Ph.D., Associate Professor I.E. Popova
Ph.D., Associate Professor A.V. Sysoev
Voronezh State Institute of Physical Culture, Voronezh

Keywords: upper and lower limbs, excitability of motoneurons, arterial blood supply.

Introduction. Basketball is a sport that most strongly affects comprehensive development of man, improving his physiological indicators. Motor analyzer is under a heavy load during differentiated efforts related to the precision of movements during pointers and handlings. While playing the tricks are performed in constant contact and confrontation with an opponent that demands instant adjustments of athlete’s actions that differ from automatic practices, according to each specific situation [2].

At the same time the effectiveness of the execution of motor acts largely depends on the state of the neuromuscular system [10], functional properties of which are also determined by the intensity of the blood flow [3, 11] and the ratio of different types of tissue in the working limbs [7].

It is known that there are quantitative and qualitative changes in the state of the musculoskeletal system of athletes that come with age [6]. One of the main conditions of high efficiency of the system of training of athletes is strictly taking into account age and individual anatomical and physiological features characteristic of individual development stages of children and teenagers.

Hence, the purpose of the study was to identify the key parameters of peripheral hemodynamics and ratios of various types of tissues of working limbs that affect the functional state of the neuromuscular system of female basketball players, depending on their age.

Materials and methods. The objects of the study were female basketball players divided into three groups depending on their age. The group 1 was made of athletes aged 13-14 years (n = 10), the second - 15-16 years (n = 10) and the third - 19-30 years (n = 10).

The intensity of the peripheral circulation in the "shin" and "forearm" areas was studied using the method of rheovasography, for which purpose a hardware and software system of express-evaluation and monitoring of hemodynamic parameters on the basis of tetrapolar rheography and a personal computer with the appropriate software was used (rheoanalyzer KM-AR-01, St. Petersburg, Russia).

Regional blood flow was estimated by the following parameters: time of rapid blood supply (TRBS, seconds); time of slow blood supply (TSBS, seconds); systolic wave transmission time (SWTT, seconds); volume of blood flow through 100 cm³ of tissue per 1 minute (Vq100, ml/min); volume of blood flow through 100 cm³ of tissue per 1 heartbeat (Vs100, ml/min); rheographic systolic index (RI); amplitude-frequency indicator (AFI); maximum rapid filling velocity (Vmax, Ohm/s), average arterial blood filling velocity (Vav, Ohm/s), average rapid filling velocity (Vr, Ohm/s), average slow filling velocity (Vs, Ohm/s), average rheography indicator of pulse blood filling velocity (F, Ohm/s), venous-arterial index (V/А, %), rheogram amplitude (RA, Ohm), relative volume pulse (RVP), diastolic index (DSI, %), dicrotic index (DCI, %), vascular tone indicator (VTI, %), venous outflow coefficient (VOC), elasticity coefficient (EC).

Bioelectric activity of muscles was measured by means of the neuromyograph NMA-4-01 “Neuromyan”. The main research method was stimulation myography of the nerves Medianus (Med), Ulnaris (Uln), Tibialis (Tib). At the same time M-response was recorded from the muscles Abductor pollicis brevis, Abductor digiti minimi, Abductor hallucis. The results of the study were assessed by the following parameters: residual latency (RL, msec), latent period of the motor reaction (Lat, msec), M-response amplitude (A, mV), velocity of nerve impulse conduction to a nerve (V, m/s), M-response duration (D, msec).

In order to assess the conduction of the segmental arch that includes sensory, motor fibers outside of the spinal cord and its intraspinal part, as well as the level of excitability of motoneurons, H-reflex of the medial head of the Gastrocnemius muscle was recorded that was caused by the conventional method of the Tibialis nerve stimulation through a unipolar electrode, while the active electrode was placed in the popliteal fossa [5].

The following parameters of the data obtained were analyzed: percentage ratio of maximum amplitude of H-reflex to maximum amplitude of M-response (Н/М, %), latency period (Lat Н, msec), excitation threshold (Threshold Н, mA).

In order to study the return discharge of alpha-motoneurons in response to an antidromic excitation wave that originates in their axons in case of electrical stimulation of the peripheral nerve the technique of registration of the F-wave was applied ^[8]. Blocks (F blocks, %), repetitions and giant F-waves, the amplitude ratio of the F-wave to the M-response (А Fav./М, %), latency (LatF, msec), the nerve impulse conduction velocity calculated by the F-wave (VF, m/s) were analyzed.

The ratio of different types of tissue in the working limbs was determined by the impedansometry method using the body composition analyzer BC-418. The data obtained were analyzed for the following parameters: content ratio of fatty tissue (FAT, %); fatty tissue mass (FATmass, kg); fat free mass (FFM, kg); content ratio of muscle mass (PMM, kg).

Correlation analysis of the studied parameters was performed using the Statistiсa 10 software.

Results and discussion. Various correlations were detected between the studied parameters, only the crucial ones are presented in the tables.

