Development of coordination abilities in 17–20 year old tennis players



The object of the study is 17–20 year old tennis players.

The subject of the study is the development of coordination abilities of tennis players 17–20 years old.

The aim of the research is to develop and scientifically substantiate the program of development of coordination abilities of tennis players of 17–20 years old.

Research methods: theoretical analysis and synthesis of information sources, sociological methods (questioning), pedagogical observation, educational experiment, pedagogical testing, methods of mathematical statistics.

Elements of novelty: for the first time the use of the program of development of coordination abilities of tennis players 17–20 years old is developed and experimentally proved. During the study quantitative data of indicators characterizing coordination abilities as well as the influence of their development on other physical qualities of tennis players are obtained.

The results of the study are implemented in the educational process of EE «Vitebsk State College of Olympic Reserve». Materials are used in the lecture course, practical classes in the disciplines «Physiological foundations of physical culture and sports» and «Theory and methodology of physical culture and sports».

Theoretical and practical significance: the results of this study complement and clarify ideas about the development of coordination abilities. The developed program can be used for the development of coordination abilities of tennis players in the process of their training, as well as for independent training sessions. General provisions and recommendations of this work can be used at all stages of training tennis players, as well as in the educational process when teaching the relevant disciplines.

Keywords: coordination, coordination abilities, tennis training, tennis athletes, coordination exercises, physical qualities.

Introduction

The problem of human movement coordination is not only a major theoretical problem in many disciplines, such as the humanities, movement control, skills training, rehabilitation medicine, and behavioral psychology, but also has a large application space in the fields of ergonomics, child skills development, and sports training.

The ability to coordinate movements is a basic ability that the human body must possess in sports. It is the prerequisite and basis for learning and using sports technology. It directly affects the mastery of sports technology, the use of techniques and tactics, as well as the improvement of sports performance. Currently, there are many findings in the domestic and foreign literature on motor coordination ability. However, since studies of motor coordination are not organically combined with the characteristics of specific competitive sports, this has prompted athletes and coaches to use the training and practical application of motor coordination abilities. Underestimating the importance and necessity did not provide a theoretical basis and objective standards for scientific selection of athletes, measurement and evaluation of athletic coordination, training and practice, and overlooked the competitive athletic value of motor coordination.

Once tennis has become an official event of the Olympic Games, it has received widespread attention. The level of professionalism of athletes in different countries is getting higher and higher, which contributes to the rapid development of tennis skills and tactics, as well as puts higher and higher requirements on the coordination abilities of athletes. The coordination ability of a tennis player is one of the important factors determining the competitiveness of a tennis player. It is a complex reaction of tennis player's speed, strength, endurance, agility, flexibility and other qualities under the control of central nervous system in space and time. Young tennis players have good coordination skills. This ability is a prerequisite and basis for smooth learning and mastering different techniques. It is also the basis for their free and flexible control of their body according to the rapid changes of the game situation during the game. This tennis technique is an important guarantee of improvisation. In the literature there are many studies of tennis based on the basic theoretical knowledge of tennis, the technical and tactical characteristics and the psychological level of the athletes. However, there are very few studies on coordination training in tennis. Thus, the problem of developing coordination abilities of tennis players is relevant because improving their coordination abilities will improve their technique and training effects as well as provide professional training in the future.

The object of the study is 17–20 year old tennis players.

The subject of the study is the development of coordination abilities of tennis players 17–20 years old.

The aim of the research is to develop and scientifically substantiate the program of development of coordination abilities of tennis players of 17–20 years old.

The objectives of the research:

1. To study factors and ways of development of coordination abilities of tennis players.
2. To develop the program for development of coordination abilities of tennis players of 17–20 years old.
3. To estimate the efficiency of the developed program for development of coordination abilities of tennis players in the process of their training as well as for independent training sessions.

Research methods: theoretical analysis and synthesis of information sources, sociological methods (questioning), pedagogical observation, educational experiment, pedagogical testing, methods of mathematical statistics.

1 Literature review

1.1 Physiological mechanisms of development of athletes' coordination abilities

The Sports Dictionary defines coordination as: «movement is easily stretched, not rigid, all parts of the body correctly, without excessive movement». It can be seen that the definition of coordination in the Sports Dictionary mainly emphasizes the smoothness of body movements.

Some Chinese athletic training experts focus on understanding the ability of athletic coordination, mainly on its effectiveness. They have defined athletic coordination as the ability to make movements.

The Soviet scientist V. H. Platonov from the former Soviet Union pointed out in «Theory and Methodology of Sports Training» that coordination is the ability of people to be fast, intelligent, flexible and labor-saving, that is, the ability to perform tasks in the best way, especially for complex and sudden tasks. German scientist Manfred Grosser believes that coordination is a complex manifestation of various human abilities, mainly including flexibility, learning ability, spatial orientation ability, reaction ability, rhythm, balance, accuracy and other elements.

In our opinion, the ability to coordinate should be that the muscles of each part of the body are under the control of the nervous system, so that the different parts of the body can interact well in time and space to perform technical movements without change.

Action is a form of coordination. It is the basis of internal communication between the environment in the body and the various organ systems. It is the result of the intelligent coordination of nerves, muscles, and perception in the process of action. In short, it is nerves, muscles, and sensation. It is the result of intelligent coordination and coherence of perceptions.

Neural coordination is the coordination of nerve processes that leads in specific conditions to the solution of a motor task by controlling movements through muscle tension. The main way the nervous system coordinates is through coordinated reflex activity. Coordinated reflex activity manifests itself in the process of performing actions by the body. Different muscle groups and different organ systems exhibit simultaneous or sequential coordination, and different effectors respond in an orderly manner. The various activities of the body are performed under the direct or indirect control of the nervous system. Consequently, the more complex the perfect action, the more precise the coordination of the processes of excitation and inhibition of the cortex of the large hemispheres and the more complex the requirements.

Muscular coordination refers to reasonable and proper muscle tension. It is the magnitude, speed, and order of tension of the muscle groups involved in the work in time and space. Muscle coordination is regulated by the nervous system. Muscle coordination is also closely related to the structure of the muscle itself, the composition of the muscle, and the adaptability of the various receptors in the muscle. To coordinate muscle function, specialized and targeted training over a long period of time is required to transform the internal structure of the muscle and improve the adaptability of the body's proprioreceptors.

