Walnut trees are planted all over China, and some cities are used as shelterbelts for road greening; Because its wood is tough and elastic, and it is also a first-class material used in industry, it is ok to exercise under the walnut tree, but it is best to exercise in the sun. Generally speaking, plants inhale oxygen and spit out carbon dioxide at night, and the surface air is dirty. As the sun rises, the air quality will change. Moreover, physical indicators are also rising, and exercise is unsafe. In addition, exercise is not recommended at noon, and you should rest for half an hour. The best time is 16 to 19.