While studying correlations between the parameters reflecting the functional state of the nervomuscular system as well as the indicators of the intensity of peripheral hemodynamics and tissue composition of arms of female basketball players of the 1^st group a significant strongly positive correlation was detected between V Uln and such parameters of arterial blood supply as F, Vav, Vr, Vs, RI, AFI, Vmx, EC (Table 1). The findings indicate that increase in the inflow of arterial blood to the upper limbs accelerates the nerve impulse conduction through the ulnar nerve resulting in increased hand muscle contraction velocity.

Table 1. Significant correlations between the neuromuscular system parameters and those of hemodynamics, as well as the ratio of various kinds of tissue of the upper limbs of female basketball players of the 1^st group

A strong significant negative correlation between D Uln and FFM as well as PMM was detected. It is known that the duration of the M-response indirectly reflects the whole range of neural conductibility through the nerve and depends on the synchronism of the impulse arrival to the muscle via peripheral neurons and the synchronism of motor units’ potentials appearance [4]. For this reason the detected correlation indicates that increase of the active mass in the upper limbs contributes to the improvement of the nerve impulse conduction through the ulnar nerve.

Improvement of neural conductibility of the median nerve is directly dependent on the decrease of fat mass, the time of rapid blood filling and increase of the peripheral tone of the upper limbs’ vessels (Table 1). An increase of the FATmass in the upper limbs promotes Lat Med growth, that indicating a decline in excitability of motoneurons of hand muscles.

In case of female basketball players of the 2^nd group increase in the excitability of motoneurons of hand muscles, the synchronism of the impulse arrival via the ulnar and the median nerves to the muscle and the synchronism of motor units’ potentials appearance positively affect the decrease of the venous-arterial index, that is, the intensification of arterial blood inflow to the limbs (Table 2). The established fact is confirmed by the detected negative correlations between RL Med and the parameters that characterize the intensity of arterial blood filling – Vav, Vr, Vs, Vq100, Vs100, Vmx, EC (Table 2).

Table 2. Significant correlations between the neuromuscular system parameters and those of hemodynamics and the ratio of various kinds of tissue of the upper limbs of female basketball players of the 2^nd group

The functioning of the neuromuscular system is negatively influenced by an increase of the fat mass in the upper limbs of the female basketball players of the 2^nd group. An increase of the active mass of the body, on the contrary, improves the neural conduction of the median and ulnar nerves.

Table 3. Significant correlations between the neuromuscular system parameters and those of hemodynamics of the upper limbs of female basketball players of the 3^rd group

The subjects of the 3^rd group had fewer significant correlations compared to the female basketball players of the 1^st and the 2^nd groups. Thus, it has been proved that the value of RL Med is negatively affected by excessive venous component over the arterial one and it is positively affected by an increase of inflowing arterial blood in the limb. Vs acceleration conditions Lat Uln decrease, thereby increasing the excitability of the hand muscles innervated by the ulnar nerve (Table 3).

Proceeding from the analysis of the findings, in case of female basketball players aged 13-14 years improvement of arterial blood filling of upper limbs mainly promotes acceleration of the nerve impulse in the ulnar nerve, while in case of female athletes aged 15-16 and 19-30 years promotes a decrease of RL of the median nerve, which indicates a reduction of the time of impulse conduction in the axon endings. Therefore, intensification of hemodynamics of the upper limbs of female basketball players contributes to the improvement of neuromuscular transmission aimed at developing the contraction velocity of the hand muscles that ensures quality performance of innings with one or two hands, dribbling the ball when changing from defense to attack, pointers while standing, moving and jumping.

Table 4. Significant correlations between the neuromuscular system parameters and those of hemodynamics, as well as the ratio of various kinds of tissue of the lower limbs of female basketball players of the 1^st group

In case of female athletes of the 1^st and 2^nd groups, active mass increase and decrease of fatty tissue in the upper limbs contribute to improvement of nerve conduction of the ulnar and median nerves. Such a dependence was not detected in female athletes of the 3^rd group. As we have previously shown, they have less fatty and more fat-free and relative muscle mass in their arms [9]. It is probable that a certain ratio of various kinds of tissue that is optimal for the chosen sport has been formed in skilled female athletes during a long period of adaptation to specific physical loads.

While analyzing the studied parameters of the lower limbs of female basketball players of the 1^st and 2^nd groups significant positive correlations were detected between V Tib and indicators of intensity of arterial blood supply (RA, F, Vav, Vr, Vs, Vq100, Vs100, RI, RVP, Vmx) and elasticity of blood vessels (EC). Negative correlations between the given hemodynamics parameters and RL Tib were shown too (Tables 4, 5).

In case of the young women of the 1^st group a negative correlation between DCI and V Tib and a positive one between DCI and RL Tib were detected, suggesting that increase in the tone of medium and small caliber helps reduce the speed of the nerve impulse conduction in the tibial nerve and increase the time of the impulse conduction in the axon endings. In case of female athletes of the 3^rd group improvement of the neuromuscular system function depends directly and only on such parameters as V/A and TRBS (Table 6).

