Yes, if you don't wear a sports bra when running or jumping. Your chest will swing involuntarily and cause permanent damage to the elastic fiber tissue in the breast. According to statistics, 50% of the women interviewed don't know that the violent shaking of the chest during exercise will hurt the elastic fiber tissue of the breast and lead to sagging of the chest. Excessive exercise or careless underwear during exercise may hurt breasts. People with big breasts will droop, while those with small breasts will get smaller and smaller. Pay special attention to chest reduction exercises such as running and skipping. You must wear a sports bra to protect your chest when exercising.