International Journal of
Environmental Research
and Public Health
Article
The Influence of Forest Resting Environments on
Stress Using Virtual Reality
Xiaobo Wang 1,2, Yaxing Shi 3, Bo Zhang 1,* and Yencheng Chiang 4
1 College of Architecture and Arts, North China University of Technology, Beijing 100144, China
2 Beijing Laboratory of Urban and Rural Ecological Environment, Beijing Municipal Education Commission,
Beijing Forestry University, Beijing 100083, China
3 Beijing Forest Well-being Planning and Design Research Co., Ltd., Beijing 100083, China
4 Department of Landscape Architecture, National Chiayi University, Chiayi City 60004, Taiwan
* Correspondence: abaodoc@ncut.edu.cn; Tel.: +86-010-88803316
Received: 13 July 2019; Accepted: 1 September 2019; Published: 5 September 2019
Abstract: To explore the effects of different types of forest environments for forest therapy, this study
focused on forest resting environments. Seven representative forest resting environments found
in field research in Beijing were used as independent variables and were shown to subjects by a
virtual reality (VR) video. Stress level was used as the dependent variable, and blood pressure, heart
rate, salivary amylase, and the Brief Profile of Mood States (BPOMS) were used as physiological
and psychological indicators. A between-subjects design was used in the experiment. A total of
96 subjects were randomly assigned to each environment type, and only one type of forest resting
environment was observed. Through the relevant sample t-test and one-way analysis of variance, the
pre- and post-test data of the indicators were analyzed. This study found that all the seven different
types of forest resting environments can produce stress relief effects to some extent. Different types of
forest resting environments have different effects on relieving stress. The most natural environment
does not have the most significant effect on stress relief. A water landscape has a positive effect on the
relief of stress. The conclusions of this study are conducive to the better use of the forest environment
for forest therapy services.
Keywords: forest; resting environment; stress; water; forest therapy
1. Introduction
1.1. Forest, Stress, and Health
In recent years, more and more studies have proved that the natural environment can promote
people’s physical and mental health [1–4]. Forests have been studied many times as typical natural
environments [5–7]. These studies directly prove or infer that the forest environment can promote
human health, perhaps through relieving stress [8].
Stress has been used multiple times as a health-related variable in many studies. Studies have
shown that long-term stress can have a negative impact and seriously affect people’s health [9–11].
Many mental disorders and cardiovascular diseases are closely related to stress [12–14]. Ulrich proposed
the theory of stress relief, from the perspective of evolutionary psychology, which states that exposure to
the natural environment can reduce stress and have a direct effect on cognitive recovery [15]. Exposure
to a real or simulated natural scene can restore a person’s psychology and physiology from stress by
enhancing positive emotions and reducing negative emotions, such as fear or anger [16]. A study has
shown that nature promotes health, mainly through four ways—air quality, physical activity, social
cohesion, and stress reduction [4].
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www.mdpi.com/journal/ijerph
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Many studies have shown that forests contribute to health. The forest environment has been
shown to be effective in relieving stress and depression and in giving psychological relief [17–20].
Studies based on the physiological effects of relaxation in the forest environment have shown that rest
in the forest can reduce cerebral blood flow in the pre-frontal cortex [5], lower blood pressure and
heart rate [21,22], increase parasympathetic activity, inhibit sympathetic activity [14,15,20,21], reduce
salivary cortisol stress hormone concentrations [21,22], and enhance the activity of natural killer cells
and anticancer proteins [6,23] to improve immune function.
1.2. Research on Different Types of Natural Environments Related to Forests
The existing research studies on forests to promote people’s physical and mental health are mostly
comparative studies of the forest environment and urban environment. Only a few studies have
investigated the recovery effects of different green environments or characteristics [24,25]. A review [26]
showed that research has involved high or low openness in the forest, with or without water in the forest,
contrasting forests and golf courses, etc. Staats et al., studied the different density and accessibility of
forest landscapes, finding that there was higher pleasure for higher accessibility and no significant
difference related to density [27]. Through interviews and questionnaires, Herzog et al., conducted a
comparative study of forests and cities with different degrees of openness. The study found that, in
the forest, high openness made people feel calm and low openness made people feel afraid, while in
cities, it was the opposite [28]. Van et al., studied park-like forest with and without a creek and found
no difference between environments with and without water [29]. Other studies have investigated
different qualities of forest environments, including the effects of different managed forest types [30],
stand density [31], and vegetation types [8].
According to the different perceived sensory dimensions (PSDs) of environments, there have
been a few studies with conflicting conclusions [24,32]. One study found that serene, rich in species,
refuge, and nature PSDs were considered to have the most recovery value and that space was also
important [33]. Another study of individuals with a stress-related mental disorder believed that
social quietness was important and that the perceived sensory dimensions seemed to be of equal
importance [34]. However, a new study in China suggested that the environment for stress recovery
would be multilayered woodlands with water, serenity, nature, less prospect, little or no culture, and a
social dimension [35].
Earlier research has shown that there are eight main characters of parks and gardens. They are
serene, wild, rich in species, space, the common, the pleasure garden, festive, culture. And all the
characters were included in the healing garden for people suffering from burnout diseases in Alnarp
(Sweden) [36].
