Physical Factors and Developmental Foundations [2], [4], [5], [15], [22]

Pay attention to the indicators that are less affected by genetic factors. In essence, model evaluation is the assessment of current value. Therefore, not all morphological and functional indicators have characteristics for the model, but only those indicators that have changed through systematic training have that value.

Testing morphological indicators (by anthropometric methods) when building an athlete's model is often not as important as when initially selecting. However, this is still necessary, especially for athletes. The test results will show whether the athlete's body develops according to general rules or not, and whether it meets the specific requirements of the athlete's specialized sport or not.

1.4.2. Factors related to physiological functions

Badminton is a racquet sport played by two or four players, with a time structure characterized by short, high-intensity actions. The sport has five events: men's singles, women's singles, men's doubles, women's doubles, and mixed doubles, and each event requires technical preparation, control, and fitness. A typical badminton match is a 7-second rally with a 15-second rest period, with an effective play time of 31%. The sport is highly skilled and effortful, with an average heart rate (HR) above 90% of the athlete's maximum HR. The intermittent actions during a match require the use of both the aerobic and anaerobic systems: 60–70% for the aerobic system and about 30% for the anaerobic system, with a greater demand on alactic metabolism over anaerobic lactic metabolism. The shuttlecock trajectory is unstable and athletes perform specific moves such as jumping and jumping, powerful shots using a specific movement pattern. Finally, badminton players have the appropriate visual ability to collect accurate visual information in a short period of time.

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During a match, the athlete needs to maintain a high intensity of play for as long as possible. Energy expenditure depends on the athlete's morphological factors and the efficiency of movement. The athlete focuses on the ball and the opponent in order to predict the movement of the ball and the opponent. Due to the preparation of the attack and the unstable and unpredictable trajectory of the ball, hitting the ball the full length of the court requires a high level of skill [55, 81]. The athlete adjusts his movements using efficient biomechanical factors to respond to the amount of visual information gathered. This requires rapid changes in direction, jumping, rapid movement towards the net, and rapid arm movements from various positions [96, 74]. These factors influence the physical demands.

Under the influence of the amount of functional movement of all organs and organ systems in the body, there are changes in certain directions to adapt to stimuli.

Physiological characteristics of 18-22 age group.

- Nervous system: At the age of 18-22, the nervous system continues to develop slowly and reaches perfection, the ability to think analytically, synthesize, and abstractly develops, facilitating the formation of conditioned reflexes. The total volume of the cerebral cortex does not increase much, but the internal structure of the cerebral cortex is more complex. The ability of the athlete to work mentally during training changes over time and is expressed through changes in the stages: Adaptation - stability

- increase - decrease. The rational use of physical education means to practice in combination with rest and relaxation will improve working capacity. Motor activities as well as all other behaviors are controlled by the nervous and humoral systems, in which the nervous control occupies the dominant position.

- Locomotor system: Bones begin to slow down their growth rate, the cartilage at the ends of the bones has ossified, and the spine stabilizes its shape. Bones that are regularly subjected to large mechanical impacts are rich in inorganic substances, so the femur, especially the tibia, is harder than the humerus. Body height also depends on genetic factors, so in the selection process we must always pay attention to this important factor.

- Circulatory system: The circulatory system of athletes aged 12-18 is developing and perfecting. During a person's life, the pulse rate is not the same. At a young age, the heart beats relatively fast, at the age of 18-20, the heart rate begins to stabilize: 70-80 times/minute for men and 75-85 times/minute for women. The pulse is created by the activity of the heart. The pulse rate is equal to the frequency of heart contractions. The pulse rate index at rest will change a lot under the influence of physical exercise. The pulse measurement method is simple, easy to do and provides very reliable information about the functioning of the circulatory system and also the health status of the body in working life as well as sports activities.

Blood pressure: Is the pressure of blood pressing on the walls of blood vessels created by the pressure of the heart. Normally, maximum blood pressure is from 100 - 130 mmHg; below 100 mmHg is low blood pressure, above 130 mmHg is high blood pressure. Minimum blood pressure from 65 - 85 mmHg is average. Blood pressure index usually depends on age and gender. Blood pressure index is a relatively stable index, blood pressure changes little during exercise.

- Respiratory system: At the age of 18 - 22, children's respiratory system is relatively fully developed, respiratory muscles are strongly developed, the regulation of the central nervous system for breathing is stable and rhythmic. In physical activities, the amount of lung ventilation increases gradually according to the activity capacity. Activities at low capacity, lung ventilation increases mainly

increased air circulation. When working at increasing capacity, the respiratory rate increases in parallel with lung ventilation, and air circulation increases close to the limit of vital capacity. To determine vital capacity, a spirometer is used. Adolescents have a respiratory rate of about 10 - 12 times/minute. This is a relatively favorable age for the development of respiratory function [2], [37].

1.4.3. Physical factors and development foundations [2], [4], [5], [15], [22]

Physical training occupies an important place in the training of badminton players. The rapid development of quickness, strength - speed and technical endurance of badminton players plays a huge role in achieving high results.

In sports practice, the selection of badminton players is often based on the results of professional tests. According to the research results of experts, the physical development of badminton players does not occur evenly. The strongest development of physical qualities occurs in the first 1.5 years of training. This trend is especially evident in speed qualities. After 1.5 years of training, the order of physical quality development is as follows: quickness, professional endurance, strength, strength - speed.

1.4.3.1. Physiological basis of speed training [2]:

In sports activities, speed is one of the indispensable qualities. In general, speed is the ability to move quickly and has the following manifestations:

- Latency time of motor response.

