Breast trembling can be caused by oversized, sagging, and breastfeeding. Many women would like to have larger breasts, but factors such as genetics, race, overgrowth of breast tissue, and body obesity can lead to larger breasts. When breasts are too big it can affect daily life, running, strenuous exercise can cause breast trembling. With age, excessive weight loss will lead to breasts lack of fat support, which will lead to breast sagging phenomenon, walking or exercise amplitude is too large, flaccid sagging breasts will appear shaking, trembling, so in the daily exercise should wear appropriate underwear to avoid excessive friction in the chest to form skin lesions. During the breastfeeding period, there is enough milk in the breasts, and the breasts will be much larger than before. At this time, the breasts are harder and fuller, and since the breasts are loose tissue organs hanging in front of the chest, as long as there is a little activity, it will vibrate to the breasts, resulting in the breasts trembling.