Some studies have focused on the impacts of different landscape types in relation to forests or
woods. A study showed that urban parks, woodlands, and wild forests had more health benefits than
streetscapes [37]. In one study, four different natural landscape types for stress relief were studied,
and the results showed that exposure to the natural environment was much better than the built
environment [38]. In another, urban parks and urban forests had a similar positive impact for stress
reduction, but the urban forest seemed more positive [39]. These studies might suggest that the more
natural the environment is, the better stress relieving effect it has. More natural means the presence
of significant amounts of trees, shrubs, water, and other natural elements with minimal evidence of
human influence [38].
1.3. Forest Therapy and Resting Environment
Forest therapy has emerged in the context of research on forest health benefits. It is called
“shinrinyoku” in Japan and is developing rapidly in China. Forest therapy is a health promotion
method that is based on the forest environment and activities such as walking and rest. Forest therapy
has been proven to have a favorable influence on the health of the human body and mind in many
medical studies [40–49].
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Forest rest is one of the essential activities in forest therapy. Forest rest is an activity that involves
taking a rest in a certain place in the forest, which is compared to a forest walk in a forest bath. Forest
rest usually includes activities such as body relaxation, body scanning, and meditation. In a previous
study, the forest rest included deep breathing, abdominal breathing, lie down, and rest [42]. Contrast
experiments related to forest therapy, usually included viewing scenery in a seated position, which
was another kind of forest rest [50]. Although forest rest is rich in variety, it has similar requirements
for the environment, such as quietness and privacy. Forest therapy activities, such as forest walks and
forest sports, which are in contrast to forest rest, also require significant differences in environmental
conditions. Indeed, a multitude of activities, specifically meditation, affect the stress relief effect, but
the present study only focused on the environment of forest rest in order to assess the health benefits
of the environment itself.
The quality of the forest resting environment directly affects the effects of forest recuperation and
the experience of visitors. The forest resting environment could be chosen from many environmental
resources in the forest. However, not all natural environments have equal recovery effects. This study
tried to discover the different effects of different forest resting environments.
1.4. Application of Virtual Reality (VR) in Health- and Environment-Related Research
The definition of virtual reality (VR) is based on the concepts of “presence” and “telepresence”,
which refer to the sense of being in an environment generated by natural or mediated means [51].
It mainly includes a simulation environment, sensation and perception, natural skills, and sensing
equipment. VR can be used in many fields, such as medical, education, arts, entertainment, and
military [52].
VR is widely used in the field of health. VR has been used for motor rehabilitation [53], for the
improvement of functional recovery poststroke [54], for hand rehabilitation after a stroke [55], in the
treatment of autism [56], etc.
In the field of research related to the environment, scholars have used window views,
photos, video/videotapes, photographic slides, on-site experiences, etc. as experimental
materials [2,15,25,27,57–60]. Although there are famous, classic studies among these experiments,
VR has its unique advantages. VR technology is a big improvement in research methods, since it
gives a three-dimensional experience, which is more realistic than the two-dimensional picture or
video. At the same time, VR has better operability than exposure in a real environment. VR has the
advantages of being close to the real experience, reducing input manpower and material resources,
and can better control the independent variables. Thus, VR has the potential to be used more and more
in environment-related research [61].
1.5. Study Purpose and Hypothesis
This study focused on the impact of different types of forest resting environments on human stress
levels. The study aimed to explore the health benefits of different forest resting environments from the
perspective of stress relief. A total of 33 forest parks, almost all the municipal level of forest parks
in Beijing were field surveyed in this study. Based on site surveying, seven typical different types of
forest resting environments were found. These seven environmental types had different characteristics
in the eight PSDs. Stress-related experimental studies were conducted for these different types of
forest resting environments. The relief effects of different forest resting environments on stress were
compared and analyzed.
At present, there are few studies on different types of forest environments. As far as we know,
there have been no studies on different forest environments that specifically target forest rest.
Research on the impact of different forest environments on human health is crucial for transforming
the forest environment, carrying out forest therapy activities, and giving the public a choice of
recuperation sites. Forest rest requires the use and transformation of the environment to better utilize
the resource advantages of the forest. The development of forest therapy activities also requires
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more in-depth theoretical support so that the forest can be better utilized. At the same time, the
understanding of the health benefits of different forest environments is also important for the public to
choose the right place for recuperation. A review study indicated that research on different types of
natural environments is one of the future directions of health-related environmental research [4].
The hypotheses that guide the present research are as follows:
(1) All the seven types of forest resting environments could contribute to the relief of stress, reflected
both in the physiological and psychological index;
(2) Different forest resting environments (structure, wood, wood with bench/platform, waterfall/pool
with plants, etc.) have different effects on stress relief;
(3) The more natural factors there are, the more obvious the stress relief effect;
(4) A water landscape plays an important role in relieving stress.
2. Methods
2.1. Participants
Participants were recruited through online posting. The principles of enrollment were as follows:
aged between 18 and 35 years old and physical and mental health. At the time of recruitment, the
personal data of the participants were registered. According to the health questionnaire, 96 college
students and social workers who met the experimental requirements were selected as effective
participants, including 33 males and 63 females. The average age of all subjects was 24.03 ± 5.29 years
old, and the dominant hand was the right hand. All the subjects had normal vision or corrected normal
vision, no mental disorder, no stress disorder, no abnormal organic disease, no brain trauma, and no
endocrine diseases. This study was approved by the ethics committee of the North China University
of Technology (no. 51708003). All participants signed the experimental informed consent form before
the experiment.
