When you do strenuous exercise after a meal, the blood that should have been digested will be first dispersed to the muscles of the whole body because of exercise. When there is more blood in muscles, there will be less blood in digestive organs, and less blood in gastrointestinal tissues will bring difficulties to digestion and absorption. Physiologists tell us that during strenuous exercise, sympathetic nerves are extremely excited, while parasympathetic nerves are inhibited. The secretion of digestive juice is mainly caused by parasympathetic nerve excitation, and digestion is also strengthened by parasympathetic nerve excitation. When sympathetic god is excited, digestion is inhibited and the blood vessels of digestive organs become narrow. Moreover, after eating, I take part in strenuous exercise. Because my stomach is full of food, I feel very shaken during exercise and often have abdominal pain.