The slow heart rate after lying down is considered to be related to the reduced excitability of the sympathetic nervous system and physiologic regulatory mechanisms. 1. Reduced excitability of the sympathetic nervous system. After lying down, all parts of the body are in a state of relaxation, while sitting is more tense, after lying down the excitability of the sympathetic nervous system is reduced, the release of catecholamines is reduced, the heart rate will slow down. 2. Physiological regulation mechanism. Lying down after the head is in a low state, to provide blood to the brain tissue when the pressure required to reduce the heart will also reduce the work done, so the reflex will cause the heart rate to slow down, belong to the physiological regulation mechanism, is not caused by disease factors. However, if the heart rate is too slow, it is recommended to consult a doctor in time to exclude disease factors.