Javelin is a complex multi-axis rotating event, which requires athletes to be fast, responsive and have strong coordination and exertion ability. Due to the characteristics of javelin movement, javelin athletes should not only have good explosive power, running and jumping ability and coordination, but also master reasonable final exertion techniques. Therefore, in the five links of javelin throwing technique, the grip, gun run-up, throwing step, final exertion and buffering, the final exertion stage is the most important.

2 Analyze the technical action of javelin throwing in the final exertion stage

Finally, the force is to make full use of the impulse obtained from the run-up speed, and exert the maximum force on the javelin in the farthest distance as possible, so that the gun can be thrown with the maximum force and reasonable angle at the moment of shooting. Its main task is to make good use of the cross step to make the lower limbs surpass the upper body and do a good job of surpassing equipment. Of course, beyond the equipment is not infinite, but suitable for maximizing muscle contraction force and minimizing the loss of horizontal speed during exercise.

The data show that the final exertion stage begins when the kick and the body posture considered as the final exertion generate horizontal thrust, that is, when the right foot touches the ground and the center of gravity of the human body is far away from the fulcrum of the right foot. Javelin athletes should focus on improving or maintaining the run-up speed when forming the final hard posture, which requires reducing the horizontal braking as much as possible during the right leg landing and pedaling, so as to minimize the speed loss. In order to reduce this braking, it is necessary to prepare for the subsequent cushioning action when the right foot touches the ground. Because after the body leans back to the ground, the buffer range of the ankle joint is small, mainly by bending the knee. Therefore, when the right foot touches the ground, the knee joint of the right leg should have a certain angle (about 170 for men and 165 for women). At this time, the slight flexion of the right knee is beneficial, and it is also quite necessary to cushion the subsequent knee flexion. At this time, the toe direction of the right foot should form an angle of about 45 with the throwing direction. When the right leg is straight, the toe direction of the right foot is the same as the throwing direction. This shows that the tip of the right foot rotates in the throwing direction in the process of stretching the right leg. Therefore, in order to facilitate the rotation of the right toe, the angle between the right toe and the throwing direction should be minimized when the right foot touches the ground.

After the right leg is cushioned, the braking is reduced. As the body's center of gravity moves forward, the right knee still keeps a certain angle, and the right leg begins to exert force. The right leg mainly extends from the hip and ankle, commonly known as "kneeling and pedaling". The right leg is fast and powerful, mainly forward. The purpose of exerting force is to accelerate the translation of hips and lower limbs and make the left foot land quickly. When the left foot falls to the ground, it forms a strong and stable elastic support for the left side, which makes the left side suddenly brake, thus causing an acceleration to the right hip. The deceleration of the left buttock and the acceleration of the right buttock lead to the rotation around the left buttock. Rotation is not only manifested in the vertical axis, but also through the horizontal axis movement of the front foot and buttocks, thus making the athletes rotate in the throwing direction and providing the necessary momentum for the final throwing.

The research shows that when the elite javelin throwers use their left leg to move forward in the last hard step, their left leg should be as straight as possible, lower from the ground and move forward quickly, so that the left leg can land quickly, so as to speed up the forward movement of hips, upper body and javelin. The more effective the left leg braking is, the greater the strength loss of the lower limbs and the greater the momentum gained by the upper body and javelin. Therefore, the left leg support is an important link to transform linear speed into rotational speed and realize momentum transfer. The quality of left leg support braking directly affects the speed of transferring momentum from lower limbs to trunk, which is an important condition to accelerate the forward and upward movement of upper limbs and instruments, and also an important link to form "full bow". If the left leg is not well supported and braked, the left foot touches the ground, and the left knee joint is excessively bent, which can't bear the # # force exerted on the left foot by the quick run-up, which will inevitably lead to the failure of support, the muscle strength of the trunk and upper limbs can't be better exerted, and the javelin throwing speed will be affected. Therefore, in order to achieve effective momentum transfer, the left foot must brake hard. The better the braking effect, the greater the momentum loss of lower limbs, and the greater the momentum gained by human body and javelin. Therefore, the quality of left foot braking technology is the prerequisite for the momentum of lower limbs and human body to be quickly transferred to javelin.

The research shows that the change of the angle of the left knee joint can directly reflect the braking effect of the left leg, and it is an important index to measure the momentum transferred from the support reaction to the javelin through the knee joint. The technique of left knee flexion, buffering, pushing and stretching is an important action of momentum transfer, which also plays an important role in making full use of lower limb strength and improving javelin throwing speed, and is also the key to the final force effect. In the final exertion stage, the body posture after the left leg touches the ground and bends its knees is the lowest stage of the whole throwing process. At this time, due to the braking on the left side, the hip rotates forward quickly around the longitudinal axis of the left leg, and at the same time drives the upper body to approach the left fulcrum. Then the left side explosively kicks and lifts hips, waist, chest and javelin, and the body center of gravity reaches the highest at the moment when javelin is released. The trajectory of the human body's center of gravity from low to high has the advantages of increasing the throwing radius and lengthening the throwing arm, as well as obtaining the vertical speed. This shows that the trajectory of the center of gravity of the human body suddenly rises from low to high, which plays an important role in the performance.

The technical movements of lower limbs in the final exertion stage of javelin throwing are very complicated, and the athletes' ability to coordinate exertion is quite strong. This set of movements requires athletes to complete quickly in a fairly short time. Therefore, in the final exertion stage, it is necessary to speed up the exertion, shorten the exertion time, and let the equipment fly further.

3 Conclusion

In the final stage of javelin throwing, when the right foot hits the ground, the right knee should have a certain angle, and the tip of the right foot should point to the throwing direction as far as possible. The right leg is mainly used to stretch the right hip and ankle; The braking of the left leg support should be rapid and sufficient, which is an important link to convert linear speed into rotational speed and realize momentum transfer. In the final exertion stage, it is necessary to speed up the exertion and shorten the exertion time. ■