L.V. Kapilevich, professor, Dr.Med.
National Research Tomsk State University, Tomsk
F.A. Guzhov, postgraduate student
Yu.P. Bredikhina, Ph.D.
National Research Tomsk Polytechnic University, Tomsk
A.A. Il'in, Ph.D.
Tomsk State University of Control Systems and Radioelectronics, Tomsk

Key words: accuracy, coordination, unstable equilibrium, karate.

The physiological mechanisms that ensure the accuracy in striking a kick - geri were studied in athletes involved in sports karate at the main stages of improvement of sports skills. It is shown that the formation of skills in sports karate can be considered as a single functional system, in which coordination abilities, the manner of organization of muscular activity and development of its vegetovascular support systems play the leading role.

Introduction. Investigation of the physiological mechanisms that ensure the accuracy and coordination of motor actions is an important factor for improvement of sports skills [2, 3, 4]. Strikes in sports karate are a good model for such investigations [5, 7]. When striking the body weight is only on one leg. This body position is further complicated by the strong repulsion emerging at the time of kicking the target. Herewith, the target itself moves along the complex and hardly predictable trajectory [1, 6].

The purpose of the paper was to investigate the physiological mechanisms to ensure accuracy and coordination of movement under the conditions of unstable equilibrium and a moving target on the example of strikes in sports karate.

Materials and methods. The investigation involved 85 men aged 18 to 22 who were engaged in sports karate sections. They were divided into three groups. The first group consisted of 15 people with the categories of Master of Sport and Candidate Master of Sport; the second group - of 30 I-III Class athletes; the third group - of 40 people who did not have a sports category.

Coordination abilities and equilibrium were estimated using the stabilographic analyzer Stabilan-01-2 (SPA "Neurosoft", Russia). The electrobiological activity of the lower limb muscles was studied using the neuromyograph Neuro-MEP-4 (SPA "Neurosoft", Russia). Visual evoked potentials of the brain (VEP) were registered using the same device. Adaptive capabilities of the body of athletes were evaluated using the ECG-trigger-MCA-02 (SPE "Metex", Russia). Blood flow was estimated by means of rheovasography (RVG) using the rheograph "Rheo-Spectrum" (SPA "Neurosoft", Russia). The obtained data were statistically processed by the methods of variance and correlation analysis.

Results and discussion. Upon analyzing the statokinesiograms recorded at the time of striking a kick, it was found that at the preparatory phase the athletes from the group of masters maintained the common center of pressure (CCP) in the initial position, after which CCP shifted to the left in the frontal plane and forward in the sagittal one, along the trajectory of the kick, and then regressed (Fig. 1А).  For additional equilibrium, athletes with low- and mid-level skill levels shifted CCP to the right and left in the frontal plane as early as at the preparatory phase. At the time of striking a kick, the CCP trajectory was curved, which essentially negated the effectiveness of the performed movement. At the final phase, in order to maintain equilibrium athletes also performed oscillations (Fig. 1B). In terms of numbers, when performing a geri, with improvement of athletes' skills the CCP dispersion decreased in the frontal and sagittal planes, and so did the average velocity and the linear velocity of CCP in the same planes.

Fig. 1. Statokinesiograms when striking a kick (geri) in athletes of different sports qualifications

А - group of masters;
B - group of mid-level athletes;
C - group of beginner athletes.

Analyzing the electromyogram of the gastrocnemius muscle involved in the kick under study (Fig. 2), it is clearly seen that before striking a kick beginner athletes relax muscles deficiently. At the time of the kick, the maximum amplitude of the electrical activity increases significantly both in the upper and lower fascicles of the gastrocnemius muscle, with that, the best result was registered in the athletes from the group of masters (Fig. 2). Besides, with improvement of athletes' skills, the average frequency of oscillation increased in case of shorter duration of the activity cycle.

Fig. 2. Electromyogram of lower (I) and upper (II) fascicles of gastrocnemius muscle when performing a geri

А - group of masters;
B - group of mid-level athletes;
C - group of beginner athletes.