Perception is the production of nerve impulses by the sense organs, which pass through afferent nerves into the cerebral cortex and then cause the corresponding perceptual sensation. Perceptual coordination involves coordination of internal receptors and coordination of external receptors. The information provided by the various receptors determines the quality of perception. Visual coordination is primarily eye-muscle coordination, which can be used to accurately assess spatial position, distance, and movement of athletes during exercise. At the same time, visual coordination can maintain body balance. Auditory coordination is reflected in the analysis of auditory information and the stability of the vestibular receptors. The better the stability of the vestibular receptors, the smoother the completion of the action. The proprioreceptor is used to determine the degree of joint stretching and reduction , and contraction of muscles. Coordination of proprioreceptor reflex activity is proprioreceptor coordination.

Thus, regardless of the complexity of the action, the completion of each action requires different receptors to transform the stimulation of the internal and external environment into nerve impulses that are transmitted to the cerebral cortex through afferent nerves, and the excitation and inhibition produced by the cerebral cortex are transformed into each other. Dominate and mobilize intelligent and orderly muscle tension so that the body produces regular reactions.

The elements of coordination ability were first summarized in a book by the German scientist Manfred Grosser. He believed that coordination includes spatial orientation ability, reaction ability, learning ability, flexibility, balance, rhythm, accuracy, etc. The scientist L. N. Matveev also agreed with the point of view in «Theory and Methods of Sports» that «the ability to coordinate movements depends to some extent on spatial and muscular sensations, and includes bringing the spatial, temporal and dynamic parameters of action to an exact scale. Requirements and the ability to regulate them». TianMaijiu, a renowned Chinese scholar, believes that coordination capabilities include response capabilities, temporal and spatial perception capabilities, adaptive regulation capabilities, and joint mobilization capabilities. There are also some studies that put forward different constitutive elements according to the specific problems they study. For example, Chinese scholar Chen Xiaoping divided the different sub-capabilities of sports coordination ability and the division of the structure of sports coordination ability by researchers combined with special projects. The components of coordination ability mentioned in various studies include reaction, rhythm, balance, spatial orientation, flexibility, accuracy, learning ability, adaptive adaptation ability, mobilization coordination ability, movement direction, movement perception ability.

Among them, the five elements of proprioception, spatial orientation, reaction, rhythm, and balance are most frequently mentioned. These five elements make up the basic structure of coordination abilities. When a person develops different motor skills, the degree of involvement of these five elements may vary, but it should be the five components of proprioceptive ability, spatial orientation ability, reaction ability, balance and rhythm that play an organic role and the ability to coordinate represents the integration of these five elements.

Charles Bell was the first to define proprioception as the basis of movement and sensory perception. Roland (1977) defined proprioception as the sensation of passive and active body movement. More and more scientists are now viewing proprioception as a specific variable for measuring the perception of muscle movement and the perception of joint position. Improving proprioception can contribute to the formation of motor skills.

Spatial orientation ability refers to people's knowledge of their position, posture, and movement in space. Vision predominates in people's spatial orientation activities, and the information received from vision, hearing and proprioception is processed by the brain. The basis and prerequisite for athletes' mastery of sports technology is their ability to react. Reaction time is the time it takes for the body to clearly respond after stimulation. It is an important indicator reflecting an athlete's ability to react, as well as a benchmark for early selection of the athlete. Reaction time is divided into simple reaction time and complex reaction time. Simple reaction time refers to giving subjects a simple stimulus and they can take action immediately. Complex response refers to the appearance of several possible stimuli, and the athlete must select the desired response as the signal of the various responses.

In competitive sports, rhythm ability is a very important ability that often influences movement learning and movement performance. Rhythm ability can be reflected in the rhythmic performance of some athletic activities, so action rhythm is often used in assessing rhythm ability. Action rhythm refers to the temporal characteristics during action performance, including factors such as amount of effort, duration of time interval, amplitude of action, and speed of action.

The ability to balance refers to the body's ability to coordinate different stimuli from different receptors and vision. It is a basic prerequisite for human body movement, maintaining posture and performing technical movements accurately. The ability to balance includes the two states of static balance and dynamic balance. Whether it is dynamic balance or static balance, it is controlled and realized by the various organs of the human body that control balance. The goal is to keep the body posture stable and make the body better.

1.2 Factors affecting the development of coordination abilities

Coordination training is influenced by many factors. Chinese scientist ZhangKe pointed out through testing the structural equation model that movement coordination ability consists of six abilities: motor cognition, spatial orientation, reaction, proprioception, rhythm and balance. Factors affecting athletic coordination ability are believed to be mainly intrinsic factors such as mechanism level and structural level. In addition, direct conditional factors in conditional factors also influence athletic coordination. The impact on movement coordination and the ability to coordinate movements varies according to the influence of different factors at the three levels of mechanisms, structure and conditionality. Chinese scientist Wang Tang believes that the main factors affecting human body coordination are the external environment and heredity. When the human body learns a certain movement, if it masters it, it can smoothly complete its technical movement. If you learn more complex movements, your body will be affected, and your coordination may also be corrected. By constantly correcting people's physical form, the body acquires more advanced motor skills, and there is a difference between neuromodulation and suppression of cortical excitability. Chinese scientists Yuan Shengming and Wu Jian noted that coordinated development has become a pressing issue in the education of children. Coordination is not only related to genetic factors, but also to qualities such as muscle strength and muscular endurance, speed and speed endurance, body balance, muscle relaxation and contraction, body flexibility and dexterity. Chinese scientist Liu Guanyi believes that the main factors influencing adolescent coordination are training content, internal environment and innate genetics, and external environment.

American scientist Gagne believes that motor skills are the ability to coordinate movements. Stronger motor skills of the body are mainly reflected in the coordination and interaction of the body when performing technical movements, as well as in the quick and intelligent performance of motor tasks. Korean scientists 이준희, 김옥자, 조영희 believe that coordination training is specifically designed to improve flexibility, agility, balance and speed, which are necessary for rapid changes in body movements.

