Winter outdoor temperature is low, the time of the morning run should not be too early, otherwise it is easy to catch a cold, and the morning air quality is not good, it is recommended that the winter morning run between 9-10 a.m., this time is more suitable for exercise. In winter, before sunrise, the outdoor temperature is very low, the carbon monoxide and carbon dioxide content released in the air is high, the air is not fresh, while the car emissions and heavy metals in the air, in the morning are more active, more likely to enter the human respiratory tract. Therefore, the time of the morning run should not be too early, the best time for the winter morning run between 9-10 a.m., when the temperature is more suitable, as the temperature rises the air began to flow, the harmful gases in the air began to gradually sink, when the morning run is more conducive to health. In addition, if the winter morning running time is too early, the harmful gases in the air will invade the respiratory tract, long-term can cause laryngitis, not conducive to respiratory health.