Breakfast should be eaten before running, because running in the morning, when the sun is not out, plants can not photosynthesize to produce oxygen, the air is dirty, the oxygen content is low, easy to suffer from respiratory diseases, running needs to consume a lot of energy, fasting can easily lead to hypoglycemia. 2 hours after breakfast, when the sun is shining, the air is fresh, the oxygen content is high, most of the food has been digested and absorbed, which can provide a lot of energy needed for running, and the blood flows into the exercise system when running, which will not cause discomfort of the consumption system, so breakfast should be eaten before running.