2.2. Materials
The experimental material of this study were the VR images of seven forest resting environments.
Based on field research conducted in 33 forest parks in Beijing (including 15 at the national level
and 18 at the municipal level), seven different types of forest resting environments were extracted.
The landscape elements, location, characteristics, and corresponding PSDs are shown in Table 1 and
Figure 1. VR videos were filmed from May to August 2017 by a UCVR EYE-01 camera (Pinkang Smart
Company, Changzhou, China). The videos all had the same weather conditions, time, and shooting
methods. The method of shooting was to set the bracket at a height of 1.4 m from the human point
of view and fix the camera on the bracket in the same environment for 20 min at a 150◦ angle [62].
All videos were filmed in good weather conditions and showed no visitors or constructed facilities.
Every video length was 5 min, in accordance with previous studies [57,61].
Environment Type
1 (Structure)
2 (Wood)
3 (Wood with bench)
Table 1. Seven different types of forest resting environments.
Landscape Elements
Wooden pavilion,
building, wooden
platform, gravel paving,
plants, tables and chairs
Location
Outside the Forest
Experience Hall of
Beijing Badaling Forest
Park
Plants, soil
Beijing Xishan Forest
Park Forest Bath
Plants, wooden benches Beijing Badaling Forest
close to nature
Park Forest Class
Environment Features
PSDs 1
The highest degree of
artificialization,
waterless
Refuge, Social,
Space
The highest degree of
naturalization, forest
landscape, waterless
Similar to Type 2, forest
landscape, more wooden
benches, waterless
Rich in species,
Nature
Rich in species,
Nature
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Environment Type
4 (Wood with platform
and bench)
5 (Platform with trees)
6 (Waterfall with trees)
7 (Pool with plants)
Table 1. Cont.
Landscape Elements
Plants, wooden
platforms, wooden
tables and benches,
wood paving
Plants, wooden
platforms, wooden
planks, trees
Location
Beijing Baiwangshan
Forest Park Forest Bath
Beijing Xishan Forest
Park Forest Bath
Plants, pool water,
waterfall, rocks
Beijing Xishan Forest
Park entrance waterfall
Pool water, rocks, railing, Beijing Xishan Forest
fountain head, plants
Park Pool
1 Perceived Sensory Dimensions.
Environment Features
Space for performance or
podium, waterless
Independent of the rest
space of the trail,
waterless
Plants in the near-middle
prospect, hydrostatic
and hydrodynamic
Distant view has plants,
hydrostatic
PSDs 1
Social, Culture
Refuge
Rich in species,
Nature
Serene,
Prospect
(1)
(2)
(3)
(4)
(5)
(6)
(7)
Figure 1. The videos of seven different types of forest resting environments: (1) structure, (2) wood,
(3) wood with bench, (4) wood with platform and bench, (5) platform with trees, (6) waterfall with
trees, and (7) pool with plants.
2.3. Measures
2.3.1. Physiological Index
Blood Pressure and Heart Rate
Blood pressure and
level [1,63,64], especially
heart rate have usually been used
with regards to the difference in the
as indexes
data of the
ptorer-teeflsetcatnpde’tohpelep’sosstt-rteessst.
In this study, a HEM-7111 electronic sphygmomanometer (upper arm, OMRON, Dalian, China) was
used to measure blood pressure and heart rate.
There were three tests of blood pressure and heart rate, reflecting normal conditions, the high
stress state (after the Trier Social Stress Test), and the postintervention situation (after watching a
certain type of forest resting environment). Blood pressure included the systolic blood pressure (SBP)
and the diastolic blood pressure (DBP).
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Salivary Amylase
Salivary amylase is an enzyme in saliva that can hydrolyze starch, which can reflect in stress
levels. Since changes in the sympathetic nervous system can affect the secretion of salivary amylase,
salivary amylase increases as the sympathetic system is activated. Related studies have found that
salivary amylase is more rapid than hormones such as norepinephrine and cortisol and is a sensitive
indicator of sympathetic nervous system excitability [65]. A study found that during the application of
psychological stress, the salivary amylase of the subject increased [66].
This study used a professional saliva collection tube (salivette, SARSTEDT, Sarstedtstraße,
Germany) to collect the test saliva. The subjects took the absorbent cotton strips in the collection tube
and tipped them into their mouth for 1 min to collect the saliva. After chewing, the cotton strips were
spat back into the tube. Then the test tube was stored in a freezer at −18 °C. When all the experiments
were finished, the saliva was analyzed by enzyme-linked immunosorbent assay (ELISA).
Two tests of salivary amylase were performed in the experiment. The first one was to reflect the
high-pressure state after the Trier Social Stress Test (TSST). The second one was to reflect the pressure
level after watching a certain type of forest resting environment.
2.3.2. Psychological Index
Brief Profile of Mood States (BPOMS)
The Profile of Mood States (POMS) is an effective tool to research mood state which has a high
degree of reliability and validity. It is widely used in clinical, pharmacodynamics, and psychology
fields. The first version was compiled by McNair in 1971 with 65 items [67]. The Brief Profile of
Mood States (BPOMS) was a simplification and a revision of POMS with 30 items [25]. BPOMS uses a
five-point Likert scale format [26,27].
