Excessive exercise before going to bed excites the brain, which is not conducive to improving sleep quality. Professor Hu Yang from the Department of Biochemistry, Beijing Sport University said in an interview that Japanese scholars think that bedtime exercise can promote sleep quality recently. Experiments show that people's sleep quality is closely related to rectal temperature. The faster the rectal temperature drops, the easier it is for people to fall into deep sleep. Studies have found that doing some light exercise such as jogging before going to bed can promote the temperature rise. When the body is slightly sweaty after jogging (this exercise time varies from person to person, generally speaking, 20-30 minutes is appropriate), then stop. At this time, the body temperature began to drop. When sleeping after 30-40 minutes, people will easily fall into deep sleep, thus improving the quality of sleep. Nowadays, many professional athletes like to do massage before going to bed, which proves the reliability of this view psychologically and physically. The popular folk saying "take a hot bath (feet) before going to bed and have a comfortable sleep" also accords with this new view.

So when is the best time to exercise?

Avoid the air pollution peak at six or seven in the morning in the first month or two of winter and spring.

In summer and autumn, the sun comes out early and you can exercise at five or six o'clock.

Usually, you can choose 10 in the morning, do exercises at 3 or 4 pm or do other sports. At this time, the air is cleaner and more beneficial to health.

It is best not to exercise outdoors in foggy mornings. Due to air pollution, fog contains many substances harmful to human body. When people do strenuous activities such as long-distance running in foggy days, some sensitive parts of the body will come into contact with these harmful substances and be inhaled in large quantities, which may easily cause tracheitis, laryngitis, conjunctivitis and allergic diseases. So on foggy mornings, we can do morning exercises indoors instead of going outdoors.