Thus, an increase in the intensity of arterial blood inflow to the lower limbs improves excitation conduction through the tibial nerve, and this dependence is most pronounced in young female athletes. The data obtained are probably caused by the age development specifics of the neuromuscular system as well as by the duration of basketball training.

According to the study of the effect hemodynamics intensity has on the parameters of the F-wave, in case of female athletes of the 1^st group DSI and VOC increase promotes a Lat F decrease (Table 4), that is, the magnitude and the velocity of the venous outflow contribute to the improvement of nerve impulse conduction through the tibial nerve. In case of female basketball players of the 3^rd group a number of hemodynamics parameters contribute to acceleration of the nerve impulse conduction (Table 6).

Table 5. Significant correlations between the neuromuscular system parameters and those of hemodynamics, as well as the ratio of various kinds of tissue of the lower limbs of female basketball players of the 2^nd group

Young women of the 1^st group show significant positive correlations between the value of DSI and the parameters of V F, А F/M. Similar correlations are detected between TRBS and А F/M (Table 4). The findings indicate that an increase in tone of the large vessels and improvement of the blood outflow from the lower limbs contribute to increased excitability of motoneurons and their ability to respond.

Table 6. Significant correlations between the neuromuscular system parameters and those of hemodynamics, as well as the ratio of various kinds of tissue of the lower limbs of female basketball players of the 3^rd group

It has been established that in case of the subjects of the 2^nd and 3^rd groups an increased tone of great vessels leads to an increase in the number of gigantic F-waves, that is, to an increased probability of a simultaneous response of the maximum number of motoneurons of the foot muscles (Tables 5, 6).

During the study of H-reflex a significant positive correlation was detected between TRBS and Lat H of the female athletes of the 1^st group (Table 4). In case of the female basketball players of the 3^rd group it was found that an increase in the inflow of arterial blood to the lower limbs leads to an increase in the excitability of a pool of motoneurons of the gastrocnemius muscle and their increased synchronization (Table 6).

Thus, improvement of peripheral hemodynamics of limbs of female basketball players of different ages contributes to the formation of adaptive changes aimed at developing the responsiveness of muscles. The said quality is necessary to improve playing techniques of female basketball players and to achieve high results. Thus, E.Yu. Andriyanova showed an increased area of alpha motoneurons representation, the ones of the muscles of the upper and lower limbs with a high reflex excitability in the spinal cord of basketball players, which is an adaptive change in response to loads of variable intensity with a mixed structure of movements [1].

While analyzing possible correlations between the indicators of the neuromuscular system and the ratio of various types of tissue in the lower limbs of the testees it was proved that an increase of fatty tissue in the legs of female basketball players of the 1^st group contributes to increased excitability of motoneurons of the foot muscles and improved responsiveness of motoneurons (Table 4). This is probably due to the fact that the lower limbs of female athletes should not only ensure the proper functioning while moving on the court, but also to perform the supporting function.

In case of female athletes of the 2^nd and 3^rd groups no significant correlations were detected between the parameters of the neuromuscular system and the ratio of different types of tissue in the lower limbs.

Conclusion. As seen from the analysis of the findings, the intensification of arterial blood filling to the upper and lower limbs of female basketball players contributes to the improvement of the neuromuscular transmission, aimed at the development of contraction velocity of hands and feet muscles. The detected dependence is more pronounced in young athletes rather than older ones. Consequently, in order to develop speed of movement and increase the reaction rate of young female athletes one should include in their training process measures on enhancement of peripheral hemodynamics.

Senior female athletes, probably as a result of long-term adaptation to multiple repetitive motor acts, have formed mechanisms regulating the efficiency of the neuromuscular system functioning. This is confirmed by the data showing that the nerve impulse conduction in the upper limbs of female basketball players of the 3^rd group and in the lower limbs of female basketball players of the 2^nd and 3^rd groups does not depend on the amount of fat and active body mass, since these values have reached optimal numbers during their long-term basketball training.

To activate the neuromuscular transmission of the upper limbs of junior female athletes measures should be taken for them to lose weight and increase relative muscle mass, and in the lower extremities, on the contrary, - to increase fat mass.

While studying correlations between the studied parameters of the lower limbs it was found that in case of female basketball players the excitability and responsiveness of motoneurons, the impulse conduction velocity along the tibial nerve are largely influenced not only by the intensity of arterial blood filling, but also by the tone of the great vessels and the intensity of venous outflow.

Taking into consideration the hemodynamic characteristics of the upper and lower limbs as well as distribution of different types of tissue in them, it is possible to correct properly the process of sports training of female basketball players of different ages aimed at improving the neuromuscular system which contributes to performance of complex motor acts in the constantly changing situation on the basketball court, which determines the game results.

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