BPOMS includes five dimensions, namely tension (T), anxiety (A), fatigue (F), vigor (V), and
confusion–depression (C + D). Total mood disturbance (TMD) is an important index of BPOMS
(Equation (1)):
TMD = T + A + F + C + D − V
(1)
A high TMD score indicates a poor emotional state, there were two tests of BPOMS in this study,
just like for the tests of salivary amylase. When the participants filled in the scale, they were asked to
record their mood at that time. When they filled in the scale a second time (after watching a certain
type of forest resting environment), they were asked to imagine that they were in the environment and
could experience the real forest.
2.4. Procedure
This study used an independent group design—a between-subjects design. Participants were
randomly assigned to seven different forest resting environments. The number of participants in each
group is shown in Table 2. Each subject participated in one experiment alone to avoid interference
with each other.
Table 2. Number of participants assigned to different forest resting environments.
Environment Type
1
2
3
4
5
6
7
Total
Number of participants 15 13 12 14 12 15 15
96
This study used the Trier Social Stress Test (TSST) to increase the stress level of the subjects.
The TSST is a widely accepted laboratory psychosocial stress research paradigm [68]. In the present
study, the TSST included a 5 min public speaking and 5 min public mental arithmetic task.
Participants were asked to pay attention to some items the day before the experiment, including
eating breakfast; sleeping early; avoiding alcohol, tobacco, and rehabilitation drugs at least 24 h
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before the experiment; and avoiding intense activities or caffeine at least 12 h before the experiment.
They were not to eat any food or drink liquid (except water) for at least 1 h before the experiment.
Before the experiment, there was a brief introduction, including the purpose of the experiment, the
process and method, the risks and discomforts, and the confidentiality issues. During the experiment,
the subjects were first measured for blood pressure and heart rate as the baseline, which enabled the
subject to become familiar with the device. Then, the TSST test was conducted, and the participants
were asked to perform a 5 min public speaking and a 5 min public mental arithmetic task, which were
designed to increase the stress level of the participants. After the TSST, the pre-test was performed,
including blood pressure, heart rate, salivary amylase, and the BPOMS scale. The pre-test of each
indicator reflected the stress level at high pressure. After this, subjects were randomly assigned to
watch a VR video of a forest resting environment for 5 min, a process that was assumed to relieve
stress to some extent. Then, the post-test was carried out, in which the indicators were the same as
the previous test. The indicator data for the post-test reflected the stress level after experiencing the
intervention of a certain forest resting environment. The detailed process is shown in Figure 2.
Figure 2. Experimental process chart. VR-virtual reality; TSST-Trier Social Stress Test; BPOMS-Brief
Profile of Mood States.
During the experiment, the subjects wore second-generation VR glasses of the illusion mirror
type to watch some kind of forest resting environment. While wearing the glasses, an adjustment of
the distance between the eyes and the distance of the pupils was carried out according to individual
characteristics. After confirming that the glasses had been debugged for the best appreciation state, the
video would be timed for 5 min. During the viewing, subjects were asked to sit freely in the chair, rest
in a comfortable position according to their own habits and imagine themselves in the environment
they were watching.
2.5. Statistical Analysis
The experimental data were compiled and statistically analyzed using the software SPSS 17.0
(International Business Machines Corporation, Armonk, New York State, USA) and EXCEL 2010
(Microsoft Corporation, Redmond, Washington State, USA). First, the data were judged whether
they conformed to the normal distribution through the Q-Q diagram, and then the homogeneity
test of variance was performed. Then two main analytical methods were used: (1) for the pre- and
post-test data of the same indicator, a relevant sample t-test was performed to determine whether the
intervention of the forest resting environment played a role in relieving stress and (2) for the same
indicator, the difference of the pre- and post-test was used as the amount of change, ∆D (∆ΔD =Δpre-test –
post-–test). The ∆D wasΔanalyzed by the next two methods to determine whether there were differences
between different types of forest resting environments. For the condition that the variation satisfied
Δ
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the homogeneity of variance, a one-way ANOVA and a LSD (used for pairwise comparison) post-hoc
multicomparison were performed for the ∆D. For the condition that the variation did not satisfy the
homogeneity, a nonparametric test was performed.
3. Results
There were no missing data. We analyzed the outliers using a box plot. It was found that there
were some outliers for the pre-test and post-test values of the indicators. However, through comparison
observation, it was found that the pre-test and post-test had certain correspondence. We judged that
these outliers were not errors in measurement, recording, or experimental design. In order to maintain
the sample size and authenticity of the data, we chose to keep these outliers.
The data were analyzed, including the age, gender, baseline SBP/DBP, and heart rate. No significant
differences were found between the types of individuals. From a statistical point of view, it might be
considered that there was no difference between the individuals.
3.1. Physiological Index
Due to funding constraints, the basic measurements only collected data on blood pressure and
heart rate. The baseline data were analyzed. We found that the DBP and heart rate values between the
groups were in a normal distribution, satisfying the homogeneity of the variance, so the ANOVA test
could be performed. The results were: DBP, F (6, 89) = 1.724, p > 0.05; Heart Rate, F (6, 89) = 0.543,
p > 0.05. SBP did not satisfy the homogeneity of variance, so a nonparametric test was performed.
