrated an effect of Group on all CIs computed (p<0.001). Karateka showed lower HCIflex, KCIextM and KCIextB and higher KCIflex and HCIext. BFCV was higher in K compared to C for both LRK (5.1±2.0 vs. 2.5±1.3 m*s-1) and HRK (5.7±2.6 vs. 3.5±1.9m*s-1, p<0.05).

Discussion: 

Karateka demonstrated a peculiar muscle activation strategy with respect to Controls and showed an improved ability to recruit fast MUs as a part of training induced neuromuscular adaptation.