1. Research purpose

? The college entrance examination for physical education majors in Guangdong has just ended. In this exam, the results of shot put in situ are generally not high. The author summarizes and analyzes the reasons on the basis of observing the skills of candidates. ? Since 20 19 is the first year of changing solid ball into shot put, it can be seen from the bulletin board of sports results that the average score of men's shot put is about 9.5-10.5m, and that of women is about 7.3-8.3m.. Women's shot put is an event that loses a lot of points after changing to solid shot put. Because of their relatively weak strength, it is more difficult for girls to get high marks in shot put.

? There are few perfect scores in this exam, which is in sharp contrast to the previous situation that each group has 2-3 perfect scores. This also shows that due to the change of the project, candidates lack enough time to complete the strength training replacement cycle required by the shot put project, and most candidates are still applying the strength training plan for training solid balls, which has caused the bottleneck of improving throwing performance.

? Through the on-the-spot observation of candidates' warm-up before the exam, most candidates adopt forward push-ups to put the shot (hereinafter referred to as forward push-ups). Although this throwing method is simple and easy to learn, the technical theory is easy to understand, and it mainly emphasizes fast and coherent, but the effect of improving the throwing performance of most athletes is very limited. A small number of candidates choose other methods, the most distinctive of which is the back throw method, which has made a great breakthrough.

? These two methods have their own characteristics, so I discuss the differences between the two technical actions from the aspects of mechanical analysis and practical training operation, and analyze the reasons for the differences, hoping to find a solution to the problem.

2. Research methods

? The core significance of technology is to realize the transfer of body kinetic energy to throwing equipment, and the key moment of all throwing events is the moment when the equipment leaves the palm or finger and is thrown. Throwers need to pay attention to how to control the body and equipment, so that the kinetic energy generated by the body can be transferred to the center of the equipment to the maximum extent, and the equipment can be thrown into the air at a correct angle and in a reasonable posture. High-level throwers understand that body and equipment should be integrated.

? The basic technique of shot put also reflects this process: from the preparation of throwing, the first action comes from the right foot. Push your heels hard, turn your knees in the throwing direction, and unfold your twisted body. This powerful unfolding, lifting and pushing of the body shifts the center line of the body from hips, chest and shoulders to arms, wrists and hands. The shot put at this time comes from the superposition of rotation, straight line and vertical force.

? The main technical difference between forward and backward throwing is whether the trunk (hip) is in a state of deceleration or acceleration when the human body exerts force on the shot put. The former is in the stage of centripetal contraction, like deceleration after sprint, while the latter is in the stage of centrifugal contraction, like acceleration of starting.

? Secondly, the angle between the arm and the body, the position of the feet and the control of the body have different requirements. The overall effect caused by the two is completely different, and the probability of technical problems is also different, which puts forward different requirements for athletes' core strength.

? The author divides PE students into two groups, and tests each student's initial score and average score. After the training began, one group learned the forward throwing method and the other group learned the backward throwing method, and recorded the test results every 2-3 months. At the same time, according to different training methods and plans and strength training items, the differences between the two techniques are analyzed.

3. Research results

? After nearly 1 year statistics, according to the performance data of each athlete in each stage, the corresponding scores are obtained according to the latest college entrance examination scoring standards, thus objectively reflecting the progress range and overall level development of each athlete in each stage.

Table 1 analysis table of shot put scores (corresponding to college entrance examination scores) of two groups of athletes at different stages

? Table 1 Using the latest Guangdong college entrance examination scoring table standard, we can objectively measure the achievements of men and women on a unified standard. Although women's general strength foundation is weak, they can get better room for progress.

? As can be seen from the data, the second group of athletes adopted the back throw method for training when their basic performance was generally weaker than that of 1 group, and made great progress in their performance. In the end, the players who can surpass 1 group in an all-round way get the advantage of an average score of nearly 7 points.

? The contrast between the two techniques is only that the progress value is different when the initial strength level of athletes is similar. That is, athletes with the same level of strength will make greater progress by adopting more advanced methods. Some athletes with relatively small strength are at the upper-middle level in the performance of solid ball, reflecting that their proficiency in mastering technology is relatively mature and their core strength is relatively strong.

? In addition, because the shot put performance mainly depends on the athlete's own physical fitness and coordination, good training methods can effectively improve the athlete's performance, but a good strength foundation is also very important.