The results of the Kruskal–Wallis test were p > 0.05. The above results indicated that there was no
significant difference between the baseline between the groups, i.e., the physiological index of the
subjects in each group could be considered to be consistent.
The baseline and the pre-test data were compared by a related sample t-test. The results were:
SBP, t (95) = −2.242, p < 0.05; DBP, t (95) = −2.115, p < 0.05; Heart Rate (basic) − Heart Rate (pre-), t (95)
= −2.077, p < 0.05. The results showed that the pre-measurement values of blood pressure and heart
rate had increased relative to the baseline values. This showed that the TSST test had played a role in
increasing stress.
3.1.1. Comparison of Pre-Test and Post-Test
The data of the pre-test and post-test of each group were in accordance with the normal distribution
by Q-Q diagram analysis, and the homogeneity of variance was satisfied. The relevant sample t-test
could be performed.
Statistical differences were found in four types of forest resting environments between the pre-test
and post-test data. They were: Type 3, DBP, t(11) = 3.36, p < 0.05; Type 4, DBP, t(13) = 2.84, p < 0.05
and salivary amylase concentration, t(13) = 3.51, p < 0.01; Type 5, SBP, t(11) = 2.21, p = 0.05 and DBP,
t(11) = 2.51, p < 0.05; and Type 6, SBP, t(14) = 3.64, p < 0.01 and DBP, t(14) = 2.23, p < 0.05. The others
did not have statistically significant differences.
Regarding trends, only the blood pressure and heart rate of Type 1 increased, while all the other
types decreased. The post-test value of the salivary amylase concentration of Type 4 was significantly
increased (Figures 3 and 4).
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Figure 3. Pre- and post-test of blood pressure and heart rate: (1) structure, (2) wood, (3) wood with
bench, (4) wood with platform and bench, (5) platform with trees, (6) waterfall with trees, and (7) pool
with plants. Interpretation: * means p < 0.05, ** means p < 0.01.
Figure 4. Pre- and post-test of salivary amylase: (1) structure, (2) wood, (3) wood with bench, (4) wood
with platform and bench, (5) platform with trees, (6) waterfall with trees, and (7) pool with plants.
Interpretation: ** means p < 0.01.
3.1.2. Comparison of Δ∆D
The study found that the overall variance of the difference between systolic and diastolic blood
pressure was not uniform. A two-two group analysis of the data was performed. Nonparametric tests
were performed on data that did not satisfy the homogeneity of the variance, and an ANOVA was
performed on the data satisfying the homogeneity of the variance. The results showed that except for
aeonnf vtAhireNo∆nOmDVeAbnΔetwtswaTesyeppneerT1fyoaprnmed1eTday:npSdeBT6Py, pFthe(e16,∆o2Df8Δ)tah=me5oS.nB6g0P7ta,hnped<oDt0hB.e0Pr5e,snDavtBiisrPfioFendm(1te,hn2et8sh)wo=ma4so.8ng5oe4nt,espiigt<yni0ofi.f0cv5aa.nrti.aTnhcee,daantda
had
tThheegΔ∆reDatoesftSiBmPpaancdt,
DBP in different types of forest resting
where the SBP and DBP decreased the
environments was
most (Figure 5).
as
follows:
Type
6
Δ
Δ
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Figure 5. The mean of the amount of change (∆D) of systolic blood pressure (SBP) and diastolic blood
pressure (DBP): (1) structure, (2) wood, (3) wΔood with bench, (4) wood with platform and bench,
(5) platform with trees, (6) waterfall with trees, and (7) pool with plants.
The ∆D of the heart rate satisfied the homogeneity of the variance, and ANOVA and the multiple
comparisoΔns of the LSD were performed. The significant differences were as follows: Type 1 and Type
3—p < 0.05, Type 1 and Type 6—p < 0.05, and Type 1 and Type 7—p < 0.05 (Table 3).
—
—
—
Table 3. Post-hoc multiple comparison of LSD with significant differences in the heart rate of the ∆D.
Multiple Comparisons
LSD
Δ
Mean
Standard
95% Confidence Interval
Dependent Variable
Difference (I–J)
Error
Sig.
Lower
Upper
–
Bound
Bound
∆D of
Δ heart rate
1
3
6
7
−
−
−
−5.73 *
−5.27 *
−5.27 *
2.79
2.63
2.63
0.04
0.05
0.05
−−−111100−−−...255080
−−−000...001−−−338
* The mean difference is significant at the 0.05 level.
The heart rate mean value of the Δ∆D in different forest resting environments was as follows:
Type 3 reduced the most, followed by Type 6 and Type 7, and Type 1 (the pure artificial landscaping
environment) was the only type with an increased heart rate (Figure 6).
Figure 6. The mean of the ∆ΔD of heart rate: (1) structure, (2) wood, (3) wood with bench, (4) wood with
platform and bench, (5) platform with trees, (6) waterfall with trees, and (7) pool with plants.
Δ
—
—
—
Δ
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The ∆D of the salivary amylase satisfied the homogeneity of the variance, and ANOVA and
multiple comparisons of the LSD were performed. The significant differences were as follows: Type 4
and Type 3—p < 0.05, Type 4 and Type 6—p < 0.05, and Type 4 and Type 7—p = 0.01 (Table 4).
