The best time should be at night (4-6 o'clock), and exercise before meals is better than after meals. It is not suitable for exercise in the morning, because plants can't carry out photosynthesis at night and can only release carbon dioxide, so the air in the morning is turbid. If you must exercise in the morning, it is better to do it after 10 in the morning, because the photosynthesis of plants is the strongest at 10.