The first suitable time for exercise is 9 am-10 am. Because the carbon dioxide content in the air is relatively high from 4 am to 9 am. If children often inhale such air, it will lead to chest tightness, headache, dizziness, general weakness and other symptoms. Most plants will absorb water and carbon dioxide in the air in the sun and release oxygen. But at night, without sunlight, plants will absorb oxygen and release carbon dioxide. In addition, the temperature in the morning is relatively low, and the exhaust gas emitted by motor vehicles stays in the low-level air the night before and that morning. When children exercise, their vital capacity will increase. If they inhale this polluted gas too much, it will be very harmful to their health. Therefore, it is best for children to exercise at 9: 00 am 9:00- 10/0, when the air quality is better.

The second suitable time for exercise is from 4 pm to 7 pm. This is because: from 4 pm to 5 pm, the metabolic rate of the human body will reach the peak, and at this time, the flexibility and flexibility of the body will reach the best state, which is more suitable for exercise. At 5 -6 pm, the heart rate and blood pressure will reach the most balanced state. At 6 pm, people's sense of smell, touch and vision are the most sensitive. Moreover, from 4 pm to 7 pm, the period of the strongest sunshine has passed, and outdoor sports can avoid damage to the skin at this time.