In swimming learning, I feel that there are often students who swim standing up. Hip sinking, body leaning and even "standing and swimming" often occur. Analysis of the reasons, in addition to technical aspects, is mainly the relationship between the center of gravity and the floating center. When a person lies on the water, due to the downward gravity generated by the weight of the person, the resultant point is called the center of gravity. According to Archimedes' principle, people will naturally produce an upward buoyancy in water, and its resultant point is also called floating center. Because the internal organs in the upper chest are light and the proportion of lower limbs is greater than that of the upper body, the floating center is close to the upper body and the center of gravity is close to the lower limbs. People lying flat on the water will lose their balance because the center of gravity and the floating center cannot coincide. Therefore, in the process of swimming, in order to keep the body in a horizontal posture, the center of gravity must move forward.

According to the above principles, combined with my own experience, the ways to overcome "standing swimming" are as follows: First, don't hold your head too high. If the head is raised too high, it will inevitably cause the chest to rise. This will not only make the center of gravity move forward, but will make the center of gravity stay down, causing the buttocks to sink. When you look up and inhale, you can keep your mouth out of the water. After inhaling, you should immediately lower your head and dive, so that the center of gravity can move forward quickly and increase buoyancy.

Second, when you stretch your arm forward, you should take the initiative to stretch forward, and don't stroke your arm too early. Beginners of breaststroke are often eager to paddle before their legs are completely straight, their elbows are not straight and their shoulders are not pulled forward. As a result, the stroke route is short, the strength of chest, back, shoulders and other muscle groups can not be fully exerted, the buttocks sink and the resistance increases. Therefore, the arm is required to stop quickly at the end of the stroke, and reach the front middle arm and consciously stretch forward until the elbow joint is straight and slides forward. When the body is straight, don't row your arms immediately, but also make full use of the traction of kicking, experience the center of gravity moving forward and keep your body straight.

Third, the stroke arm should not be too wide or after. Beginners in breaststroke often stroke their arms too wide or too late, which easily leads to late inhalation, small support area, too high head, lower center of gravity, backward extension of arms, chest holding and lower center of gravity. When kicking, the arm can't stretch forward in time, which will affect the cooperation between the leg and the arm, make it difficult for the center of gravity to move forward, lower limbs sink, and the body can't be completely straight. Therefore, beginners are required to do small paddling, that is, the arms are slightly flexed, and the paddling is slightly wider than the shoulders below the side slope. Don't cross the shoulders, and ask to see your elbow joint close to your head, so that your body can be balanced.

The second article

Breaststroke leg movement is one of the main driving forces to promote the body forward in breaststroke swimming, and its action effect plays an important role in swimming performance. The leg movement of breaststroke is more important than other strokes, which not only maintains the balance of the body, but also produces greater propulsion. The leg movements of breaststroke are divided into four parts: leg adduction, eversion, kicking and sliding. But they were closely connected and complete movements at that time. Leg adduction and eversion are the stages of generating resistance, while pedaling and sliding are the stages of generating driving force. The former should not only produce as little resistance as possible, but also create conditions for the latter to produce as much driving force impulse as possible. Therefore, it is of great theoretical significance and practical value to analyze the leg movements of breaststroke and put forward reasonable leg techniques to provide theoretical basis for improving the speed of breaststroke.

1. Breakdown of leg technique in breaststroke

1. 1. Close your legs.

Leg adduction not only does not produce propulsion, but also brings resistance to the body, so we should consider how to reduce the resistance.

Due to paddling and breathing, the hip joint, thigh and knee joint all sink slightly when the leg is retracted. When you retract your legs, your knees bend and your hips bend at the same time. When retracting forward, the knees gradually separate and the ankles extend. The calf and heel are behind the thigh and hip, and the projection section of the hip joint is easy to contract forward, reducing resistance. Stop retracting your legs when your feet are close to your hips. From the point of view of reducing resistance, leg retraction should be completed at a slow speed. But at a higher level, in order to save time, speed up the action frequency, and cooperate with the paddling action, the leg retraction should be completed quickly. In addition, after the thigh and knee joint sink, the calf and foot are located behind the thigh, and the rapid retraction of the calf at this time will not form too much resistance. But beginners must first master the rhythm of slowly closing their legs.

1. 1. 1 the difference between flat breaststroke and wave breaststroke.

There is a significant difference in leg adduction between flat breaststroke and wave breaststroke. In flat breaststroke, the thighs are greatly contracted. At the end of calf adduction, the thigh and trunk form an angle of about 120 degrees to 140 degrees, and the knee is about the same width as the hip joint. The angle between thigh and calf is about 40 ~45 degrees, which is because the body posture of breaststroke is relatively flat. If the thighs are too small, the calves and feet will be exposed to water during the leg retraction, which will destroy the balance of the body. On the other hand, the thigh is greatly retracted, which increases the water-retaining section of the thigh, increases the shape resistance and reduces the forward speed.