Postgraduate student G.S. Lalaeva¹
Postgraduate student A.N. Zakharova¹
Ph.D. A.V. Kabachkova¹
Postgraduate student A.A. Mironov¹
Professor, Dr.Med. L.V. Kapilevich^1
1National Research Tomsk State University, Tomsk

Keywords: EEG, attention, delta rhythm, theta rhythm, strength of nervous processes, sports training.

Introduction. Different sports are distinguished by specific requirements to the psychophysiological characteristics of those involved, and the training process affects the development of the functional capabilities of the body [1, 5, 6]. The degree of manifestation of various psychophysiological qualities influences the success of sports activity. Athlete's psychomotor, cognitive and mental states are the components of the psychophysiological states that occur during sports activities and reflect an integrated complex of the functional system elements [3, 9].

Objective of the study was to evaluate the psycho­physiological characteristics and indicators of bioelectrical activity of the cerebral cortex in athletes engaged in cyclic and endurance sports.

Materials and methods. Subject to study were men aged 17 to 20 years old. They were split into two main groups (cyclic and endurance athletes) consisting of 20 people each. All athletes were ranked higher than Candidate for Master of Sports. The reference group was made of 40 students (basic health group), who attended physical education classes twice a week and did not have any sports categories.

Psychophysiological testing was performed using the hardware and software complex NS-Psychotest (''Neurosoft'' Ltd., Russia). The strength of the nervous processes was estimated using the tapping test. The Shulte table method was used to evaluate the scope of attention to visual stimuli, the properties of attention allocation and switch, as well as to assess the speed of visual search.

EEG testing was performed using the hardware and software complex "Neuron-Spectrum 3" ("Neurosoft'' Ltd., Russia). The electrodes were located according to the international "10-20" system (installation of monopolar, reference electrodes - ear-clip). The indices were recorded in the sitting position with eyes closed in a state of relative rest (baseline record) and when taking the standard "eye-opening" and "eye-closing" tests.

The statistical data processing was made using the STATISTICA 8.0 software and implied determination of the sampling descriptive parameters, assessment of the normality of data distribution (Shapiro-Wilk’s test) and comparative analysis of the independent samples (t-test for independent samples, Mann–Whitney test). P£0.05 was taken as statistically significant difference.

Results and discussion. The analysis of the tapping test results indicates that the level of the initial tempo in the group of track and field athletes (8.6 Hz on the average) was statistically significantly higher than that in the other groups (p<0.05). The degree of performance decrement in the groups did not differ (from -32 to -31 c.u.). There were no differences in the stability of the nervous system - the ability to keep up the pace for a long time (-0.3 c.u. on the average in all groups).

When estimating the speed of visual search, the scope of attention to visual stimuli, the properties of attention allocation and switch, it was found that the degree of warming-up in the group of cyclic athletes (1.1 c.u. on the average) was statistically significantly higher than that in the reference group (p<0.05). The ability of track and field athletes to concentrate attention turned out to be higher and amounted to 26.4 (22.8; 38.5) c.u., compared to the referenced group - 36.8 (34.5; 44.4) c.u., and in the group of endurance athletes, on the contrary, lower - 42.1 (40.3; 43.8) c.u. (p<0.05).

EEG analysis revealed a number of significant differences in the nature of bioelectrical activity of the cerebral cortex (Table 1). After the eye-opening test we noted higher frontocentral alpha band activity, especially in the group of endurance athletes. The literature data testify to the specific display of different emotions in the alpha rhythm power: "fear" and "grief" suppress the alpha rhythm, while "joy" and "anger" make it increase [4]. An increase in the alpha activity in the group of endurance athletes may be due to greater "gusto" and higher emotionality.

Table 1. Rhythm amplitude changes in the frontal leads in the examined groups, Me (Q₂₅; Q₇₅)

Some studies revealed that the alpha rhythm is suppressed by emotional experiences, and its replacement by the delta rhythm reflects the development of the stress response [8]. The baseline record showed an increase in the average amplitude of the delta rhythm in the frontal lead in both of the groups of athletes (the index increased by 65% compared with the reference group). Moreover, in the group of endurance athletes, the mean amplitude of this rhythm exceeded the indices obtained in the group of cyclic athletes by 16%. In the central lead we also observed higher values ​​of the average amplitude of the delta rhythm in the group of cyclic athletes, whereas in the group of endurance athletes, they did not differ from the reference values. As to the occipital lead, endurance athletes had lower values of the average amplitude of the delta rhythm compared with the other groups, while in the group of cyclic athletes it still exceeded the reference values. Against the background of the eye-opening test, the described differences gain prominence. Apparently, cyclic athletes have a higher level of stress tolerance, as their training and competitive activities are related to direct competition, while endurance athletes lack this factor.

The beta rhythm (the frequency of 18-30 Hz) is greatly enhanced during various activities associated with the activation of the working mechanisms of the brain. It is believed that stress makes the beta rhythm increase considerably [2]. We observed the activation of the beta rhythm in all leads in the group of endurance sports, which can also indicate higher emotional intensity of sports activity in this group of athletes.

The question of the functional value of the theta rhythm remains the matter of debate today. However, there are facts allowing to consider this rhythm as an indicator of the state of psychophysiological orientation of man, an indicator of his/her emotional arousal, "the rhythm of tension" [7]. Despite the lack of information about the functional value of the theta band, there are reasons to associate the increase of this indicator with the processes of decrease of inhibition (or increase of excitation). The theta rhythm is particularly related to the process of remembering, as one of the theta rhythm generating structures is the hippocampus involved in the formation of the long-term memory traces. Increased activity of the theta rhythm in athletes can be due to the predominance of activation processes as a result of the regular patterns of motor activity, as well as new, quite complex movement patterns being formed in the process of improvement of technical skills. Against the background of the eye-opening test, the average amplitude of the theta rhythm in the frontal lead exceeded the reference values ​​in both of the groups of athletes, with that, in the group of endurance athletes it was higher than in the group of cyclic athletes. We noted higher values ​​of the average amplitude of the theta rhythm in the central lead only in the group of endurance athletes. There were no differences in the occipital lead between two groups.

Conclusions. Such psychophysiological qualities as the degree of warming-up and the ability to concentrate attention are more developed in cyclic athletes. They have also demonstrated higher initial tempo during the tapping-test. All this testifies to higher lability of the nervous processes in this group, and at the same time, the indices of endurance athletes do not differ from those of the reference group.

The mechanisms that predetermine the differences in the psychophysiological qualities of athletes of different specializations, are obviously associated with the organization of the activity of the cerebral cortex, formed by the regular repetition of certain patterns of motor activity. Endurance athletes were observed to have a significantly higher level of activity of the delta band in the frontal region at rest: ​​after the eye-opening test, it increases even more and covers all areas of the cortex. A similar trend was observed in cyclic athletes, but was less pronounced and with lower-level irradiation,. We noted higher frontocentral alpha band activity, especially in the group of endurance athletes, after the eye­opening test.

The obtained results suggest that certain patterns of EEG rhythms are specific for different kinds of sports activity and determine the range of psychophysiological characteristics of the athlete’s body.

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Corresponding author: kapil@yandex.ru