4 Analysis of research results

4. 1 From a technical point of view

? The technique of forward throwing is relatively simple: the center of gravity is required to move horizontally and quickly when throwing. With the movement of the center of gravity, the center of gravity of the body exceeds the front foot and the upper body leans forward. When pushing the ball, the throwing hand's arm is upward, providing an upward hand angle, and the method of adjusting the curvature of the ball, so that the front and rear feet take turns to exert force and produce forward speed. Because there will be obvious forward movement, this throwing method is simple and effective, and it can speed up the player's speed, sometimes leading to the rotation of some shoulders to increase the range of movement.

? The whole movement is simple and easy to learn, but it ignores the foundation of the body's kinetic energy, that is, the strength generated by muscle groups. Although the overall movement will look coherent and effective, it still can't get rid of the shoulder joint as the main muscle group. However, the shoulder joint muscle group is not the most explosive muscle group in the upper limb strength muscle group, and the pectoralis major hardly participates in the whole strength process, which also limits the transfer of body kinetic energy to throwing instruments from the source of strength.

? Fig. 1 the third stage, as shown in fig. c, when the force is applied instantaneously, the upper arm is basically parallel to the body and belongs to the lifting stage. It can be said that most of the thrust comes from shoulder muscles, mainly the front and middle bundles of deltoid muscle, followed by triceps brachii, latissimus dorsi and serratus muscle.

? The technique of back throwing is more complicated: the braking left leg on the toe board should try not to exert force in the process of forward and upward force transmission. Brake one leg to restrain the rotation of the body, so that all the forces act on the instrument and the shot put is pushed out. The right leg drives the hips to turn, turns to the left leg, drives the shoulders and the shot put. Because the body is twisted before the shot put, the rotation of the right knee drives the left arm to leave. When the left arm is thrown to a position parallel to the chest, it rotates with the chest, just like pushing a door with the left arm.

? When the body turns to the throwing direction, the left arm stops or prevents the shoulder from turning further. Lock the left upper body tightly in a fixed position when putting the shot. During the throwing process, the head is thrown back to a fixed position, and all the strength is exerted on the shot put. When putting the shot, the legs are used to lift and turn the body.

When throwing, the center of gravity should be controlled to move from low to high. When throwing, the body should be upright, the hips should be slightly raised, and the thrower's arms should be vertical to the upper body to ensure that the arms are pushed horizontally. Relying on the support of the front and rear feet, the upper body leans back slightly, so that the chest is inclined upward, and the curvature of the parabola of the shot put is adjusted by the range of leaning back. When throwing, the center of gravity is required to be controlled between the legs, and the body is not allowed to lean forward and rotate excessively.

In the third stage diagram C of Figure 2, the upper arm is basically perpendicular to the trunk when the force is applied instantaneously, and most of the thrust comes from pectoralis major, followed by triceps brachii, latissimus dorsi and serratus anterior. ? The adjustment of the flying radian of the back throw method mainly depends on the backward inclination of the body, and the arm should be pushed vertically to the chest to produce the maximum thrust. Therefore, the waist is required to have a certain supporting force, and at the same time, the rotation of the hip is used instead of the rotation of the lumbar spine, and the adduction force of the pectoralis major is combined to throw the ball. Brake and slow down at the moment of throwing to avoid excessive rotation of the body.

? When the force instantly acts on the shot put, the state of the hip joint is very different from the angle of the body support. From the overall physical state analysis, the former leans forward and the latter leans back, which also determines the main muscle group, the shoulder muscle group of the former and the chest muscle group of the latter. Because the maximum strength of pectoralis major is almost 4-5 times that of shoulder muscles, the back throwing method can tap the maximum energy of the body and has great development potential.

4.2 The training methods of the two throwing methods are different.

? Because the two throwing methods are basically the same in preparation and initial movements, both of them have fast hip rotation, twist and other body movements, but because of the different training emphasis, the forward throwing method emphasizes the height of the throwing point and has no requirements for hip movements. The back throw requires high hip skills, so the two throwing training methods are also very different.

? Training means of forward throwing: provide a relatively high target, such as a high leaf or a benchmark, train with or without the ball, and develop the dynamic stereotype of the master. For example, throw a solid ball at the wall and set the target height of the landing point.