Table 4. Post-hoc multiple comparison of LSD with significant differences in the salivary amylase of
the ∆D.
Dependent Variable
Multiple Comparisons
LSD
Mean
Standard
Difference (I–J)
Error
Sig.
Pre- and post-test
salivary amylase
differences
3
4
6
7
−52.11 *
−48.22 *
−59.37 *
23.85
0.03
22.53
0.03
22.53
0.01
* The mean difference is significant at the 0.05 level.
95% Confidence Interval
Lower
Bound
Upper
Bound
−99.51
−92.99
−104.14
−4.71
−3.45
−14.60
The mean value of the ∆D of salivary amylase concentration in different forest resting environments
was as follows: Type 4 was the largest and the change was increasing, which might indicate that the
environment increased the stress, followed by Type 1 that also showed an upward trend. Furthermore,
the biggest declining trend was found in Type 7 (Figure 7).
Figure 7. The mean of tΔhe ∆D of salivary amylase: (1) structure, (2) wood, (3) wood with bench,
(4) wood with platform and bench, (5) platform with trees, (6) waterfall with trees, and (7) pool
with plants.
3.2. Psychological Index
3.2.1. Comparison of Pre-Test and Post-Test
The TMD values of all types of forest resting environments were reduced. All but Type 3 reached
a significant level, with Type 1 and Type 6 reaching a significant level of 0.01 (Figure 8).
From the changes of the five dimensions of the pre-test and post-test of the BPOMS, the dimension
values of Type 1 were significantly different; the dimension values of T and C + D of Type 2, Type 4,
and Type 5 were significantly different; the V dimension of Type 3 was significantly different; except
for the A dimension value, the other dimension values reached a 0.01 significant level; and the A and
C + D dimension values were significantly different.
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Figure 8. Pre- and post-test of total mood disturbance (TMD): (1) structure, (2) wood, (3) wood with
bench, (4) wood with platform and bench, (5) platform with trees, (6) waterfall with trees, and (7) pool
with plants. Interpretation: * means p < 0.05, ** means p < 0.01.
Regarding the trend of the pre-test and postmeasurement values, except for the V dimension value,
the dimension values reduced. For the V values, Type 1, Type 3, and Type 6 increased significantly,
while Type 4, Type 5, and Type 7 decreased (Figure 9).
Figure 9. Pre- and post-test of each dimension of the BPOMS: (1) structure, (2) wood, (3) wood with
bench, (4) wood with platform and bench, (5) platform with trees, (6) waterfall with trees, and (7) pool
with plants. Interpretation: * means p < 0.05, ** means p < 0.01.
3.2.2. Comparison of Δ∆D
The Δ∆D of the TMD and every dimension of the BPOMS were analyzed by Q-Q diagram, which
conformed to the normal distribution and satisfied the homogeneity of variance. ANOVA and multiple
comparisons of LSD after the event of the ∆D foundΔthat: for TMD, Types 1 and 3 had significant
differences; for A, Types 3 and 7 had significant differences; for V, Types 1 and 4/7, Types 3 and 4/5/7,
and Types 6 and 4/5/7 had significant differences. This was important for discovering the rules and
developing the discussion of different types. Taking TMD as an example, the LSD multiple comparison
found that there was a significant difference between Type 1 and Type 3, p < 0.05.
For the mean value of theΔ∆D, different forest resting environments had different effects on TMD
and different dimensions. For TMD, Type 1 and Type 6 had the greatest impact; for A, Type 7 had the
greatest impact and Type 3 had the smallest; and for V, Type 6 had the greatest impact, followed by
Type 3, and then Type 1, while Types 4, 5, and 7 decreased, with the trend of Type 7 being the most
obvious (Figure 10).
Δ
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Figure 10. The mean value of theΔ∆D of the BPOMS: (1) structure, (2) wood, (3) wood with bench,
(4) wood with platform and bench, (5) platform with trees, (6) waterfall with trees, and (7) pool with
plants. T——tension, A——anxiety, F2014fatigue, V——vigor, C + D——confusion-depression.
4. Discussion
4.1. All the Seven Types of Forest Resting Environments Could Relieve Stress to Some Extent
The correlation sample t-test on the pre-test and post-test values of each indicator showed that all
the seven types of forest resting environments could have certain effects on relieving stress. For Type 1
(structure), all the indicators of the BPOMS were significant and showed a positive effect on the
improvement of mood. For Type 2 (wood), significant relief effects were found in two dimensions
(tension and confusion–depression) of the BPOMS. For Type 3 (wood with bench), the diastolic
blood pressure decreased significantly, and the vigor dimension of the BPOMS increased significantly.
For Type 4 (wood with platform and bench), although the concentration of the salivary amylase
increased, the diastolic blood pressure, tension, and confusion–depression decreased significantly.
For Type 5 (platform with trees), the diastolic blood pressure, systolic blood pressure, tension, and
confusion–depression decreased significantly. For Type 6 (waterfall with trees), the diastolic blood
pressure and systolic blood pressure decreased significantly and the BPOMS index reached a significant
level of 0.01, except for the anxiety dimension. For Type 7 (pool with plants), the anxiety and
confusion–depression dimensions decreased significantly.
