Open AccessArticle

The Effects of Dynamic and Static Forest Bathing (Shinrin-yoku) on Physiological and Psychological Health in Males and Females

Ye Wen

^1,2,

Xinren Gu

¹,

Wenping Deng

¹,

Qin Zou

³,

Yuan Hu

^2,4,

Qi Yan

¹,

Yangliu Pan

¹,

Zhaojie Wen

²,

Renhui Wan

²,

Gonghan Sheng

⁴,

Yuanqiu Liu

^1,* and

Mei He

^2,4,*

College of Forestry, Jiangxi Agricultural University, 1101 Zhimin Road, Nanchang 330045, China

Jiangxi Academy of Forestry, 1629 Fenglin Road, Nanchang 330032, China

Jiangxi Lushan National Nature Reserve, 95 Henan Road, Jiujiang 332999, China

⁴

Department of Forest Resources Management, University of British Columbia, 2329 West Mall, Vancouver, BC V6T 1Z4, Canada

Authors to whom correspondence should be addressed.

Forests 2023, 14(8), 1592; https://doi.org/10.3390/f14081592

Submission received: 11 July 2023 / Revised: 2 August 2023 / Accepted: 2 August 2023 / Published: 5 August 2023

(This article belongs to the Special Issue Forest Bathing and Forests for Public Health)

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Figure 1
Test procedures: 8:00: Participants collected and set off to the test site; 8:30: Participants arrived at the test site and performed physiological and psychological indicators; 9:00–10:00: Participants were exposed to the forest environment and hiking; 10:00: Participants assessed physiological and psychological indicators; 10:30: End of test. "> Figure 2
Test procedures: 7:30: participants collected and obtained group letters to learn their group assignment; 8:00: Test and control group arrived at the test site and underwent physiological indicators and self-assessment psychological measurements; 9:00: The test group and the control group started the test; 9:20: After the test, participants completed physiological indicators and self-assessment psychological measurements. "> Figure 3
Physiological indicators 1. 1 *: p < 0.05, **: p < 0.01, paired t-test. "> Figure 4
BPOMS scores 1, 2. 1 Abbreviations: A: Anger; C: Confusion; D: Depression; F: Fatigue; S: Self-Esteem; T: Tension; Vigor. 2 *: p < 0.05, **: p < 0.01, Wilcoxon signed-rank test. "> Figure 5
TMD scores 1. 1 *: p <0.05, Wilcoxon signed-rank test. ">

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Abstract

This study aimed to investigate the effects of dynamic and static forest bathing (Shinrin-yoku) on the physiological and psychological health of males and females. Dynamic pre-test and post-test forest bathing was performed on 11 participants (5 males and 6 females) as a single group in a forest environment. In addition, a randomized controlled trial involving 20 participants (10 males and 10 females) was conducted to evaluate static forest bathing in both forest and urban environments. Various physiological indicators, including systolic blood pressure (SBP), diastolic blood pressure (DBP), pulse, heart rate variability (HRV), and self-assessed psychological indicators such as profile of mood states, were measured. Dynamic forest bathing resulted in a significant increase in the natural logarithmic value of the high frequency (lnHF) of HRV and significantly decreased ratio of the natural logarithmic value of the low frequency (lnLF) to lnHF (lnLF/lnHF) of HRV. Static forest bathing not only had the effects of dynamic forest bathing but also significantly decreased the participants’ SBP, DBP, and pulse. Both dynamic and static forest bathing enhanced human parasympathetic nervous system activity and reduced sympathetic nervous system activity, particularly affecting females. Negative mood state scores (tension, anger, fatigue, depression, and confusion) and total mood disturbance scores significantly decreased after forest bathing. In contrast, positive mood state (vigor) scores significantly increased, indicating an enhancement in positive mood. These improvements in mood were particularly pronounced in male individuals. Short-term exposure to a forest environment has positive effects on both physical and mental health of individuals. The extent of these improvements varied according to factors such as engagement in physical activity and gender.

