In school volleyball training, the relationship between flexibility, coordination, sensitivity and ball sense, and the influence of finger and wrist flexibility on passing effect show that flexibility is conducive to preventing injuries, and flexibility is an indispensable physical quality of volleyball players, which is directly proportional to the level of sports skills.

Keywords: traditional sports school; Volleyball; Flexibility; Flexible mass

1, preface

Volleyball is a team event against the net, which is skilled, skillful and comprehensive. Most of the movements are carried out in fierce confrontation. It requires athletes to master fine techniques and be able to change their movement structure quickly, accurately and reasonably with or without support according to sudden changes in the field. As well as the magnitude of the force and the direction of motion, to adapt to these changes. Therefore, athletes are required to have good physical fitness.

2. Research methods

By using the methods of literature, investigation, testing and comparison, some explanatory data are obtained, which proves the importance of flexibility in volleyball.

3. Several factors related to flexibility and volleyball:

Volleyball is a highly technical sport, especially in the rapid development of volleyball today. The exertion of various skills in the competition requires a high degree of control, physical balance and ball control. Therefore, volleyball players must have comprehensive physical fitness to adapt to the current development trend. However, every physical quality in the human body does not exist alone, they complement each other and are closely related.

Flexibility: refers to the ability to expand the range of motion of joints. The expansion of the range of motion joints will accurately control random movements.

3. 1 the relationship between flexibility and coordination

The purpose of training is to develop and consolidate the correct action results, cancel the redundant actions and gradually become coordinated. Flexibility determines the muscle energy state dominated by the nervous system, especially the improvement of coordination between the central nervous systems, which can fully relax the muscles involved in work during muscle activity, thus reducing the obstacles of initiative, ensuring the increase of exercise range and making the movements very coordinated after the formation of motor skills.

3.2 the relationship between flexibility and sensitivity

From the data, we know that the sensitive quality of volleyball players refers to the high manipulation ability to coordinate and accurately complete movements and the ability to quickly change the direction of a certain part of the body under various changing conditions. It is a comprehensive quality, and sensitive movements can only be based on a certain level of strength, speed, flexibility and other qualities.

3.3 the relationship between flexibility and ball feeling

Here, we must first understand: what is the sense of the ball? The so-called sense of the ball is the concentrated expression of the comprehensive activities gradually formed by the personal analysis system in volleyball, and it is a compound special perception.

From the physiological basis of flexibility, the extensibility of ligaments, tendons and skin across joints is the main reason to improve flexibility. Every joint of the muscle group has good flexibility, and you can accurately feel the weight, elasticity and volume of the ball, as well as its strength, speed and direction. So at present, the best way to improve flexibility is to combine the ball and change the training according to the physiological and psychological characteristics of athletes and the alternating intensity of human activities. An athlete with a good sense of the ball can control the ball at will, reasonably use the functions of various joints of his body according to the changes in the field, that is, he can accurately adjust the strength of the ball, and as a result, he can play a good technical effect. All this requires athletes to be highly flexible.

The book Sports Biomechanics points out that in sports, the level of sports performance mainly depends on the strength of success. (Maximum strength is the maximum explosive force of human body), that is, muscle contraction is not required to be more intense and powerful, but the rebound force of muscle contraction should be increased to improve the jumping height.

In physics, the work (a) done in unit time (t) is called power (w), that is:

W=A / t ( 1)

We know that the work done by muscle contraction is: a = f s (2). Substituting (2) into (1), we can get:

W=F (S / t)=F V (3)

The effect of volleyball run-up and stride jump also depends on human strength, which is equal to the product of strength and muscle contraction speed, that is, w = f v. In order to transform the horizontal speed of run-up into vertical speed, this paper starts from the angle of waist, knee and ankle, obtains some technical data, and analyzes the role of run-up in volleyball.

Pay attention to (1). At the moment of landing, the upper body leans forward and the waist angle is 30 degrees. The fifth step is to step on the ground, return to 20 degrees at the moment of landing, and then lean forward again, with a waist angle of about 30 degrees, until the moment of stepping off the ground, the back bends into a bow state of about 10 degrees.