These results might be due to the fact that there were many plants and other natural factors in the
VR videos of the seven types of forest resting environments. This is consistent with the conclusions of
a large number of studies related to the natural environment, including stress reduction, adjustment of
emotional state, the positive relationship between the natural environment and health parameters, the
positive effect of the forest on central nervous system activity (including autonomic activity), endocrine
activity, and immune function [2,15,69–71].
4.2. Different Forest Resting Environments have Different Effects on Stress Relief
The ANOVA or nonparametric tests of the ∆D showed that different forest resting environments
had different effects on stress relief:
• On physiological indicators:
For the diastolic and systolic blood pressures, the comparison of the mean of the ∆D revealed that
there was a significant difference between Type 1 (structure) and Type 6 (waterfall with trees).
For the heart rate, the analysis of the ∆D showed that there was a significant difference between
Type 1 (structure) and Types 3 (wood with bench)/6 (waterfall with trees)/7 (pool with plants).
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For the salivary amylase, the analysis of the ∆D showed that there was a significant difference
between Type 4 (wood with platform and bench) and Types 3 (wood with bench)/6 (waterfall with
trees)/7 (pool with plants).
In summary, the stress relief effects of Type 1 (structure) and Type 4 (wood with platform and
bench) were very different from those of Type 3 (wood with bench), Type 6 (waterfall with trees), and
Type 7 (pool with plants). The former were far less effective than the latter.
Among the seven different types of forest environments, Type 1 was dominated by buildings and
structures and Type 4 had podiums/wood platforms and benches. These two types of environments
had many artificial features, especially Type 4 with its performance and podium functions, which
might lead to tension for Chinese subjects. Type 3 was a forest and had a more natural wooden bench
environment. Type 6 was a plant, rock, and waterfall environment. Type 7 was a plant, stone barge,
and pool environment. These three types of environments were more natural than Types 1 and 4.
These results were consistent with previous research that, for stress relief, the forest environment
is better than the urban environment [21,40,63], which indicates that the natural environment is more
active than the artificial environment.
• On psychological indicators:
For TMD, the comparison of the mean of the ∆D showed that there was a significant difference
between Type 1 (structure) and Types 3 (wood with bench)/4 (wood with platform and bench).
For the anxiety dimension of the BPOMS, the difference between Type 3 (wood with bench) and
Type 7 (pool with plants) was significant.
For the vigor dimension, there were significant differences between Types 1/3/6 and Types 4/5/7
and between Type 2 and Types 4/7.
Type 1 (wooden pavilion, building, wooden platform, gravel paving, plants, tables and chairs,
etc.), which had the highest degree of artificialization, decreased the total mood disturbance much
more than Type 3 (forest with wooden chairs) and Type 4 (forest with podiums/wood platforms, and
benches).
Type 7 with still water decreased the anxiety dimension much more than Type 3.
In terms of the vigor dimension, Types 1, 3, and 6, which played a similar role, caused a significant
increase. This was in stark contrast to Types 4, 5, and 7, which caused a reduction.
4.3. Not the Most Natural Forest Resting Environment Gives the Most Effective Stress Relief
It is worth noting that among the seven types of forest resting environments, the most natural
environment was Type 2 (wood) without any artificial facilities—only plants, land, and sky. However,
the results showed that, for both physiology and psychology, Type 2 was not outstanding. In addition,
it only had a significant effect on the tension and confusion–depression dimensions of the BPOMS.
For physiology, Type 3 (wood with bench), Type 5 (platform with trees), and Type 6 (waterfall
with trees) showed significance. These three types of environments all had some manual intervention.
There were wooden benches in Type 3 and a large wooden platform in Type 5. Type 6 was relatively
natural, but it was artificially natural with artificially planted plants, stacked rockeries, created
waterfalls, etc.
For psychology, Type 1 (structure) and Type 6 (waterfall with trees) were outstanding. Indeed,
Type 1 was the most artificial environment, full of buildings and structures. However, Type 1 had a
very significant effect on the regulation of emotions.
These results are in contrast to some of the conclusions that stress relief in the natural environment
is best [38,39,60,72]. However, some studies have suggested that it is not the case that the more natural
the environment is, the better the recovery effect. Historical blocks, monasteries, art galleries, shopping
centers, and coffee houses might all have a recovery effect [73–76].
According to Kaplan’s research, the environment for better recovery is rich in content [17,77]. It is
speculated that the environment with rich content might have a better effect on relieving stress. For Type
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3, besides the forest, there are wooden seats to enrich the content of the pure natural environment.
For Type 1, the content elements are abundant and refuge characteristics could be found. Perhaps
these are the reasons that explain the results.
4.4. Water Landscape Has a Positive Effect on Stress Relief
The water landscape has a positive effect on the relief of stress, but this effect cannot be generalized.
Among the seven environments, Type 6 (waterfall with trees) contained moving water and Type 7 (pool
with plants) was mainly composed of still water. Type 6 was the most prominent type of environment for
stress relief among all environments, both physically and psychologically. For Type 6, physiologically,
it caused a significant decrease in diastolic and systolic blood pressure and, psychologically, the effect of
relieving psychological stress was obvious—all except the anxiety dimension reached a significant level
of 0.01. For Type 7, physiologically, although they did not reach a significant level, blood pressure, heart
rate, and salivary amylase concentrations all showed a downward trend, with the salivary amylase
concentration declining the most among the seven types of environments. Psychologically, Type 7
was somewhat different from Type 6 and caused a significant drop in the dimensions of anxiety and
confusion–depression; additionally, the vigor dimension decreased but did not reach a significant level.