The training method of backward throwing: practice the pushing technique of pectoralis major muscle in the throwing direction from the parallel foot in situ. Fix the rubber band with your right elbow and practice swinging your elbow inward, mainly to exercise the transceiving force in pectoralis major. Lift the tendons with your left hand, and practice the supporting actions of pushing the ground and turning your hips, chest and back. At the initial stage of training, athletes are required to hold a fixed upright pole on the left side (throwing with the right hand). The main purpose is to reduce the training that restricts the athletes' body rotation and leaning forward, limit the forward movement of the center of gravity and reduce the range of body rotation, and develop the dynamic stereotypes of controlling the center of gravity and hip chest push. (Figure 3)

4.3 Different positions of feet in preparation.

? The forward throwing method requires that the distance between the athlete's feet is 1- 1.5 times the shoulder width, and the position selection will generally be reserved at a distance of 0.5- 1 m from the baffle to prevent excessive forward stepping out of bounds. Too short a distance between feet will also lead to the center of gravity quickly surpassing the body and losing control in the throwing process. Therefore, when using this throwing method, some athletes will rush 1- 1.5 meters before the meeting. As shown in part a in fig. 4.

The back throw requires that the distance between the athlete's feet should be more than twice the shoulder width, and the position selection is generally to reserve 0. 1-0.2 meters from the baffle, or even to press one side of the front foot against the baffle. The extra-long distance between the two feet not only increases the acceleration distance of the athlete when throwing, but also keeps the body center of gravity above the straight line between the two feet before and after exerting force. In particular, the support of the front foot can generate vertical upward thrust, make the body jump upward, increase the height of the hand, and ensure that the center of gravity of the body is stable in the throwing circle. As shown in part b of fig. 4.

4.4 Probability of "shooter" in the strength stage of two throwing methods

Although athletes will put the ball at the root of their fingers in advance, the process of holding the ball is not affected by the size of their fingers. The final stage of normal throwing technique is to rely on the strength of fingers and wrists, with the thumb facing sideways and picking up the ball horizontally. Because the speed is extremely high, not only the arm is pushed out, but the consistency of the fingers and wrists. The aim is to apply all the speed to the ball.

? The technical characteristics of forward-leaning throwing method will lead to the shot put directly under the palm of your hand in the shooting stage, which will lead to the moment when the ball is pushed out and become a one-handed shooting action similar to basketball. The main reason is that the athlete wants to lift the height of the master when he shoots, but the height of the forearm remains unchanged because he leans forward and presses down. Causing the movement to deform. Once the "shooter" appears, it will lead to problems such as high parabola, throwing the ball, loss of strength, etc., which will not only affect the performance, but also seriously lead to the athlete's finger contusion and dislocation.

In the training method of back throwing, it is one of the key requirements to avoid leaning forward and pressing down. Starting from the practice of throwing your feet in parallel and forward, you can send an oblique solid ball (big solid ball) from your chest with your hands backward, and develop the habit of exerting force on the pectoralis major muscle. Through long-term persistence, the number of "shooters" in the throwing process of athletes who learn this method is obviously less than that of the forward throwing method.

4.5 Differences in Strength Training

4.5. 1 training differences of core strength

? The forward throwing method is to accelerate the left and right of the waist core strength in training, that is, to make the body centrifugal contraction stage, just like accelerating the start. The strength of the lower limbs is transmitted to the upper limbs, so the main training is to do light weight traction training. This kind of rapid explosive training, which is close to actual combat, often causes waist pain because it contains a lot of waist rotation movements.

? The back throw is in the centripetal contraction stage, just like the deceleration after the 100-meter sprint. Its main part is not the lumbar vertebrae but the rotation of the hip joint, so this method takes the core strength as the functional training to maintain the body angle and restrain the rotation, especially the training of body rotation focuses on resistance training and "peak contraction" training. The long-term training results show that this training method can effectively reduce the problem of athletes' waist injury, and at the same time, it can well complete technical movements and improve athletes' performance.

The absolute strength of athletes has a great relationship with the shot put performance, which reflects the strength of athletes' comprehensive strength quality. At present, it is generally recognized that the three strength qualities of athletes (bench press, squat and maximum weight of hard pull) are directly related to the shot put performance. As can be seen from the following table, basically most athletes' shot put performance is corresponding to their three strength values.

Table 2 Maximum Strength Test Value and Shot Put Performance Analysis Table

? Height and coordination also play a vital role. For example, although the third strength level of player No.2 is very high, due to coordination problems, his movements are incoherent, and his score does not exceed 1 1 meter. Players 1 1, although the three strength levels are very low, they can achieve good results because of their high height and good cooperation. These two types of athletes are extreme phenomena, but they also illustrate the importance of coordination and the direction of talent selection for shot putters.

