The average heart rate of adults is 75 beats per minute, and the normal variation range is generally 60 ~ 100 beats per minute. The athlete's heart rate can be lower than 60 beats per minute when he is quiet. It is reported that the heart rate of some trained athletes can drop to 36 ~ 40 beats per minute at most, which is called sinus bradycardia in exercise physiology. Sinus bradycardia is related to training level, sports events and years of exercise. The longer the exercise period and the higher the training level, the more obvious this phenomenon is. The phenomenon of sinus bradycardia is more obvious in endurance training, long-distance running, marathon and cycling.

Sinus bradycardia in athletes is the result of increased vagal nerve tension and decreased sympathetic nerve tension during years of training, which is of positive significance to athletes' sports life. Well-trained athletes, due to sinus bradycardia, prolonged diastolic period, fully rested myocardium, avoid overwork, and have more blood filling in their hearts; At the same time, due to the athletes' long-term physical exercise, the contents of myocardial contractile protein and myoglobin increased, a large number of capillaries were born in the myocardium, and the blood supply increased. Results The myocardial fibers became thicker, the myocardial contractility increased, and the heart volume also increased. The average person's heart volume is 765 ~ 785 ml, while athletes can reach 10 15. ...