The effects of exercise in forest and urban environments on sympathetic nervous activity of normal young adults

J Int Med Res. Mar-Apr 2006;34(2):152-9. doi: 10.1177/147323000603400204.


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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Amylases / metabolism
  • Circadian Rhythm / physiology
  • Exercise / physiology*
  • Humans
  • Japan
  • Male
  • Rural Health
  • Saliva / enzymology
  • Stress, Physiological / enzymology
  • Sympathetic Nervous System / physiology*
  • Trees
  • Urban Health


  • Amylases