Based on the comparison of domestic and foreign studies affecting coordination training, at the same time sort and investigate the factors affecting the coordination of athletes. In addition to age, gender, height and weight, factors affecting coordination training are also closely related to acquired training. The level of movement coordination varies with age, and coordination training should be emphasized from an early age. The focus should be on developing the coordination of movements of adolescents and children under the age of 10. Conducting coordination training on a scientific basis can improve and develop athletes' coordination and achieve excellent athletic performance.

1.3 Influence of the development of coordination abilities in different sports on the formation of physical qualities

Tennis, volleyball, table tennis and badminton are pure antagonistic sports, and pure antagonistic sports share common characteristics. A study by Chinese scientists Liu Yonglong and Mu Xinling showed that coordination is one of the essential sports qualities of volleyball players. Coordination is essential in the technical movements of volleyball. Only with good coordination can athletes perform more specialized skills. A study by the Chinese scientist Yin Haiyan showed that the main reason influencing the special technical level of badminton players is their own coordination ability, which can perfectly combine body coordination and flexibility with various physical qualities, which helps to improve special performance. Badminton requires coordination with body height. It is very important to coordinate the use of different body links and muscles during the game. The Chinese scholar Yang Qing put forward the idea of giving importance to the ability to coordinate when teaching table tennis. Because the skills and tactics of this exercise are complex and change rapidly, athletes often need to perform a series of technical and tactical movements in a short period of time so that all body parts can be coordinated. Collaboration, this places high demands on body coordination. The study combines pedagogical practice and proposes to actively develop coordination training in table tennis instruction, which provides the basis for future teaching reform and practice.

Chinese scientist Liu Feng came to the conclusion through experimental comparison: adding coordination training to training is significantly better than the control group in improving the ability of right and left strokes, and the content of coordination training method is relatively simple, and it is easy to apply it in daily courses. Chinese scientists Wang Zheng Cheng Peipeng believe that strengthening coordination training during training can increase the interest and enthusiasm of novice tennis players and enrich the training content. Through research, it can be seen that the experimental group joins the game training of coordination and accuracy of strokes. It has been improved and the skill level of novice tennis players in alternating right and left strokes to catch multiple balls has also improved significantly.

According to LTA (1995), the technical action of the serve is a complete coordination chain. From the bending of the knee to the extension of the legs with the movement of the lower extremities, the force of impact is transferred from the stock of the lower extremities to the upper extremities. Only by mastering the order of coordinated force from stock to delivery can technical service actions be more standardized to complete and achieve the best service effect. The results of several experiments show that kinesthetic differentiation and reaction time are important factors affecting tennis coordination abilities. Two-way analysis of variance with repeated measures shows that there are significant differences between the two groups. Coordination training techniques have a positive effect on the performance of young tennis players.

Research on these sports may provide a better guide for coordination training in tennis. Most studies believe that coordinated training promotes the mastery of athletes' basic skills, allows athletes to learn new techniques more quickly, can enhance their performance in specialty sports, and plays an important role in teaching technical movements. Good coordination can positively and effectively improve the competitiveness of athletes. Only athletes with good physical coordination can learn certain skills quickly in a short amount of time, can develop action stereotypes and muscle memory quickly, and can move forward quickly. Adjust skills and tactics so that they can perform consistently and maintain a positive mental attitude. Consequently, athletes' level of play and performance are closely related to the quality of their own coordination. In the game, athletes must be both thick and thin and must react quickly to various emergencies on the court. However, most shots are taken in an unbalanced state, and only well-coordinated athletes can perform at the best level of competition. Increase the proportion of coordination drills in daily drills, and the content of coordination drills should be combined with special elements. It is further explained that tennis places high demands on the quality and coordination of athletes.

1.4 Competitive Characteristics of Tennis

After reading the literature to understand previous scholars who have studied the characteristics of tennis, different scholars give different descriptions: FengLianshi and other scholars believe that tennis is a beautiful action, complex and variable techniques and tactics, fierce confrontation, high physical level. requirements of the antagonistic project. The Chinese scholar Tao Zhixiang believes that tennis is an activity with equal emphasis on technique, tactics and physical fitness. Wang Baocheng, a Chinese scholar, believes that tennis is a sport consisting of many short periods of intense exercise and rest.

The competitive characteristics of tennis are mainly manifested in: a long exercise consisting of a short period of high-intensity exertion and a short period of intermittent exertion requiring high explosive power; it is a combination of several action structures and a special medium. That is, the racket is used to perform the action, and the technical and tactical level of the athlete is reflected through the use and understanding of time and space. Judging by relevant statistics, high-level male tennis players have an average hitting speed of more than 80 kilometers per hour, and the maximum serving speed can exceed 200 kilometers per hour. In high-level play, the game can often last up to 3 hours. Athletes swing more than 300 times, and the interval between each shot is only about 5 seconds. What's more, there will be more than a dozen return trips every minute. This requires athletes to constantly and quickly react to the ball during the game, including quick starts, emergency stops, balance and explosive power. Consequently, athletes need a balanced development of physical fitness, and body coordination is a major component of physical fitness.

Thus, tennis has the characteristics of fast ball speed, multiple changes, long competition times, high intensity, alternation of aerobic and anaerobic exercise. Consequently, in the case of the same technical level, the level of physical fitness has become key in determining the outcome of the game.

1.5 Ways to develop coordination abilities of tennis players

As a means of developing athletes' coordination abilities, in principle, general training and special training should be combined. As practice gradually becomes accustomed, the typical form of motor coordination becomes more and more consolidated, so it no longer has any effect on improving coordination abilities. To maintain the training effect, the exercise should be constantly changed to increase the complexity of the training. By mastering the coordinated exercises of these movements, athletes have improved their coordination and physical performance. Nowadays, this situation is not always seen in competitive sports and often requires constant training based on the small circle that one is used to practicing. As a result, quality skills that are constantly being strengthened have become, against their wishes, insurmountable «coordination barriers» that limit the prospects for perfect competition.

