Forest-bathing and physical activity as weapons against COVID-19: a review.

Strengthening the immune system in order to better withstand the threat of COVID-19 is an important way to ensure the protection of our health against the current pandemic associated with SARS-CoV-2. There are many ways to achieve this, but with current circumstances, certain modalities stand out as being the most valid and are certainly worth greater consideration. Here we review the effects that particular immuno-strengthening activities can have on limiting the severity of COVID-19 disease as well as preventing virus infection. Physical activity, in particular, should not be discounted as an important method of prevention of viral diseases as it triggers many biological processes within the human body which in turn lead to heightened natural defences against viral infections. When exercise is performed in forested areas, these protective health benefits may be increased since many plant species emit biogenic volatile compounds (VOCs) which, when inhaled, have many protective properties. These VOCs have been shown in particular to have immunostimulatory effects on the human body and, thus, they could be of use in the prevention and/or treatment of COVID-19. Being amongst trees may also help to alleviate stress and anxiety, lowering cortisol levels and consequently helping the proper functioning of the immune system. In the following work, we have performed an analysis of the available scientific literature which looks at the effects of physical exercise as well as 'forest-bathing' on the immune system's ability to fight disease, especially of course as it relates to COVID-19. Our review aims at shedding light on the benefits of exercising outdoors in green areas and suggests reforestation as a protective measure against future outbreaks.