International researchers have now confirmed that walking in the forest — compared to walking in an urban setting — produces medicinal benefits.
The researchers, from Finland, Japan and Korea, compared the effects of walking among 48 healthy adult men. During their enlistment process, the researchers excluded smokers and anyone diagnosed with heart disease, allergies or mental conditions from the study. During the two days of the study, the remaining 48 men did not drink alcohol, exercise vigorously nor smoke.
The researchers utilized a physiological parameter called heart rate variability. This was measured by portable electrocardiograph machine (ECG). The ECG allows researchers to measure autonomic nervous activity.
Measurement of high frequency and low frequency heart rate variability levels were also measured to indicate sympathetic nervous activity. Heart rate frequency measurements were recorded while the subjects were walking. These frequency measurements indicate metabolic health and nervous condition — anxiety and stress.
In addition, the researchers measured blood pressure using a portable blood pressure monitor. Blood pressure readings were taken three times during each walk, and before and after each walk.
Questionnaires were also given to the subjects to measure their moods and psychological conditions. In all there were four questionnaires given. Scales used included the Profile of Mood States (POMS) index and the Spielberger State-Trait Anxiety Inventory (STAI) index.
The walking test protocol
The test subjects walked at their own pace, among forest environments that included four different locations in Japan. Each forest walk was matched with an urban walk in the same region. The walks were all more or less flat, and the walking distances were the same.
Each walk lasted from twelve to fifteen minutes. The groups were randomly split and half walked in the forest and the other half walked in the urban center. The next day, the forest group walked in the urban center and the urban group took the forest walk.
The researchers found that the walking speeds between the forest walks and the urban walks were about the same.
High-frequency heart rate variability — also called HF-HRV – indicates fluctuations of the heart’s rhythms that illustrate general health. Low High-frequency heart rate variability has been seen among those with higher anxiety, reduced cardiovascular health, and tendencies toward depression and hostility according to previous research. Research has also found greater high-frequency HRV scores relate to better sleep.
The results were significant
This study found that while the forest and the urban walks took the same length of time and were physiologically the same, the forest walk resulted in significantly higher levels of high-frequency heart rate variability.
Heart rates were also significantly lower during the forest walks compared to the urban walks. The average heart rates during the forest walk were 87 BPM (beats per minute) while the urban walk average was nearly 92 BPM.
And systolic blood pressure during the forest walk was significantly lower than during the urban walk. Blood pressure during the forest walk averaged 114 mmHg and averaged 116 mmHg during the urban walk.
Note that these are among the same people taking two similar walks — the only difference being the surrounding of each walk.
Regarding the questionnaires, the forest walks resulted in significantly better scores among the men. This included the tension-anxiety score — 36 versus 42 points; the anger-hostility score — 37.7 versus 39 points; fatigue — 36 versus 41; and confusion — 42 versus 44.
The forest walking also “refreshed” the subjects more than the urban walk did — with a score of 65 versus 50.
The researchers also stated:
“Subjective evaluation using the SD method revealed that the participants felt more comfortable, soothed, and natural after forest walking than after urban walking both before and after activities.”
One of the most meaningful differences was in the anxiety levels. The forest walkers scored 33 after the walk, while the urban walkers scored 45 on the anxiety scale.
In their discussion, the researchers concluded:
“We performed field experiments in four different local areas to evaluate the physiological benefits of forest walking. Our data indicated that the forest walking program has a positive influence on cardiovascular relaxation.”
The researchers added that the benefits of forest walkers compare favorably with those that have been accomplished with research on meditation:
“These trends in heart rate variability response are often detected in meditation or yoga therapies.”
These results are consistent with those found in meditation studies
Several studies have compared meditation and heart rate variability and frequency. For example, one study published in 2004 followed 22 healthy adults who had not meditated previously. They submitted to zen meditation, and during their meditation their high frequency heart rate variability levels increased significantly, just as was found in this forest walking study.
Most of us have found nature to be calming and soothing compared to taking a trip through the urban jungle. Nature has a way of synchronizing with our bodies and minds.
Juyoung Lee, Yuko Tsunetsugu, Norimasa Takayama, et al., “Influence of Forest therapy on Cardiovascular Relaxation in Young Adults,” Evidence-Based Complementary and Alternative Medicine, vol. 2014, Article ID 834360, 7 pages, 2014. doi:10.1155/2014/834360
Murata T, Takahashi T, Hamada T, Omori M, Kosaka H, Yoshida H, Wada Y. Individual trait anxiety levels characterizing the properties of zen meditation. Neuropsychobiology. 2004;50(2):189-94. http://www.karger.com/?DOI=10.1159/000079113
Tobaldini E, Nobili L, Strada S, Casali KR, Braghiroli A, Montano N. Heart rate variability in normal and pathological sleep. Front Physiol. 2013 Oct 16;4:294. http://dx.doi.org/10.3389/fphys.2013.00294