Keywords:

dynamic and static; forest bathing; physiological; psychological; health; gender difference

1. Introduction

Suboptimal health status (SHS) is an intermediate state between health and disease. Patients frequently experience symptoms such as chronic fatigue, insomnia, headaches, dizziness, anxiety, depression, functional system disorders, and nonspecific pain [1,2,3,4,5]. Most people with SHS have one or more of these symptoms, but the symptoms are reversible [6]. The primary risk factors for SHS include work pressure, lack of exercise, poor dietary habits, smoking, alcohol consumption, air pollution, and noise [7,8]. SHS has been observed in China, Japan, Ghana, Canada, and Australia [9]. Multiple studies indicate that approximately 55%–75% of Chinese adults are affected by SHS [7,10], with the proportion increasing with age [11]. A higher proportion of individuals with SHS are females compared with males [1,8], from rural areas compared with urban areas, and blue-collar workers compared with white-collar workers [11,12]. A suboptimal health cohort study has suggested that SHS may be an important state for the early detection and prevention of chronic diseases, but the cause of SHS and the factors that contribute to its development remain largely unknown [13]. Currently, SHS is considered a public health challenge in China and worldwide [14].

Forest bathing (Shinrin-yoku) has emerged against the backdrop of a continuously increasing SHS population globally, not only bringing a “prevention is better than cure” lifestyle approach to the population with SHS but also supplementing therapy for those already afflicted by diseases [15]. The term “forest bathing” was first used by the Ministry of Agriculture, Forestry, and Fisheries of Japan in 1982 [16], referring to a healing technique that restores human physical and mental health via “five senses experience” when exposed to a forest environment. It is the primary form of forest therapy to promote forest-based wellness activities. Forest bathing has positively impacted both human physiology and psychology [17,18], particularly in boosting immunity, treating chronic diseases, soothing mood, and reducing anxiety [19,20]. Engaging in exercise or meditation in a forest environment can be more beneficial than doing so in urban areas [21,22]. Forests positively affect human health and well-being.

As empirical research on forest bathing has deepened, medical and health experts have focused on the forest’s ability to boost immunity and reduce stress. They have found that even short-term forest bathing can help boost the body’s immune system and improve mood [23,24]. The author divides forest bathing into two modes: dynamic forest bathing and static forest bathing. Dynamic forest bathing refers to the participants being exposed to the forest environment and imposing intervention measures (e.g., mountaineering, hiking, yoga, etc.), and its effects on the human body are the result of the combined effects of environmental exposure and interventions. Static forest bathing refers to the participants being exposed to the forest environment and only experiencing nature with their body, without any intervention measures. The effect on the human body is only the effect of the environmental exposure. At present, most researchers do not distinguish between dynamic forest bathing and static forest bathing, but instead use a mix of the two models to conduct research [25]. The advantage is that it is beneficial to explore different forest bathing modes and provide a theoretical basis for the development of the forest bathing industry. The disadvantage is that it is not possible to distinguish whether the health effects result from the forest environment or intervention. In order to explore this problem, some scholars have carried out static forest bathing research. Several studies have shown that forest environmental exposure can have positive effects on physical and mental health in different genders. Middle-aged females who statically gazed at forest landscapes showed increased high frequency (lnHF) of heart rate variability (HRV) and vigor mood state, while depression, anxiety, fatigue, confusion and anger emotional states decreased [26]. Static exposure to a forest environment in young males was associated with increased vigor emotional state, decreased depression, anxiety, fatigue, confusion, and anger mood states [27], and reduced salivary cortisol concentrations. This biological indicator of stress was reduced, suggesting that the forest environment helps relieve stress in young males [28]. Some scholars have carried out dynamic forest bathing research. Hiking in a forest environment among young females enhanced the lnHF of HRV, decreased heart rate and the ratio of the natural logarithmic value of the low frequency (lnLF) to lnHF (lnLF/lnHF) of HRV, and improved vigor mood state and reduced depression, anxiety, fatigue, confusion, and anger mood states [29]. Middle-aged and elderly females hiking and making handicrafts in a forest environment could reduce their systolic blood pressure (SBP), improve their vigor mood state, and reduce their anxiety, fatigue, confusion, anger and other mood states [30]. In addition, hiking in a forest environment in middle-aged and elderly females can also reduce pulse and salivary cortisol concentrations [31]. Middle-aged and elderly males walking in a forest environment could reduce their pulse, urinary norepinephrine and urinary dopamine, improve their vigor mood state, and reduce their depression, anxiety, fatigue and confusion mood states [32,33]. Another study showed that hiking in forest environments in middle-aged and elderly males with high normal blood pressure could reduce SBP, diastolic blood pressure (DBP), urinary adrenaline and serum cortisol, and reduce mood states such as anxiety, confusion and anger [34]. These findings suggested that either static forest bathing (forest exposure) or dynamic forest bathing (forest exposure combined with physical activity) could have positive effects on physical and mental health in both male and female. However, it is still unclear whether static or dynamic forest bathing is better, what effects they have on people’s physical and mental health, and whether these effects differ according to gender. There is no research on forest bathing carried out in different-gender people under the same environment and intervention measures.

