Fresh air is defined as cool, unpolluted air in natural surroundings. It certainly doesn't exist everywhere. In China the air in some cities is so polluted that bags of "fresh air" are taken there so people can take a breath of it.
In enclosed rooms, air soon loses oxygen. When you sit at a desk, your breathing is shallow and superficial. That results in fatigue and lack of concentration. Exercising in the fresh air, in contrast, causes us to breathe deeply. We take in more oxygen and expel stale air from our lungs. That results in more energy and a better mood. And it even works in bad weather! If you feel listless and worn out, get out in the fresh air and greenery!
Korean doctors sent 43 elderly women on an hour-long walk in the woods and19 through the town. Examinations before and afterwards showed that the blood pressure of those who walked through the woods was lowered considerably. The elasticity of their arteries had improved. Those who walked in an urban environment. in contrast, showed no differences. A study in Japan has also shown that walks through the woods lowered blood pressure and heart rates and reduced stress hormones. In addition, the Nippon Medical School in Tokyo found signs that walking in the woods activated natural killer cells, a component of the immune system that fights cancer.