Knee joint angle: at the moment of stepping, the first step is about 145 degrees, and the second step is about 135 degrees. When stepping on the ground, the knee joint angle in the second step is larger, but with the deepening of the angle, the knee joint angle in the first step is 175 degrees, but the knee joint angle in the second step increases. However, when leaving the ground, the angle of both knees extends to about 170 degrees. ? Ankle, at the moment of stepping, the ankle angle in the second step is 75 degrees, and the ankle angle in the first step is 90 degrees, which is opposite to the knee angle. The ankle joint angle of the first step is greater than that of the second step. When the ankle flexes greatly, the ankle joint is 60 degrees in the first step and 75 degrees in the second step. When kicking off the ground, the ankles of both legs stretch like plates at the moment of kicking off the ground.

The above is the change and extension of waist, knee and ankle in the single action of run-up and jump, which can be explained by formula (3):

W=F (S / t)=F V (3)

When the angle of each joint increases, the length S of muscle contraction also increases accordingly. According to Formula (3), the power W is directly proportional to the length S of muscle contraction, that is, when the value of S is larger, the value of W increases accordingly, which can increase the bounce.

From the influence of the above joint angle changes on the sports level, it can be shown that the spike ability of volleyball players depends on the explosive power of their waist, knees, ankles and lower limbs. Strengthening the flexibility training of each joint plays a fundamental role in improving athletes' jumping ability, and athletes' good jumping ability and full-body explosive force play a key role in improving attack. Different degrees of exercise have different degrees of flexibility. The higher the training level, the better the flexibility. Training plays a decisive role in an athlete's performance, so does the improvement of flexibility. The higher the level of exercise, the more difficult their movements are, which requires higher flexibility.

3.4 Finger and wrist flexibility on the passing effect

The effect of the setter directly affects the outcome of the game. Accurate and elastic passing requires athletes to have good flexibility of fingers and wrists, and the flexibility of fingers and wrists is a direct factor affecting the passing effect.

Guilin Middle School is a traditional volleyball school in the autonomous region. The author once did such an experiment in the "eight consecutive championships" team of middle school students in the city: She Kuai of Guilin Middle School Men's Volleyball Team (admitted to Beijing Sport University). The experiment is like this: standing between 2 and 3 positions, with fingers and wrists immobile and fully active, passing 10 balls from position 4 and returning 65,438 balls from position 2, and getting a set of data:

Good shot at position 4, general error, good shot at position 2, general error.

Movable opening 8 2 0 Movable opening 6 4 0

No activity 4 6 0 No activity 2 6 2

From this set of data, it can be concluded that the success rate of pulling the ball at position 4 is 80% when it is active and only 40% when it is inactive. The passing effect at position 2 is even worse, and the success rate is only 20% when inactive. It can be seen that the second pass with good flexibility of fingers and wrists is better than the second pass with poor flexibility, because the movement range of fingers and wrists is small and the elasticity is poor when passing the ball, which reduces the buffer of the ball in the hand, thus reducing the adaptability to the ball. This happens in the back pass, because the fingers and wrists are not stretched well and the ball can't be passed out. Therefore, in order to improve the quality and effect of the setter's passing, we should strengthen the quality training of the setter's finger and wrist flexibility.

3.5 Flexibility helps to prevent injury.

Poor flexibility often leads to sports injuries. In volleyball, the shoulder joint is the most widely used, such as spiking and serving, with a wide range of activities. If the flexibility is poor, the ligament of the shoulder joint will be damaged. According to the investigation, among the 6 main players of Guilin Middle School Men's Volleyball Team, 2 players were injured in the shoulder ligament, accounting for 33.3%. Therefore, the range of motion of shoulder joint is reduced, which affects sports technology.

4. To sum up, the following conclusions are drawn:

4. 1 Flexibility is an indispensable physical quality for volleyball players.

4.2 Flexibility is directly proportional to the level of motor skills.