In most cases, this route can be broken down into three ways: first, change the movement technique used, increasing the complexity of movement coordination; second, combine unfamiliar movements with familiar ones; third, actively use external conditions to change the existing pattern of action. For example, using an unfamiliar pose for practice; based on previous practice, use an unfamiliar hand to bounce and kick the ball.

Conclusions. Regardless of the complexity of the action, the completion of each action requires different receptors to convert internal and external stimulation into nerve impulses that are transmitted to the cerebral cortex through afferent nerves, and the excitation and inhibition produced by the cerebral cortex are transformed into each other. Dominate and mobilize intelligent and orderly muscle tension so that the body produces regular reactions.

Tennis has the characteristics of fast ball speed, many changes, long competition times, high intensity, alternating aerobic and anaerobic exercise. Consequently, in the case of the same technical level, the level of physical fitness has become key in determining the outcome of the game.

Thus, the problem of tennis players' coordination ability development is relevant, because improving their coordination abilities will contribute to the improvement of their technique and training effects, as well as provide professional training in the future.

2 Materials and Methods of the Study

2.1 Study design

The study was conducted at the Heilongjiang Lilong Tennis Club in Heilongjiang Province with a sample of 20 novice tennis players. The age of the subjects ranged from 17 to 20 years old. They were randomly distributed into two groups, there was no significant difference in age, height, weight (table 1).

Table 1

Basic information about study participants

Gender	Group	Age	Height (m)	Body weight (kg)
male	experience group	18±0.91	1.70±2.2	55.5±2.66
	control group	18±0.86	1.70±1.95	55.5±3.1
female	experience group	18±1.0	1.62±3.1	49.8±1.1
	control group	18±0.55	1.62±3.3	50±0.9

The experimental group was offered a training method based on the theory of coordination training (coordination ability development program), the control group was given the usual training content and the tennis training course did not add any body coordination training content. The experimental group practiced for 30 minutes according to the established training plan after each tennis training class.

2.2 Questionnaire

In accordance with the research needs of this paper, in order to ensure the scientificity and effectiveness of the experimental test indicators and teaching tools to provide a more sufficient basis for this experiment, experts in the field of tennis instruction at Heilongjiang Universities and Senior Tennis Test Coaches were visited (table 2).

Table 2

List of interview experts (n=8)

Full name	Gender	Occupation	Title	Категория
Li*	female	University Teachers	professor	ITF class I coach
Wang**	male	University Teachers	professor
Li**	male	University Teachers	lecturer	ITF class I coach
Zhang**	female	University Teachers	full-time teacher	ITF class I coach
Fu*	male	Tennis club coach	Intermediate coach
Yu*	male	Tennis club coach	Intermediate coach	ITF class I coach
Xu**	male	Tennis club coach	Senior coach	ITF class Ⅲ coach
He**	male	Tennis fitness coach	Senior coach	ITF class Ⅲ coach

Interview expert questions:

1. How to define the concept of coordination?
2. Is the training method for tennis players coordination suitable?
3. Is the improvement of coordination related to the improvement of tennis specific skills?
4. How to load the coordination training in a training class?
5. What training content do you usually do in the preparation part of tennis training class? Will coordination training be conducted?

2.3 Methods of mathematical statistics

To analyze the data we used generally accepted methods of mathematical statistics. Data processing was performed on a computer using standard programs (Microsoft Exel) and Statistika 10.0.

We calculated:

∑ — sum;

X — arithmetic mean;

S — standard deviation;

S x — mean error of the arithmetic mean;

t — Student's t-test of differences.

The assessment of differences in physical fitness indicators between groups and within groups (Δ) was performed using approximate Student's t-criterion [46].

3 Elaboration of the program of tennis players' coordination ability development

3.1 Opinion of experts on the development of coordination abilities in tennis

Theanalysisoftheanswersofexpertsinthefieldoftennistothequestionsofthedevelopedquestionnaireshowedthatcoordination refers to the correct timing of the body's action of muscle groups, the correct direction and speed of movement, and the balance, stability and rhythm. Among all kinds of physical abilities, coordination training can be said to be the most difficult, because in addition to genetics and athlete’s psychological personality, coordination training is also affected by muscle strength and muscular endurance, technical movement proficiency, the relationship between speed and speed endurance, body center of gravity balance, movement rhythm, muscle relaxation and contraction, and even flexibility.

A method for coordination training for tennis players: overcome unreasonable muscle tension, maintain balance, refine «spatial sense» and spatial accuracy of motion.

Is there a relationship between the improvement of coordination and the improvement of tennis specific skills? Under actual training and competition conditions, various sports coordination abilities are usually not only closely related to each other, but also related to other sports qualities (speed, strength, endurance, flexibility) and various training levels (technical, tactical, psychological) manifested in the interaction. Therefore, if the development of various physical qualities and the improvement of technical, tactical or psychological training levels are achieved through the use of more or less complex motor coordination exercises, then the improvement of various motor coordination abilities will also be achieved. Sync with it.

The load of coordination training in a training session. The training load is arranged according to the training plan of the day. The training day is the main goal of training, the rest day is the main goal of coordination training, and the load is 80 % of the intensity of the training day.

What training content do you usually do in the preparatory part of your tennis training session? Will there be coordination training? Most coaches and physical trainers will carry out a stage of coordination training before training and before the competition. In order to ensure that the coordination of athletes tends to be stable, it is also conducive to improving the efficiency of athletes during training. Most of the training is based on related technical movements, such as muscle strength training, flexibility training, etc.

3.2 Ways to develop and improve coordination abilities of tennis players

1. The development way of overcoming unreasonable muscle tension and the problem of struggling with redundant muscle tension are often associated with the task of improving movement coordination. In addition to the so-called «coordination tension», which is manifested in the insufficient relaxation of muscles or slow transition to relaxation phase after contraction, there are often redundant muscle tension. These tension forms have a negative impact on the overall results of sports movements, hinder the formation of perfect movement techniques, hinder their perfection with the necessary strength and speed, and consume energy due to redundancy. It leads to fatigue ahead of time.