? Front throw and rear throw depend on waist strength differently, so there are great differences in project selection. Forward throwing is mainly based on pushing up. As usual, the barbell is selected for continuous sprint and push-up as explosive force training, and the deltoid muscle in the shoulder muscles is mainly trained by the front (back) push of sitting neck. Bench press, upward oblique bench press and triceps brachii training are supplemented. The quantity is between 8- 12. Like what? Jumping to push the barbell up to the shoulder or pushing the barbell vertically with one arm is mainly to improve the explosive power of athletes and train with the weight of 30%-50% 1RM.

Strength training method of backward throwing: Athletes' explosive power is practiced by Olympic lifts such as high throwing and snatch, while chest and back exercises are strengthened by hard pulling and bench pressing, shoulder pressing and triceps brachii training as supplements. The core strength is mainly the hip flexion and extension muscles, such as lifting the hip with weight. The lower limbs and core strength are practiced by using the continuous left and right snatch barbell frame, and the barbell piece pulls elastic belt's body rotation as a supplement.

4 Result analysis:

The forward throwing method is easy to understand, simple and easy to operate, and is widely used in teaching. However, its shortcomings are also obvious. In actual operation, it is easy to make mistakes and lose the ball, which is easy to cause waist injury. Due to the difficulty of back throw, some athletes who have short practice time have some excessive body movements and the process of exerting force is prolonged. However, excessive rotation of the body causes the decomposition of strength, which affects the synthesis of strength and reduces the effect of strength on shot put. To solve this problem, it is a long process to improve the targeted core strength of athletes to curb excessive rotation in time.

On the premise of the same absolute strength, the backward throwing method can achieve better results than the forward throwing method. This is mainly due to the different proportion of muscle groups involved in the body, which leads to different forces acting on the shot put. Because the two methods have different emphases in the strength training plan, and because the related muscle groups lack exercise for a long time, it is difficult for many students to greatly improve their performance in a short time when they want to change their throwing methods.

? Some people think that sticking to the practice of leaning forward can also give the shot a perfect score. But one or two special cases can't prove that the shoulder-throwing method is the best training method. This has a certain relationship with the development of athletes' own strength muscle groups. If students have developed strong shoulder strength, the developed strength of pectoralis major muscles may not be as good as that of shoulder muscles. Changing the throwing method immediately will not significantly improve the performance. But if there is enough time, the potential for improvement is still considerable, especially when the shoulder muscles and triceps brachii are developed.

Strength quality is closely related to the improvement of shot put ability, so it is necessary to ensure enough strength training time, and carry out strength training 2-3 times a week according to the physical development of athletes. At the beginning, shorter and heavier players performed better in explosive power. The taller the player, the more obvious the later progress, probably because the height is conducive to better radian. This also shows that when the strength rises to a certain extent, the difference between the two technologies can be objectively reflected.

Five suggestions:

Learning to throw backward is a long technical process, which requires athletes to have strong core strength and comprehensive physical strength. It is very unwise for anyone to bypass strength training and make a qualitative leap in his performance just by mastering the prequel quickly. Only by fully exploring the limits of the overall strength of the body and seeking ways to surpass ourselves day after day can we "surpass the equipment" and achieve super-long play.

Increasing the range and speed of exercise will have a great chance of causing lumbar muscle strain, and the recovery speed will be extremely slow, even ruining the athlete's whole sports career. When many coaches like to practice waist and abdomen strength, they require athletes to complete it quickly, and the greater the range of action, the better, but less exercise on hip joint. The function of core strength is mainly to keep the body upright, not to increase the range and speed of movement. Among them, the rotation and movement of hip joint play an extremely important role.

Studies have proved that the role of core strength in sports is to maintain stability or inhibit rotation, or to help lock the body in the air. Therefore, in the practice of designing core strength, it is necessary to increase the practice of keeping fit accordingly, so as to enhance the core strength more effectively, such as 2-3 fulcrums with one hand or one foot support with one hand. Especially the strength of hip rotation is the key to improve the shot put performance.

In addition, the strength training of shot put should pay attention to the training of maximum strength, the importance of training should be close to more than 85% of the maximum weight that can be executed at one time (1RM), and the number of times in each group should be gradually reduced to less than 6 times. And keep enough rest between groups for more than 3 minutes. If 10 is selected as the maximum weight that can be executed, more repetitions in each group will only increase muscle mass, and the maximum strength is not obvious.

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