- Single action speed.

- Frequency of movement.

In practice, quick strength activities are often expressed in a comprehensive way, the connection of movements and coordination of movements are always closely and logically connected to each other.

Movement speed is one of the determining factors in many sports. The physical basis for the ability to perform individual movements quickly is rapid power capacity and speed capacity.

Factors affecting the speed of the power are the flexibility of the nervous process, that is, it depends on the speed of the rotation between the state of excitement and inhibition of the motor center, the content of ATP under the influence of nerve impulses, as well as the speed of its resynthesis. The process of synthesizing ATP (Adenosine Triphosphate) is almost carried out by anaerobic mechanism. The energy of human power activity has the specific nature of transferring power directly, all have the same structure.

1.4.3.2. Physiological basis of endurance training [2].

Endurance is the ability to perform a given activity, or the ability to persevere, the ability to move for the longest period of time that the body can endure during activity.

Endurance ensures that athletes maintain the best intensity during long periods of competition, corresponding to their training ability, while also ensuring high quality movements and good technical behavior. Therefore, endurance is not only a factor that determines and affects competition performance, but also a factor that determines training performance and endurance of athletes.

Endurance in badminton is the ability to maintain activity for a long time and with great intensity. Badminton competition activities are calculated by rounds with no fixed time. On average, a round lasts from 15 to 30 minutes, the time of each round and each match depends a lot on the overall level of both sides. A match between two opponents of high and equal level, if having to play all three rounds, can last up to 90 minutes. Along with the long playing time and the situation of each match. This requires each athlete

a high level of physical preparation and especially professional endurance to be able to maintain long-term competition through each match and throughout the tournament.

Endurance in badminton is demonstrated in the maintenance of the activity of most organs in the body. It is the continuous coordination of the activities of the hands and feet in the movements of moving, jumping, hitting the shuttlecock and then moving, jumping, hitting the shuttlecock... it is the maintenance of long-term activity of the nervous system through the activities of judging and handling situations of hitting the shuttlecock to ensure the highest efficiency of each technical performance. This requires comprehensive development and maintenance of a high level of operational capacity of the body's energy supply system for each athlete.

Endurance in badminton is expressed as strong endurance and fast endurance.

As analyzed in the speed and strength training, the characteristics of the movements shown in badminton in any situation require speed and strength of the movements. During the competition, athletes are not only allowed to perform a few moves, jumps or hits, but these techniques are performed continuously and maintained at high intensity throughout the match. The decrease in strength and speed during the competition shows that the athlete's endurance is still low and this will inevitably lead to low performance.

1.4.3.3. Physiological basis of strength training[2]:

Strength is one of the important qualities of human beings, it is the ability to overcome external resistance with the support of muscles. The appearance of strength depends on the state of the nervous system in accordance with the activities of the cerebral cortex and the physiological cross-section of the muscles, the biochemical changes of the muscles, the changes in muscle excitement, the level of muscle fatigue, and human posture and many other causes...

Maximal strength is the greatest strength produced by the ability of the neuromuscular system when the muscles contract and stretch at will to the greatest extent.

Fast strength (also known as speed strength) is the neuromuscular ability to overcome the opposing force of large muscle contraction and extension speeds, the ability of fast muscle fibers to function for long periods of time.

Endurance strength is the ability of the body to resist fatigue during prolonged strength exercise. Different sports should set different requirements for strength qualities. In sports activities, strength is always related to other physical qualities such as speed and endurance. For these reasons, it is necessary to determine the requirements for strength capacity according to the characteristics of the sport. Maximum strength capacity has a high value for the achievements of the sports: shot put, javelin throw, chain weight...

Speed ​​power is especially important for improving performance in running, jumping, and even throwing and middle-distance running. Speed ​​power has the effect of perfecting the ability to perform quick movements, speed power determines performance in cyclic sports. Endurance requires overcoming great resistance over a long period of time.

There are two forms of strength training:

- Form of corrective movement.

- Form of concession movement.

- Corrective movement form: this form of movement, internal force can overcome external force at the fastest speed corresponding to the magnitude of the selected resistance force and the purpose of the strength training session. The corrective movement form is especially suitable for strength training of sports with advantages in the mode of corrective activity of the neuromuscular system, in which the force-time progression needs to be widely suitable for the requirements and tasks of professional competition.

- Concessional form of movement: in maximal strength training, external force can be more than 100% of the speed strength capacity. This excess force effect occurs when the highest internal force is used, in which the maximum contraction intensities are required for the entire range of motion. In addition, and small movement speeds are suitable in maximal strength training, so in this form it is necessary to ensure a maximum movement intensity during the optimal contraction time.

The characteristic of badminton competition is that athletes must always move continuously at high speed within the area of ​​their court by running or jumping, along with combining reasonable, fast, and strong hitting movements to carry out their tactical intentions in the competition to achieve high efficiency. Therefore, strength in badminton is often demonstrated in starting movements (from the preparation position to move to the hitting position), jumping movements, the ability to move quickly and hitting movements that require maximum force of the body such as smashing the shuttlecock.

An important requirement when using strength in badminton technical movements is to maximize the effectiveness of that technique and cause unexpected, passive situations for the opponent during the competition. At the same time, it is necessary to maintain that strength throughout the long period of the competition, not only in each match but throughout the course of a tournament.

Power-speed development requires not only an increase in the speed of contraction but also an increase in maximal strength. The significance of this maximal strength for rapid strength capacity depends on the requirements of the performance structure of the sport. In sports where maximal strength is the basis for determining optimal speed of movement, maximal strength training must be combined with rapid strength training.