1) Coordination tension. Usually the most obvious performance is in the initial stage of the formation of motor skills. Naturally, the rigidity at the beginning of action is overcome in the process of reasonable teaching. The higher the development of coordination ability, the faster it is overcome. But coordination tension also appears in the completion of the habitual movement, which is sometimes due to fatigue, psychological stress established by the form of stress, such as major competition. The basic way to improve the ability to adjust muscle tension is to systematically complete the corresponding targeted exercises in training.

2) Relax and practice. It is characterized by predetermining the antagonistic state of key alternating muscles and combining the key tension of some muscle groups with the obvious relaxation of others. For example: the follow-up action in tennis. The moment of hitting is the wrist tightening, and then the quick transition to a relaxed swing. But in the process of the game, due to the lack of relaxation, it will lead to the ball out of the net or out of bounds. Therefore, in the practice of eliminating the tension of coordination in the competition, the more sufficient and accurate attention should be paid to the unique movement coordination components of competitive events, the more effective the practice will be. However, no matter how reasonable the training practice selected according to this feature is and how appropriate it is to combine with the most effective muscle tension and relaxation task in competition action, it should be finally solved through competition practice, which is also the «match led training» proposed by tennis recently.

3) Tonic tension. This is the same as coordination tension, which can be reduced under the influence of systematic training. However, some of the athletes who have a certain degree of training also have stubborn congenital hyperstraightness. Due to greater muscle fatigue, all people may have temporary tonic tension. One of the effective ways to reduce tonic tension is to swim or immerse directly in the water (the buoyancy of the water opposes gravity, which increases the tension of muscles involved in maintaining posture). Beneficial also is, in order to eliminate the temporary tonic tension, is specialized warm water bath, sauna and massage.

2. The way to keep balance

In the vast majority of competitive sports, whether the body can keep balance in various postures is the key to complete the action with high quality. At this time, the whole body posture will not be completely static, the so-called static is also in the blink of an eye, but in the process of posture change, if you can maintain balance, that is the so-called «dynamic balance». For example: tennis in the «back» and so on. The improvement of dynamic stability is mainly through the adaptation of motor skills to different external movement conditions. In the process of training, according to the pre-determined, changing the conditions of the training course (such as: the track should be made before the training of tennis clay court, the grassland should be used under bad conditions, etc.), the selection of them should help to expand the scope of the variability of sports skills as far as possible.

3. The way to improve the spatial sense and the spatial accuracy of action

All competitive events with the characteristics of active sports activities require highly developed and correct evaluation of the spatial conditions of action (evaluation of distance, distance to the target, size of the field, etc. when interacting with other athletes) and accurate exertion according to their degree. The solution to improve the «spatial sense» and the spatial accuracy of actions is based on the systematic completion of the tasks with the requirements of improving the accuracy of differentiation in assessing the spatial conditions of actions and controlling the accuracy of actions within the limits of specified spatial parameters. The specific contents, methods and rules of homework in different competitive events, of course, depend on the characteristics of the specific object of competition. In the ball game for the form of changing sports, improve the «sense of space» at the same time to complete the requirements in the direction of attack, time and the use of force are very accurate operation. For example, the backhand «pressure ball» in tennis needs a strong «sense of space». In order to improve the feeling, it is better to use the work of increasing the difficulty step by step, in which the various parameters of «external space» should be changed. For example: tennis practice straight line, diagonal line combination.

In the actual training and competition conditions, the coordination ability of various sports is usually not only in close contact with each other, but also in the interaction with other sports qualities (speed, strength, endurance, flexibility) and all aspects of training level (technology, tactics, Psychology). Therefore, if the development of physical fitness and the improvement of technical, tactical or psychological training level are achieved through more or less use of complex exercise coordination practice, then the improvement of various sports coordination ability will also be synchronized with it. For example: Roger Federer is one of the best players in the world to handle random balls, thanks to his highly coordinated body. Because of this, he can also win his 17th Grand Slam Cup in the world of top tennis after the age of 30. Therefore, improving or enhancing the body coordination ability will directly or indirectly promote the improvement of work saving and endurance, as well as the improvement of sports technology.

When making a training plan to promote the improvement of coordination ability, we must consider the following load components: the complexity of the action, the degree of activity, the duration of a single action, including the number of repetitions and groups, and the interval between exercises.

3.3 Program of development of coordination abilities of tennis players 17–20 years old

Based on the principles of coordination development a program for the development of coordination abilities of tennis players in the process of their training, as well as for independent training sessions (Table 3) was developed.

