AMPLITUDE AND FREQUENCY FEATURES OF THE SURFACE ELECTROMIOGRAMME IN KARATE STANCES
Keywords:
Kyokushin Karate, Fudo dachi, Zenkutsu dachi.Abstract
Abstract. Improvement of the athlete’s performance of exercises requires a detailed analysis of muscle activity, aimed at achievement of the optimal model of motor activity regulation. The study of the electrical activity of separate athlete’s muscles makes it possible to describe their role in performance of movements or maintaining of stances. The aim of our study was to examine the features of the electrical activity of some muscles of karate athletes during the standard Kyokushin Karate stances (Dachi Waza). The study involved 16 highly qualified karatekas (I Dan), aged 18–25 years, with training experience of 12–17 years. Surface electromyogram (sEMG) was recorded during the basic Fudo dachi and Zenkutsu dachi stances for the following muscles: m. gluteus maximus, m. rectus femoris, m. biceps femoris, m. semitendinosus, m. gasterocnemius (caput lateralis), m. tibialis anterior. In the Fudo dachi, the mean amplitude and mean sEMG frequency are low (up to 38 % of the maximum), and no right-left asymmetry of sEMG parameters was detected. The low levels of the activity of the muscles of lower extremities, along with the symmetry of the activity of muscles from right and left body sides, is found to be in good agreement with the description of the performance of the stand. However, the relatively high electrical activity of some leg (21–23 % of the maximum) and foot (24–26 %) flexors is somewhat unexpected. In Zenkutsu dachi the higher (up to 45 % of maximum) mean sEMG amplitude of some karateka’s leg muscles, including m. tibialis anterior d. and m. rectus femoris d. et s have been found. For the right extremity, the higher indexes of sEMG are found for of hip extensors, leg flexors and foot extensors, and the lower – for the foot flexors (P<0.05), as compared to the left one. The obtained sEMG indicators are mainly consistent with the description of features of the stance performance. Thus, significant (41 % of maximum) level of the electrical activity of leg extensor of the front leg indicates a high muscle tension due to a significant load. Although, the athletes’ attempts to keep the back leg as straight as possible cause the activation of both extensors (41 % of the maximum) and flexors (25–33 %) of the leg. Relatively high level of the muscle tension of back leg can be considered as a certain deviation from correct technique of the stance performance. The sEMG analysis suggests that there is a predominance of the frequency mechanism of increasing the strength of muscles contraction during the stance performance over the recruitment of motor units.
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