1, the air is humid and turbid in the morning, and the ventilation in public places such as gymnasiums will not be very good (besides, people will not open the door too early). Morning exercise will bring discomfort to some people, but young people are fine, just moderate, and the elderly will have a fitness effect by walking and stretching;

2, running on an empty stomach before meals, if there is a chronic disease in the stomach, it may cause stomach cramps, or do what you can, young people have no problem.

Yes, after meals, but it's best to go one hour after meals to give your stomach a time to digest, avoid gastroptosis, and also give your intestines a time to absorb and provide energy for your exercise. After exercise and running for a period of time, pack a box of yogurt or supplement some carbohydrates, which not only ensures the balance between supply and demand of body energy, but also does not cause hunger after exercise and affect the subsequent work and life.