Table 3

Coordinated training program

practice	Week 1	Week 2	Week 3	Week 4	Week 5	Week 6
Limb class
Day 1	1) Circle your arms in different directions: 10 turns × 3 groups 2) Left and right hands alternately touch the opposite side feet: 5 rounds × 3 groups	1) Knee lift balance: 20 seconds × 3 groups 2) Swallow balance: 15 seconds × 3 groups	1) Rotation jump: left and right 5 turns × 3 groups 2) Forward bend cushion step jump: 10 times × 3 groups	1) Squat: 10 times × 3 groups 2) Lower waist touch ankle:5 times × 3 groups	1) Forward rollover: 10 times × 3 groups	1) Circle your arms in different directions: 10 turns × 3 groups 2) Forward bend cushion step jump: 10 times × 3 groups
Day 2	1) Rotation jump: left and right 5 turns × 3 groups 2) Squat: 10 times × 3 groups	1) Lower waist touch ankle: 5 times × 3 groups 2) Knee lift balance: 20 seconds × 3 groups	1) Left and right hands alternately touch the opposite side feet: 5 rounds × 3 groups 2) Squat: 10 times × 3 groups	1) Forward rollover: 10 times × 3 groups	1) Left and right hands alternately touch the opposite side feet: 5 rounds × 3 groups 2) Squat: 10 times × 3 groups	1) Forward rollover: 10 times × 3 groups
Day 3	1) Forward bend cushion step jump: 10 times × 3 groups 2) Swallow balance: 15 seconds × 3 groups	1) Forward rollover: 10 times × 3 groups	1) Swallow balance: 15 seconds × 3 groups 2) Lower waist touch ankle: 5 times × 3 groups	1) Forward bend cushion step jump: 10 times × 3 groups 2) Knee lift balance: 20 seconds × 3 groups	1) Rotation jump:5 turns left and right × 3 groups 2) Knee lift balance: 20 seconds × 3 groups	1) Forward bend cushion step jump: 10 times × 3 groups 2) Swallow balance: 15 seconds × 3 groups
Walking and running
Day 1	1) Side sliding steps of front and rear swing arms: 30m × 3 groups 2) Waist turn cross step: 30m × 3 groups	1) Oblique jump tennis line: 15m × 3 groups 2) Rope skipping: 100 × 3 groups	1) Oblique jump tennis line: 15m × 3 groups 2) Waist turn cross step: 30m × 3 groups	1) Double arm circling: 30 meters × 3 groups 2) Oblique jump tennis line: 15m × 3 groups	1) Touch the ball and turn back: 3 groups	1) Waist turn cross step: 30m × 3 groups 2) Leg folding run: 30m × 3 groups
Day 2	1) Run backward for 30 meters × 3 groups 2) Leg folding run: 30m × 3 groups	1) One foot side jump 15m × 3 groups 2) Turn back run 3 groups	1) «Bear» climb 10m × 3 groups 2) Run around with your arms 30 meters × 3 groups	1) Backward run30 meters × 3 groups 2) Rope skipping: 100 × 3 groups	1) One foot side jump15m × 3 groups 2) Side sliding steps of front and rear swing arms: 30m × 3 groups	1) Touch the ball and run back 3 groups
Day 3	1) Run 30 meters around the ring with both arms × 3 groups 2) «Bear» climb 10m × 3 groups	1) Leg folding run: 30m × 3 groups 2) Side sliding steps of front and rear swing arms: 30m × 3 groups	1) Touch the ball and turn back: 3 groups	1) Oblique jump tennis line: 15m × 3 groups 2) Leg folding run: 30m × 3 groups	1) «Bear» climbed 10 meters × 3 groups 2) Rope skipping: 100 × 3 groups	1) Oblique jump tennis line: 15m × 3 groups 2) Double arm circling: 30 meters × 3 groups
Comprehensive class
Day 1	1) Vertical and horizontal support jump body: 10 × 3 groups 2) Mobile passing tennis ball 15m × 3 groups	1) Drop ball practice 5 times × 3 groups 2) Non racket hitting 10 balls × 3 groups	1) Mobile passing tennis ball 15m × 3 groups 2) Snake obstacle running 6 balls × 3 groups	1) 5 sets of non overturning balls	1) Snake obstacle running 6 balls × 3 groups 2) Bounce the ball back 10 times from the wall × 3 groups	1) 10 vertical and horizontal support jump bodies × 3 groups 2) Snake obstacle running 6 balls × 3 groups
Day 2	1) Bounce ball from Wall 2) 10 times × Three groups do not overturn the ball tube: three groups	1) Snake obstacle running 6 balls × 3 groups 2) Field «table tennis» 3 points × 3 groups	1) Non dominant hand Stroke 20 balls × 3 groups	1) Play «Golf» once × 3 groups 2) Mobile passing tennis: 15m × 3 groups	1) «Z«ball training 10 times × 3 groups 2) 10 vertical and horizontal support jump bodies × 3 groups	1) Field «table tennis» 3 points × 3 groups 2) Drop ball practice 5 times × 3 groups
Day 3	1) «Z«ball training 10 times × 3 groups 2) Play «Golf» once × 3 groups	1) 5 sets of non overturning balls	1) «Z«ball training 10 times × 3 groups 2) Drop ball practice 5 times × 3 groups	1) Field «table tennis» 3 points × 3 groups 2) Drop ball practice 5 times × 3 groups	1) 5 sets of non overturning balls	1) Non dominant hand Stroke 20 balls × 3 groups

In the process of training, the training of coordination ability should be combined with other abilities, so as to develop the physical quality in an all-round way. 2) The coordination training will be applied to the special, improve the application of coordination in the special skills and tactics, so that teenagers can master the skills faster. 3) Learn to relax your muscles. In the process of an action, some muscles are tense, and some muscles are relaxed. To learn in the process of using the action of constant tension and relaxation alternately, so that the action coordination. 4) The training of motor coordination ability should be combined with the psychological characteristics of teenagers and children. Teenagers and children have their own development characteristics. In this age group, their concentration time is very short. If coaches want to improve efficiency, they should train at the best time of attention, but too much training is not good. At the same time, their mechanical memory ability is strong, coaches can carry out special language and beautiful action demonstration, in order to enhance their impression and improve training efficiency. Psychologically, teenagers and children are emotional and need more encouragement and less criticism from coaches. The best training effect can be achieved by using words that are in line with the physical and mental characteristics of teenagers and children and combining with relatively new teaching methods.

Conclusion. On the basis of principles of development of coordination the program of development of coordination abilities of tennis players of 17–20 years old in the process of their training as well as for independent training sessions was developed. The program is designed for 6 weeks. The experimental group practiced for 30 minutes according to the established training plan aftereach tennis training class.At the beginning or at the end of each training a certain amount of coordination exercises should be arranged. These can help regulate a boring training atmosphere, improve athletes' body coordination and lay the foundation for future technical instruction.

In the daily training of tennis players, body coordination exercises should be combined with various physical activities and technical drills whenever possible to improve coordination and other physical fitness as well as mastery of the game.

4 Evaluation of the effectiveness of the developed program for the development of coordination abilities of tennis players 17–20 years old in the process of their training

4.1 Influence of coordination training on tennis players' quickness

Speed quality refers to the body's ability to complete exercise quickly and the ability to react quickly to changes in the external environment. In tennis, speed is extremely important. Tennis matches are fast in terms of judgment, ball speed, and on-court displacement. Therefore, the requirements for reaction speed, action speed, and movement speed are very prominent. According to the regulations of tennis courts, the running distance of athletes is relatively short, so it is impossible to accelerate to the maximum. In this way, the athlete's top speed is not particularly important. Tennis is faster, and athletes need to move faster to make the best preparation for hitting the ball. Therefore, the ability to accelerate is particularly important for tennis players. According to the characteristics of tennis, a 30-meter run was selected as the test item. After a 20-minute break, another 50-meter test was arranged.

