Lumps in the breasts after exercise can be caused by trauma from exercise and may be associated with conditions such as breast enlargement, mastitis, and breast tumors. When trauma to the breast occurs as a result of not paying attention to the method of exercise, it may lead to a lump in the breast. However, it may also be the case of the following diseases. 1. Breast hyperplasia: Patients with breast hyperplasia will have lumps in their breasts, and usually have nipple discharge and breast pain. Symptoms are obvious before menstruation and after anger. 2. Mastitis: If the patient is breastfeeding, due to the milk stagnation, it may block the mammary glands, and the patient will have symptoms such as lumps in the breast, redness and swelling of the breasts, pain, and localized fever. 3. Breast tumor: it can be divided into benign and malignant tumors. Benign tumors are mainly manifested as breast fibroids, etc. Typical symptoms are lumps in the breast, which can be accompanied by slight pain. Malignant tumors are mainly manifested as breast cancer, in addition to lumps in the breast, there may also be nipple blood spilling, breast cellulite-like changes and other symptoms. In addition, breast cysts, breast trauma may also cause similar symptoms, women should consult the doctor in time, do a systematic examination to clarify the cause of the disease.