Getting up before dawn to exercise may not be good for your health. Some people think that the earlier the morning exercise the better, so like to go out before dawn for exercise, in fact, this is not scientific. First of all, plant chlorophyll needs to photosynthesize under the participation of sunlight, no sunlight to the leaves before the sun comes out, no photosynthesis in the night near the plant exercise, not only can not breathe fresh oxygen, but also may inhale a large amount of carbon dioxide accumulated in the vicinity of the chest tightness, dizziness, shortness of breath and other manifestations, and then gradually appeared respiratory distress and even respiratory depression. Secondly, after a night time, pollutants accumulate more in the air, breathing dirty air will have harmful effects on the human body, such as triggering bronchitis, bronchitis, asthma and other lung diseases, but also may aggravate the condition of rhinitis and sinusitis. Therefore, it is recommended that the sun comes out and then exercise, at this time, the sun to the ground, so that the atmosphere began to downward convection, the polluted air to the diffusion of high altitude, can be diluted to a certain degree of decomposition, the quality of air will be relatively good, the infringement on the human body will be reduced. And the temperature difference between morning and evening in fall and winter is large, patients with cardiovascular and cerebrovascular disease is best after breakfast 9-10 o’clock and then exercise to avoid sudden cardiovascular and cerebrovascular disease.