The test location is a plastic track, standing start, hand timer, starter, two persons of the same gender. After 6 weeks of experimental training, it can be seen that the speed performance of the two groups of test players has improved to different degrees.

The test method is the starting point of 100 meters on the standard 400-meter track, and the end points of 30 meters and 50 meters are set, and the 30-meter run and the 50-meter run are respectively performed, and the time spent by the subjects running at this distance is recorded.

Through 6 weeks of training, it can be seen that the speed performance of the two groups of tested athletes has improved to different degrees. Through the comparison before and after 30 meters, it can be seen that the speed increase of the experimental group is particularly significant, with the male players increasing by 0.52±0.17 sand the female players increasing by 0.41±0.11s (table 4, 5). The improvement of the speed performance of the experimental group members is inseparable from the coordination training of 30 minutes each time 3 times a week. In the completed training plan, there are some contents that not only develop the coordination ability of the body, but also improve the speed quality.

Table 4

Comparison of speed quality before and after the 30-meter experiment (male)

	Pre-experiment score (s)	Results after experiment (s)	Change value (s)
test group	5.38±0.19	4.86±0.28*	0.52±0.17*
сontrol group	5.40±0.17	5.12±0.22	0.28±0.12

Note: * — p<0.05 when comparing similar indicators of the control and experimental groups.

Table 5

Speed quality before and after the 30-meter experiment (female)

	Pre-experiment score (s)	Results after experiment (s)	Change value (s)
test group	5.82±0.39	5.41±0.39	0.41±0.11*
сontrol group	5.75±0.13	5.58±0.16	0.17±0.06

Note: * — p<0.05 when comparing similar indicators of the control and experimental groups.

Through the comparison between the 50-meter test groups, it can be seen that the speed increase of the experimental group is particularly significant, and the distance of 50 meters can better give play to the speed advantage of the experimental group members. Although the speed performance of the players in the control group improved, it was not obvious. The performance improvement was related to the improvement of their physical function through 6 weeks of tennis training without participating in any sports before, thereby improving the speed quality (table 6, 7).

Table 6

Speed quality before and after the 50-meter test (male)

	Pre-experiment score (s)	Results after experiment (s)	Change value (s)
test group	8.51±0.16	7.96±0.26*	0.55±0.16*
сontrol group	8.48±0.15	8.23±0.23	0.25±0.11

Note: * — p<0.05 when comparing similar indicators of the control and experimental groups.

Table 7

Speed quality before and after the 50-meter test (female)

	Pre-experiment score (s)	Results after experiment (s)	Change value (s)
test group	9.52±0.36	9.01±0.37*	0.51±0.13*
сontrol group	9.65±0.15	9.38±0.17	0.27±0.07

Note: * — p<0.05 when comparing similar indicators of the control and experimental groups.

The above four sets of data show that the coordination ability is good or bad, which has a greater impact on speed. The improvement of speed performance by coordination training is greater than that of ordinary tennis skills and tactics training alone. The three categories of speed quality are also closely related to the physiological mechanism of coordination. Response speed is the ability of the human body to respond quickly to external environmental stimuli, and is determined by the conduction speed of nerve reflexes. Neural coordination is the coordination of nerve excitement and inhibition when completing the action. Both use nerve conduction to complete the action. Movement speed and movement speed are both during exercise, through the coordination of muscles to maximize the abilities of the two. Muscle coordination refers to the proper and reasonable exertion of muscles during exercise. During exercise, the coordination, proper and reasonable force of the muscles are also what the two have in common. Due to the complexity of the tennis event, reaction speed, action speed, and movement speed are indispensable in the event. The reaction speed determines the ability to start, and all random balls have the highest requirements for the reaction speed. Movement speed determines the ability to swing, and the ability to move speed determines the offensive ability and defensive range. Therefore, good coordination is directly proportional to the increase in speed.

4.2 Effects of coordination training on tennis players' technique

Tennis is one of the stricter requirements for various physical fitness and physical functions among many net-net competition events. Due to the reasons of serving and high-pressure balls, the two techniques of being too short are subject to certain restrictions. At the same time, athletes have to run in a wide range; even forward rushing to save a low bouncing ball, too high height will also be restricted in some respects. And excellent body coordination can make up for shortcomings in height. However, no matter how fast the speed, the strength, and the coordination ability are, if there is no good tennis technique and tactics as the premise, these excellent physical qualities are useless. French star Tsonga is one example. Therefore, the excellent innate and acquired physical fitness must be applied to tennis skills and tactics. The mastery and constant update of tennis skills require excellent physical fitness as a guarantee. When the physical fitness reaches a stable state, the role of coordination is particularly important. Tennis technical movements are completed in control and countermeasures, which requires athletes to have good muscle feeling and control ability, and coordination ability is to improve Muscle sensation and control are important factors, so coordinated tennis technique plays a pivotal role.

The experiment on the impact of coordination on technique is conducted by the coaches' technique of scoring the students' hitting movements. The coaches invited do not know which one is the experimental group and the control group. Since the students in the two groups have no basic tennis skills, the forehand and backhand swing techniques were explained and demonstrated in the tennis class the day before the technical evaluation. At the beginning of the technical evaluation, the two groups of trainees did forehand and backhand swing exercises at the same time. The coaches scored according to the players' forehand and backhand technical movements, with a full score of 100. A single action has a full score of 10 points, a single item with a score of 6 (inclusive) or more is a pass, a score of 7 (inclusive) or more is a medium, a single action with a score of 8 (inclusive) or more is good, and a single item with a score of 6 (inclusive) or more is excellent.

Preparatory action: 1) Whether the upper body leans forward. 2) Whether the center of gravity is lowered and falls on the forefoot. Introducing stage: 3) Whether the introductory action is calm and soft. 4) Whether the upper body leans forward and the center of gravity is lowered. Swing stage: 5) Whether the center of gravity rises slowly with the swing of the racket head. 6) Whether the power sequence of pushing the ground, turning the waist, turning the shoulder strap and swinging the pat is achieved. Follow-up stage: 7) Whether the center of gravity is fully shifted. 8) Whether the racket is gently carried on the shoulder. Swing while moving: 9) Whether the pace is easy and comfortable.10) Whether the pace and swing are smoothly connected.