Many studies have shown that there are large differences in physical and mental health indicators between males and females. For example, in terms of physiology, males’ life expectancy is shorter than females’ worldwide [35]. In terms of psychology, males are more prone to externalized obstacles (such as attention deficit hyperactivity disorder and oppositional defiant disorder, etc.) [36]. Females are more likely to have internalization disorders (such as anxiety disorder, depression disorder, mood disorders, etc.) than males [37]. One study showed that females who were low in physical activity were nearly three times more likely to self- report depression than those who were high in physical activity, and this association was more pronounced than in males [38]. Another study found that the lockdown caused by COVID-19 had a greater psychological impact on females than on males. Compared with males, females showed more symptoms of depression, anxiety and post-traumatic stress disorder, more loneliness, and less mental well-being [39].The above shows that males and females have different feelings about the environment and exercise, which may also be the case in the process of forest bathing. Although it is known that the forest environment can positively affect physical and mental health in both males and females, the physical and mental indicators of different-gender people have to be further studied for sensitivity and response to the same environment and intervention measures.

In summary, although there is some research on forest bathing, which has revealed its positive effects on the physical and mental health of the human body, there are still some questions that are not fully explored. The mechanism of forest bathing for human health needs further clarification. The role of exercise in achieving the health benefits of forest bathing has not been explored. In addition, the role of sex on the effects of forest bathing is still unclear. Hence, this study aimed to address the aforementioned issues by conducting dynamic and static forest bathing trials, investigating the effects of exposure to forest environments combined with intervention measures on males’ and females’ physical and mental health and their health care mechanisms, and providing theoretical support for the development of the forest tourism industry.

2. Materials and Methods

2.1. Overview of Study Area and Environment

The study area, located in Nanchang Jiangxi, China, included two locations: (1) Nanchang Botanical Garden of Jiangxi Academy of Forestry (hereafter referred to as the botanical garden), which is a suburban forest with excellent natural conditions; and (2) the campus of Jiangxi Agricultural University, referred to as the university, enclosed by buildings and with almost no green plants, thus representing an urban environment.

2.1.1. Dynamic Forest Bathing

The study was conducted in the botanical garden during autumn, with clear weather conditions, air temperature from 15 ℃ to 24 ℃, and northeast winds at levels 1–2.

2.1.2. Static Forest Bathing

The study was conducted in the botanical garden and the university. The impact of forest environment exposure on human physiology and psychology was examined in the botanical garden, and the impact of urban environment exposure on human physiology and psychology was tested at the university. The study was conducted during autumn, with clear weather conditions and temperatures from 16 ℃ to 26 ℃, accompanied by northeast winds at levels 1–2.

2.2. Study Participants

2.2.1. Dynamic Forest Bathing

Participants in the Dynamic Forest Bathing trial were recruited a week before the start of the experiment through leaflet distribution and the Internet, and all participants were healthy college students or college students with mild sub-health symptoms in order to avoid underlying diseases affecting the results. A total of 12 participants were recruited, including 6 males and 6 females, of which 1 male gave up before the experiment; 11 participants participated in the dynamic forest bathing experiment. The general characteristics of the participants are listed in Table 1.

2.2.2. Static Forest Bathing

Twenty participants were recruited for this study. The recruitment time, method, and conditions for the static forest bathing experiment were the same as those for the dynamic forest bathing experiment. The participants were randomly assigned to either the forest exposure group (forest group) or the urban exposure group (city group), with each group comprising 10 participants. The general characteristics of the participants are listed in Table 2.

2.3. Experimental Data and Methods

2.3.1. Dynamic Forest Bathing

The preparation day was scheduled one day before the experiment. The participants’ basic physical parameters such as height and weight were measured, and they were informed about the experimental schedule. The participants were objectively informed about the experimental process to minimize potential psychological suggestion effects that could impact the results. The participants controlled their diet, avoided spicy food, drink, and food containing alcohol and caffeine, and stopped smoking from the preparation day.

