The Effects of Exercise in Forest and Urban Environments on Sympathetic Nervous Activity of Normal Young Adults

Journal of International Medical Research, Mar 2006

In Japan, forest-air bathing and walking (shinrin-yoku) has been proposed as a health-facilitating activity in which people spend a short period of time in a forest environment. Initially, we examined the usefulness of salivary amylase activity as an indicator of an individual's stress levels in a forest environment. The circadian rhythm of salivary amylase activity was measured in healthy young male subjects under stress-free conditions. The salivary amylase activity remained relatively constant throughout the day. Salivary amylase activity was then measured before and after walking in both urban and forest environments using a hand-held monitor. Our results indicated that (i) the circadian rhythm fluctuations in salivary amylase activity were much smaller than the stressor-induced variations; (ii) salivary amylase activity was an excellent indicator of the changes in sympathetic nervous activity; and (iii) the forest was a good environment in which people could experience much less environment-derived stress.

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The Effects of Exercise in Forest and Urban Environments on Sympathetic Nervous Activity of Normal Young Adults

0 Forestry and Forest Products Research Institute , Tsukuba, Japan 1 Faculty of Engineering, University of Toyama , Toyama, Japan - >> Version of Record - Mar 1, 2006 What is This? Downloaded from imr.sagepub.com by guest on October 16, 2014 The Journal of International Medical Research 2006; 34: 152 159 The Effects of Exercise in Forest and Urban Environments on Sympathetic Nervous Activity of Normal Young Adults M YAMAGUCHI1, M DEGUCHI1 AND Y MIYAZAKI2 In Japan, forest-air bathing and walking (shinrin-yoku) has been proposed as a health-facilitating activity in which people spend a short period of time in a forest environment. Initially, we examined the usefulness of salivary amylase activity as an indicator of an individuals stress levels in a forest environment. The circadian rhythm of salivary amylase activity was measured in healthy young male subjects under stress-free conditions. The salivary amylase activity remained relatively constant throughout the day. Salivary amylase activity was then measured before and after walking in both urban and forest environments using a hand-held monitor. Our results indicated that (i) the circadian rhythm fluctuations in salivary amylase activity were much smaller than the stressor-induced variations; (ii) salivary amylase activity was an excellent indicator of the changes in sympathetic nervous activity; and (iii) the forest was a good environment in which people could experience much less environment-derived stress. Introduction During the 5 million years of human history, humans evolved to live in forest environments and it was only around 2000 years ago that we started living in urban environments. It is well known that forest environments have favourable effects on human physiological functions, and sanatoria are often built on plateaus in forest environments. There have been reports that the forest environment has excellent physiological effects on patients with allergies or respiratory diseases.1,2 Factors in the forest environment that might provide good physiological effects include the aroma of the plants,3 various environmental factors such as temperature, humidity, light intensity, wind and oxygen concentrations, and exercise performed within that environment. In contrast, people who live in an urban environment often develop diseases such as chronic fatigue syndrome. Otherwise normal healthy subjects might develop chronic fatigue syndrome due to increased fatigue and stress if they are not appropriately treated.4 To improve the quality of life of those who live in cities, it has been suggested that society develops better methods to Downloaded from imr.sagepu1b.c5om2by guest on October 16, 2014 facilitate and promote healthy activities, which can be performed in a very short period of time, are not expensive and are also enjoyable. In Japan, one such health-promoting activity is called shinrin-yoku or forest-air bathing and walking in which people attempt to spend a short period of time in a forest environment performing certain recreational activities including exercise.5,6 This health-promoting activity is expected to induce psychological relaxation in those who experience the atmosphere of the forest. However, this theory has not yet been studied scientifically with regard to the physiological effects of forest-air bathing and walking on healthy city-dwellers. In an attempt to measure quantitatively the physical and psychological status of healthy people, a variety of methods have been studied that have evaluated the activity of the autonomic nervous system using electroencephalograms (EEG), electrocardiograms (ECG), skin conductance and heart rate. However, these physical measurements have some limitations as they not only require the subjects to be restricted physically, but also require equipment that is difficult to transport. Except for heart rate monitoring, these methods cannot be used in a forest environment. The measurement of the heart rate observes the sympathetic nervous activity of the cardiovascular system and it is strongly influenced by homeostasis. In contrast, a method for measuring the sympathetic nervous system based on a biochemical marker in saliva has been investigated.7 Saliva sampling is noninvasive, making multiple sampling easy and stress free. It has been suggested that salivary amylase activity can be a useful index of plasma noradrenaline levels under a variety of stressful conditions, since it appears that increased sympathetic nervous activity is a major stimulator of amylase secretion.8,9 We have previously proposed a new method to quantify salivary amylase activity and have manufactured a handheld salivary amylase activity monitor.10,11 We investigated the physiological effects of forest-air bathing and walking as one health-promoting activity that could be used for preventive medicine. In this present study, we initially examined the circadian rhythm of salivary amylase activity in regulated stress-fr (...truncated)


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Dr M Yamaguchi, M Deguchi, Y Miyazaki. The Effects of Exercise in Forest and Urban Environments on Sympathetic Nervous Activity of Normal Young Adults, Journal of International Medical Research, 2006, pp. 152-159, 34/2, DOI: 10.1177/147323000603400204