After the end of the experimental period, forehand and backhand technical evaluation were performed on the two groups respectively. The format is to perform the swing technique evaluation first and then the coaches send multiple balls across the net. Each player hits 10 balls for each forehand and backhand, and the two groups of players do it at the same time. After the technical evaluation is over, the service teaching will be conducted. While the trainees are learning the service skills, the coach will score on-site according to the situation of the two groups of players, and then conduct the service technical evaluation according to the following positions: 1) Whether the tossing ball is stable 2) Whether the hip extension is obvious 3) Whether the trajectory of the stroke and swing is correct, coherent and natural. 4) The whole set of serve has a high degree of technical continuity. Finally, it should be taken the average of the coach’s technical scores as the athlete’s technical score.

This experiment did not carry out male and female groups. In actual teaching, the female students at this stage are not inferior to the male students in their striking power and movement speed, and their skills and physical coordination are not inferior to the male students, and even more so than the male students. In the experimental group, after 6 weeks of coordinated practice, the scores of forehand and backhand swing skills were 75.00±3.59 before the experiment and 89.80±2.21 after the experiment increased by 14.8±3.21 points, which was significantly improved (р<0.05) (table 8).

Table 8

Comparison of forehand and backhand technique before and after experiment (male and female)

	Pre-experimentresults	Post-experiment results	Difference	Combine the ball	Difference
test group	75.00±3.59	89.8±2.21*	14.8±3.21*	84.57±2.35*	9.57±2.32*
сontrol group	75.40±2.55	87.60±2.73	12.2±2.71	79.35±1.84	3.95±2.61

Note: * — p<0.05 when comparing similar indicators of the control and experimental groups.

The increase in the number of technical scores indicates that during these 6 weeks there is a further mastery of technical movements and an improvement in physical coordination, especially with the deepening of coordination exercises, when learning backhands and combining the ball, the body. The improvement of coordination ability is particularly prominent in the mastery of technology. For example: Master the movement faster and hit the ball more accurately. The control group increased from 75.40±2.55 before the experiment to 87.60±2.73 after 6 weeks of practice. There was also a significant improvement, more of the improvement in technical proficiency. After 3 weeks, the learning backhand and combined ball practice will be combined with the initial learning forehand combined ball. There is no difference in technical mastery. In terms of combined ball skill scores, the experimental group and the control group have lower technical evaluation scores than after the test because the combined ball practice is far more difficult than the empty-handed swing practice. The combined ball scores of the experimental group are compared with the experimental group’s 84.57±2.35. It was significantly higher than the control group 79.35±1.84. Coordination exercises significantly improved the combined ball practice scores (р<0.05).

The technical evaluation of the serve is carried out after 6 weeks. The experimental group passed 6 weeks of coordinated training, and the technical evaluation scores all reached 75 points or more, while the control group's mastery of the new technology was far worse than the experimental group, only an average score of 65.32. It shows that through coordination training, it is of great help to master new technology in the early stage of learning new technology (table 9).

Table 9

Technical Evaluation Results Comparison of Serve Technical Evaluation (Male and Female)

	Technical evaluation results (s)
test group	76.46±2.12*
сontrol group	65.32±1.21

Note: * — p<0.05 when comparing similar indicators of the control and experimental groups.

Judging from the above data and the coach’s feedback information, the improvement in technical performance of the experimental group after coordination training is generally higher than that of the control group. Therefore, the improvement of coordination ability is important for mastering tennis skills (especially in the early stage of learning new technology). Improvement has played a good role in promoting.

Conclusions. The developed program of development of coordination abilities is effective as it promoted improvement of technical indicators of tennis players of 17–20 years old, and also increase of level of their speed abilities.

Conclusion

The results of the performed work allowed to expand the ideas about the development of coordination abilities, as well as to experimentally justify the effectiveness of the developed program of development of coordination abilities of tennis players in the process of training and allowed to make the following conclusions.

1. Regardless of the complexity of the action, the completion of each action requires different receptors to convert internal and external stimulation into nerve impulses that are transmitted to the cerebral cortex through afferent nerves, and the excitation and inhibition produced by the cerebral cortex are transformed into each other. Dominate and mobilize intelligent and orderly muscle tension so that the body produces regular reactions.

Tennis has the characteristics of fast ball speed, many changes, long competition times, high intensity, alternating aerobic and anaerobic exercise. Consequently, in the case of the same technical level, the level of physical fitness has become key in determining the outcome of the game.

Thus, the problem of tennis players' coordination ability development is relevant, because improving their coordination abilities will contribute to the improvement of their technique and training effects, as well as provide professional training in the future.

2. On the basis of principles of development of coordination the program of development of coordination abilities of tennis players of 17–20 years old in the process of their training as well as for independent training sessions was developed. The program is designed for 6 weeks. The experimental group practiced for 30 minutes according to the established training plan after each tennis training class.At the beginning or at the end of each training a certain amount of coordination exercises should be arranged. These can help regulate a boring training atmosphere, improve athletes' body coordination and lay the foundation for future technical instruction.

In the daily training of tennis players, body coordination exercises should be combined with various physical activities and technical drills whenever possible to improve coordination and other physical fitness as well as mastery of the game.

3. The developed program of development of coordination abilities is effective as it promoted improvement of technical indicators of tennis players of 17–20 years old, and also increase of level of their speed abilities.

Research suggestions:

A) Every tennis club should pay attention to more than just tennis skills and competition results during the training period. A certain amount of coordination exercises should be arranged at the beginning or end of each training session. This can fine-tune the boring atmosphere of practice, improve athletes' body coordination, and lay the foundation for future technical instruction.

B) In the daily training of tennis players, body coordination exercises should be combined with various physical activities and technical exercises whenever possible to improve coordination abilities and other physical fitness as well as mastery of the game, technical movements.

C) Pay attention to the placement of physical activities when conducting coordination training. Therefore, it is advisable to pay attention to the ability to coordinate between the different limbs of the body when performing coordination training and not to increase the intensity of training to achieve too much training effect, which leads to the training effect of extreme things.

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