Generally speaking, people with high body fat rate will have larger breasts (regardless of gender); Because the higher the body fat rate, the more chest fat, the more chest fat, the bigger the chest. Women just warm up and sprint, which has no obvious effect on getting bigger or smaller breasts, but women can slim their breasts by jogging for a long time.
When running, because of the swing of the upper limbs, the chest is not shaking up and down, but shaking in a figure of eight. The smaller the protective measures, the greater the shaking. This is about girls. If you are a man, you don't have to think so much. Even if your chest muscles are big, I believe that you will not sag if you continue to exercise.
When a girl runs, her chest swings in a figure of eight. If it takes too long, it will damage the connective tissue around her breasts, tear the pectoral muscles, and lead to long-term sagging of her chest. Of course, this is for girls with big breasts. If you are an airport, don't worry.
The more intense the running, the bigger the chest, and the higher the probability of injury. The specific shaking times are related to the operating frequency. Research shows that when you run 1609 meters in ordinary underwear, your breasts will shake 135 meters. Even with a 34A cup, your breasts will leave your body 4.2 cm during exercise. A 36-year-old female, her chest jumped up and down about 1 1.9 cm during exercise.
This large-scale shaking will permanently damage the elastic fiber tissue in the breast, leading to relaxation, sagging and deformation of the chest.