The fluctuating and beating sensation in the abdomen is due to the beating process of the abdominal aorta, which makes it easy for the receptors on the body to feel the beating sensation. There are two main reasons why the pulsation of the abdominal aorta can be felt at this time: First, the pulsation of the abdominal aorta is increased when the sympathetic nerves are excited, such as after strenuous exercise, the cardiac output increases, and the pulsation of the abdominal aorta increases along with it. So the pounding sensation is very strong, which is caused by sympathetic excitement at this time. Another situation is that when the body is thin or lying down, the skin of the abdomen is in a state of tension, which can make their sensory function enhanced. It is possible that in this position, the sensation of being able to feel the pulsation of the abdominal aorta is very strong. Therefore, once the abdominal artery beating sensation appears in the abdomen, it is possible that the sympathetic nerves and abdominal muscles have become tense.