These results are evidenced by the conclusions of some previous studies. For physical and
psychological health, a “blue” gradient has been found. In self-perception, the closer to the ocean,
the more the effect of water exceeds the green environment effect [78,79]. Compared to exercising in
urban green spaces, on farmland, and in woodland environments, exercise in the environment near
water has been shown to better improve the mood [80]. Water environments, such as beaches and
rivers, have been shown to produce better mental health and low negative emotions [81]. There has
also been a study inconsistent with the conclusions of the present study. It found that there was no
difference in happiness, stress, anger, depression or tension, with or without water, in a park-like forest
environment [29].
4.5. Limitations of This Study and Future Research Direction
This study has some limitations, and should be improved in future research:
First, this study only explored the stress relief effects of seven types of forest resting environments.
These seven types were only a summary of the survey of forest parks in Beijing. In an actual situation,
the types of environments that could be used for forest therapy may be more diverse and should be
expanded much more in future research.
Second, this study found that different types of forest resting environments did have different
stress relieving effects, but the essential reasons for the differences were not found. That is, the internal
mechanism responsible for producing the different stress relieving effects was not established.
The reasons for the stress relief effect may be naturalness, comfort, beauty, familiarity, peace
of mind, spatial characteristics, etc. An in-depth study of these reasons will make the theory of
environmental health promotion clearer and more conducive to guiding actual planning and design,
which should be the focus of future research.
Third, the theoretical background for selecting the seven environments was not sufficient.
Although we quoted PSD theory, the theory was not very compatible with the seven environments.
This study analyzed the characteristics of the seven environments in various PSDs. Type 1
(structure) had “refuge, social, and space” characteristics, Types 2 (wood)/3 (wood with bench)/6
(waterfall with trees) were “rich in species and nature”, Type 4 (wood with platform and bench) had
“social and culture” characteristics, Type 5 (platform with tree) had “refuge”, and Type 7 (pool with
plants) was “serene and prospect”. In this study, with regards to the stress relief effects of various
environments, the pre-test and post-test differences of the physiological indicators of Types 2 (wood),
3 (wood with bench), and 5 (platform with trees) were significant. In addition, the pre-test and post-test
differences of the psychological indicators of Types 1 (structure) and 6 (waterfall with trees) were
significant. The stress relief effects did not establish a direct connection with the PSDs. However,
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the results of the study suggested that “refuge” (as Type 1 had) might have an important role in the
psychological relief of stress.
Future research should pay more attention to the background of the theoretical framework, and
the independent variables should be better designed and based on certain theories:
Fourth, the water landscape in this study showed some complexity for the relief of stress. The stress
relief effect of water seems to be affected by many factors. Different types of waterscapes have different
effects on relieving stress, which is worthy of further exploration in future research.
Fifth, the indicators need to be further improved. In this study, salivary amylase concentration
increased to a certain extent, which was inconsistent with previous studies. This might be related to
factors such as the small number of subjects and the distortion of watching VR video. In the future, the
sensitivity index of heart rate variability (HRV) should be added, which will make the research results
more objective.
Sixth, the visual angle of the VR video was fixed, so aesthetic fatigue might occur in the later
stages of viewing. At the same time, wearing VR glasses was not the same as the real environment
experience. In the future, field experiments should be implemented as much as possible to increase the
ecological validity of the study.
Seventh, a forest environment is a place full of the five senses—hearing, smell, taste, touch, and
sight. Additionally, air (especially phytoncide and negative oxygen ions), temperature, humidity, etc.
could also have an effect on stress in the real field. However, this study only focused on visual factors.
Other factors should be incorporated in future research.
Eighth, the specific activities for “forest rests” were ignored in this study. There are different
kinds of activities for forest rests, such as meditation and body scanning, and more activities for forest
therapy, such as walking and painting. These activities could also affect stress relief. Studies focused
on the health benefit of different kinds of activities of forest therapy are critically needed.
Ninth, most of the participants were undergraduate students and could not be representative
of the general public who participate in forest therapy. The number of participants also needs to
be increased.
5. Conclusions
• The environments for resting in the forest shown by VR video can produce stress relief effects to
some extent;
• Different types of forest resting environments have different effects on relieving stress. The artificial
environment is not as effective as the natural environment in relieving stress physiologically,
however, the artificial environment can bring about recovery psychologically;
• The forest resting environment that gives the best stress relief is not the most natural. With a
certain amount of manual intervention, the natural environment containing some facilities has the
effect of relieving stress better than the pure natural environment;
• A water landscape has a positive effect on the relief of stress, especially a dynamic water landscape,
which can play a good role in relieving stress both physically and psychologically.
Author Contributions: Writing—original draft preparation, X.W. and Y.S.; writing—review and editing, X.W. and
Y.S.; supervision, B.Z. and Y.C.; funding acquisition, X.W.
Funding: This research was funded by Special Fund for Beijing Common Construction Project. And this research
was funded by the National Natural Science Foundation of China, grant number 51708003.
Acknowledgments: Thanks to Liang Zhang and Yang Song for a lot of first-hand experimental operation work.
Conflicts of Interest: The authors declare no conflicts of interest.
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