As follows from the comparison of the basic parameters of the blood-flow volume in the left and right feet, improvement of athletes' skills influenced the values of the bisferious index (BI), diastolic index (DI) and blood velocity (Vmax, Vavg). With improvement of skills, BI and DI increase at the left. While at the right the highest indices were registered in the group of athletes with mid-level skills. The lowest ones, as well as at the left, were observed in the group of beginner athletes. Also, improvement of athletes' skills promoted a decrease in Vmax and Vavg in both feet. The asymmetry of the blood-flow indices was observed in the rheographic indices of the calf, too. If at the right BI and DI increased with improvement of skills, at the left these indices decreased in the second group. The highest indices were registered in the group of masters.

Adaptive capabilities of the body of athletes were estimated by means of cardiointervalography. The mode amplitude (AMo) indices in the two first groups were significantly different from those in the group of beginner athletes and exceeded by 30%. The range of deviation (dX) increased only in the group of masters. The tension index (TI) was the lowest in the group of beginner athletes, but with improvement of their sports skills it increased first, while in the first group, on the contrary, it fell almost by half.

While studying visual evoked potentials (VEP) in karatekas, it was found that the latent period for negative components N1, N2, N3 in the anteriofrontal and occipital regions was significantly lower (p<0.05) in the group of masters and the group of mid-level skills compared with the group of beginner athletes. In the anteriofrontal region, the latent period of VEP for positive components Р1, Р2, Р3 was significantly lower (p<0.05) in the group of masters compared with the group of beginner athletes. The difference was the most pronounced in the components P2 and P3. The amplitude indices of such negative components as N1, N2, VEP increased with improvement of athletes' skills and in the group of masters prevailed in the anteriofrontal and occipital regions. The amplitude indices of the positive components Р1, Р2, Р3 were also the highest in the group of masters.

Conclusion. All the stated above proves that the formation of skills in sports karate can be considered as a single functional system, in which the leading role is played by coordination abilities and the manner of organization of muscle contraction. It is matching of the two systems that starts the formation of skills. Further improvement is accompanied with enhancement of their cooperation, based among other on optimization of the higher parts of the nervous system, which is expressed by shortening of the latent period and an increase in the amplitude of the late positive components of VEP.

Formation of this motor stereotype is accompanied with the development of its vegetovascular support systems. However, at the stage of improvement of sports skills, the level of tension of the autonomic nervous system is weakly correlated with motor loads, which leads to excessive stress of the regulatory mechanisms and hemodynamic imbalance. The relationships of motor and autonomic mechanisms are finally formed at the stage of elite sports skills.

References

1. Zinurova, N.G. The statokinetic stability indicators of athletes when adjusting to comprehensive coordination exercises / N.G. Zinurova, K.G. Denisov, M.M. Kuzikov // Vestnik YuUrGU. Series "Education, public health, physical culture”, 2011. Iss. 28. №26 (243). P. 127-130. (In Russian)
2. Kapilevich, L.V. The relationship between evoked brain potentials and special physical fitness of football players /L.V. Kapilevich, E.V. Zamulina // Vestnik sibirskoy meditsiny. Tomsk. 2008. № 2. P. 112-114. (In Russian)
3. Kapilevich, L.V. Coordination of paired motor actions of athletes (the case of ballroom dances) / L.V. Kapilevich, J.P. Bredikhina // Vestnik sibirskoy meditsiny, 2013. № 2. P. 204-210. (In Russian)
4. Kapilevich, L.V. Physiological monitoring of technical skills of athletes // Teoriya i praktika fizicheskoy kultury, 2010, №11. P. 12-15. (In Russian)
5. Lyakh, V.I. Coordination abilities: diagnostics and development. Moscow: TVT Divizion, 2006. 290 P. (In Russian)
6. Nakayama, M. Dynamics of karate / M. Nakayama. - Moscow: Fizkul'tura i
7. sport, 2003. - 457 P. (In Russian)
8. Krivoshchekov, S.G. Psychophysiology of sports addictions (exercise addiction) / S.G. Krivoshchekov, O.N. Lushnikov // Human Physiology. – 2011. – 37 (4). – Р. 509-513.

Corresponding author: kapil@yandex.ru