1. Introduction
inflammation
INFLAMMATION
There is a considerable body of evidence on sustaining health benefits of being active and a scientific consensus that physical activity—in adequate dosage—should be used in the promotion, maintenance and recovering of physical as well as mental health [In order to promote the enjoyment of physical activity and, thus, encourage adherence and support a healthy lifespan for all individuals, it is important to consider different lifestyles [Clinically relevant health benefits for a wide range of conditions could be achieved at levels of physical activity clearly below current international recommendations (e.g., least 150 min of weekly moderate to vigorous physical activity) [Therefore, effective lifestyle interventions should take an integrated approach to health and promote the importance of healthy lifestyles such as reducing sedentary time and increasing physical activity, additionally promoting healthy eating as well as managing stress [Further, evidence shows that exposure to immunoregulatory microorganisms (“Old Friends”) is essential for humans to decrease immune (re)activity and inflammation [Additionally, predominantly in high-income countries, a significant decline in physical activity has been observed (insufficient activity in 2001: 31.6%, in 2016: 36.8%). Globally, more than a quarter of the population has insufficient levels of physical activity. Furthermore, beyond reduced contact with nature, urbanization thus leads to lifestyle changes as work and leisure activities shift indoors, encouraging inactive or sedentary behavior [A possible approach to reconnect with nature and “Old Friends” as well as to increase physical activity, could be Green Exercise. This means exercise in nature, as it is the case in particular with mountain hiking or, in a less intensive form, with forest therapy. Mountain hiking can be described as a long-lasting activity of moderate intensity at different altitudes [Likewise, the positive effect of nature and its specific elements on human health is the essential component of forest therapy: This approach of nature connection therapy, also known as “forest bathing”/”Shinrin-Yoku”, is a collective term for activities designed to improve human health or well-being in a forest environment. The crucial element of forest therapy is recognition for the forest environment using the five human senses, which can be combined with meditation, breathing exercises, forest walks, various recreational activities, and cognitive behavioral therapy [Forest therapy has been shown to be effective in improving immune function; a hypothesis for this is that the forest biodiversity and microbiome has a significant impact; more precisely, phytoncides from trees can reverse stress-induced immunosuppression and thus, normalize immune function and neuroendocrine hormone levels [Although, there are further studies on positive health effects of forests [The purpose of the ANKER-study (“Algund Nature and Climate Therapy: Green Exercise vs. Nature Connection”) is to investigate long-term effects of two types of nature-based therapies—mountain hiking vs. forest therapy—in couples with a sedentary lifestyle on health-related quality of life (HRQOL), relationship quality and other psychological and physiological parameters.