In fact, both chest training and training will lead to the growth of chest and waist muscles. As mentioned in the soft answer below, the fibers of the pectoral muscle are horizontal, while the rectus abdominis is vertical. If muscle fibers also increase, the bust will increase more than the waist. On the other hand, chest circumference and waist circumference are not only determined by muscle thickness, but also influenced by the shape of chest and abdominal cavity. There is no rib support in the abdominal cavity, and exercise will tighten the abdominal muscles, thus contracting the abdominal cavity and making the waist look thinner. At the same time, it will tighten the intercostal muscles, expand the ribs and enlarge the chest.

It seems difficult to understand this small one and a big one. Let's do it step by step.

The action that directly affects the size of the chest and abdominal cavity is "breathing". There are two kinds of breathing: chest and abdomen. The former is intercostal muscle contraction to lift ribs and diaphragm, while the latter is abdominal muscle contraction to press abdominal cavity to lift diaphragm.

Specifically, you can see the column of senior engineer coach: Breathing-Health Management-Zhihu column.

People who lack exercise tend to breathe shallowly, and their abdominal muscles and intercostal muscles are weak. Try to sit quietly in the chair, close your eyes and take a deep breath, then spit it out slowly, relax all over, and then feel the body feeling with the shallowest breath. Do you feel as if something is falling in your heart?

This is the feeling that the diaphragm falls under the action of gravity in a relaxed state. People who lack exercise for a long time have low oxygen consumption and shallow breathing. The descending diaphragm constricts the chest, and at the same time the abdominal cavity is squeezed, like a deflated balloon, and its circumference becomes larger. It forms a barrel-shaped or even olive-shaped figure.

Let's look at another thing:

& gt As we all know, if the rubber band is stretched for a long time, it will gradually lose its elasticity, resulting in the central ring becoming larger than before. The principle that the human body has muscles is very similar to that of rubber bands: as we all know, if rubber bands are stretched for a long time, they will gradually lose their elasticity, resulting in the central ring becoming larger than before. The principle that the human body has muscles is very similar to that of rubber bands:

The position of transverse abdominal muscle is hidden in the rectus abdominis (eight-pack abdominal muscle) and oblique abdominal muscle (mermaid line), and the muscle fibers are transverse. Because the abdominal cavity is squeezed, the body needs a "band" to wrap the stomach against this force, and the transverse abdominis muscle is this band. Due to long-term tension, the transverse abdominis muscle is elongated, and due to lack of exercise, the rubber band gradually loses its elasticity (transverse abdominis muscle strength). The waist is getting thicker. The position of transverse abdominis is hidden in rectus abdominis (eight-pack abdominis) and oblique abdominis (mermaid line), and the muscle fibers are transverse. Because the abdominal cavity is squeezed, the body needs a "band" to wrap the stomach against this force, and the transverse abdominis muscle is this band. Due to long-term tension, the transverse abdominis muscle is elongated, and due to lack of exercise, the rubber band gradually loses its elasticity (transverse abdominis muscle strength). The waist is getting thicker.

In the process of fitness, squat, bench press, belly roll and even running all need the core (waist and abdomen), and the strength of transverse abdominal muscles will be improved. On the other hand, the body's oxygen consumption will increase, the breathing frequency and depth will be strengthened, and the strength of diaphragm and intercostal muscle will also be improved. After the strength of these muscles is improved, the chest will rise and expand, and the abdominal cavity will tighten, so that the chest is big and the waist is thin. The biggest change is in the first few months of exercise. In the first two or three months of fitness, the waist circumference shrank from 82 to 76, and the chest circumference rose from 90 to 92, and then the change was very slow.

When training to a certain extent, waist circumference and chest circumference are determined not only by chest and abdomen, but also by muscle circumference. Bodybuilding practitioners will pay great attention to the ratio of chest to waist, especially the participation of core strength (such as the transfer of power source to buttocks) and the position of pelvis (pelvic tilt and backward tilt refer to abdominal muscle strength). The ratio of chest to waist is also one of the criteria for bodybuilding evaluation. In addition, the broad mind actually accounts for a large part of latissimus dorsi visually, and the abdomen will also be beautiful. Mr. phil sith, do you think the breasts are too big? Ultra thin waist! But from another perspective, ...

Non-bodybuilding training generally attaches importance to core strength, such as ball players, heavyweight boxers, weightlifters and Hercules. A strong core strength is inseparable from a strong waist and abdomen. Take a look at @ Binka's: How does waist and abdomen strength help header?

C Ronaldo has a thick waist.

Visually, it is the external oblique muscles on both sides that cause the waist to be thick. Weight-bearing training of external oblique muscles will straighten the waist line, such as the flexion and extension of Roman chairs, the flexion and extension of dumbbells, wipers, barbell torsion and so on. As long as the average girl reduces her body fat to below 22% and activates the strength of transverse abdominis, she will naturally look slim. Don't worry ... you can't build Liu Chunhong's waist and abdomen.

Recommend several exercises:

The plank support (plank) should not collapse. In the state of collapse, the stress on the back will be greater, so don't bow your back. Bowing the back will squeeze the abdominal cavity, which will not achieve the effect of slimming the waist. The position of pelvis is as neutral as standing posture. Don't collapse. In the state of collapse, the stress on the back will be greater, so don't arch your back, which will squeeze the abdominal cavity and fail to achieve the effect of thin waist. The position of pelvis is as neutral as standing posture.

Abdominal roll (full range)

& ltimg src = "/9cee0e81f 71f8b0fa77b046142d7524f _ b.jpg" data-rawwidth = "404" data-rawheight = "237" class = "content. It is suggested to put a towel, as shown in the figure. When you get up, you should bend from the thoracic spine until it is completely tightened. Never start from the lower abdomen. Feel the layers of abdominal muscles squeezing. At the beginning, you can use more strength to assist your hands. After the abdominal muscle strength is activated, your hand will slowly relax, and finally the towel will be taken off. It is suggested to put a towel, as shown in the figure. When you get up, you should bend from the thoracic spine until it is completely tightened. Never start from the lower abdomen. Feel the layers of abdominal muscles squeezing. At the beginning, you can use more strength to assist your hands. After the abdominal muscle strength is activated, your hand will slowly relax, and finally the towel will be taken off.