Swimming during the day and sleeping at night, the heart several times suddenly jumped because of overwork, mental illness, hyperthyroidism, cardiac arrhythmia, anemia and so on. 1. Excessive exertion: swimming is a very high-intensity sports, cardiorespiratory function have certain requirements, if the usual little exercise, sudden large exercise will make the body overworked, appearing short-term neurological dysfunction. After rest will be better. 2 mental factors: if you have recently felt too much mental stress, there will be nervous dysfunction, there will be heart discomfort. 3. Hyperthyroidism: excessive secretion of thyroid hormones can lead to panic attacks and cardiac discomfort. 4. Cardiac arrhythmia: Cardiac arrhythmia can cause heart discomfort, such as tachyarrhythmia and conduction block. 5. Anemia: Anemia can cause a decrease in oxygen supply to the heart muscle, which can increase the load on the heart and lead to anemic heart disease. If there is no relief after resting, you should consult a doctor in time and have a reasonable diagnosis and treatment under the guidance of a professional doctor.