On the day of the experiment. Participants arrived at the botanical garden at 8:00 a.m. Physiological indices and self-assessment psychological measurements were conducted at 8:30 a.m. The experiment officially started at 9:00 a.m. Participants walked along in a relatively quiet forest environment. Each participant set off one after another with an interval between 5 min and experienced a relatively quiet forest environment. The participants followed the same route with an altitude ranging 330–440 m and then returning to 330 m. The entire activity lasted for 1 h. Then, the participants rested for 30 min before physiological and psychological tests (Figure 1). To ensure the validity of the experiment, participants were prohibited from using mobile phones, wearing headphones, or using any other electronic devices. Consumption of alcoholic or caffeinated beverages, as well as smoking, was strictly prohibited. No adverse events occurred during the experiment, and participants complied with the intervention and control measures reasonably well.

2.3.2. Static Forest Bathing

The day before the experiment served as the preparation day. The height and weight of the participants were measured. They were randomly assigned into the experimental and control groups using SPSS Statistics 22.0 software. The grouping results were placed in envelopes and handed over to the participants on the day of the experiment. The participants were informed of the specific itinerary arrangements for the experimental and control groups on the day of the experiment (only an objective description of the experiment was provided, to prevent psychological suggestion effects on the participants that could affect the experiment results). The participants were instructed to control their diet starting from the preparation day, which included avoiding spicy foods, beverages containing alcohol or caffeine, and smoking.

Twenty participants received their group envelopes at 7:30 a.m. and were informed of their group assignments on the day of the experiment. The experimental group arrived at the botanical garden at 8:00 a.m. to undergo physiological index and self-assessment psychological measurements. Simultaneously, the control group arrived at the university and underwent the aforementioned measurements. The experiment officially started at 9:00 a.m. The participants in the experimental group were exposed to a forest environment and gazed at the forest area for 20 min, while the participants in the control group were exposed to an urban environment and gazed at the building for 20 min. The experiment ended at 9:20 a.m., and physiological index and self-assessment psychological measurements were conducted again (Figure 2). Electronic products such as mobile phones and personal stereos were prohibited during the experiment. Drinking beverages containing alcohol or caffeine and smoking were also prohibited. Adverse events, such as participants being bitten by mosquitoes during the experiment, occurred and possibly affected the experimental results. The participants complied with the control measures.

2.4. Detection Measures

2.4.1. Physiological Indicators

This study employed a MaiBoBo BP-37A electronic blood pressure meter (Raycome Health Technology, Shenzhen, China) to measure the SBP, DBP, and pulse data of the participants. An R211B portable electrocardiograph (Hailin Health Management Center, Bengbu, China) was used to measure the participants’ electrocardiogram (ECG) data. A series of ordered R–R Interval (RRI) data were extracted from the ECG data using the Matlab program (Mathworks, MA, USA). Kubios HRV electro cardiac signal analysis software (Kubios Oy, Kuopio, Finland) was used to further process the RRI data and obtain the HRV data.

2.4.2. Self-Assessment Psychological Indicators

The self-assessment psychological measurements were conducted using the Brief Profile of Mood States (BPOMS) developed by Grove [40], which could comprehensively reflect the participants’ mood state. The reliability index of the measurement ranged from 0.62 to 0.82, with an average of 0.71, indicating high reliability. The BPOMS consisted of 40 items, including seven mood state indicators: anger, tension, depression, fatigue, confusion, vigor, and self-esteem. The first five indicators are negative moods (negative scale; higher scores indicate worse moods), while the last two are positive moods (positive scale; higher scores indicate more positive moods). Each indicator displayed the level of the corresponding mood with the completion of the measurement by the participant. The score of the five negative mood indicators was subtracted from the score of the two positive mood indicators and then added to a constant of 100 to obtain the total mood disturbance (TMD) score, with higher TMD scores indicating more negative mood states.

2.5. Experimental Design and Analysis Methods

The experimental design for the dynamic study involved a single group pre- and post-test, while the experimental design for the static study was a randomized controlled trial (RCT). The data are presented as mean ± standard deviation. The paired samples t-test was used to analyze intra-group differences in physiological indicators in the experimental group before and after the experiment. The independent samples t-test was used to analyze inter-group differences in physiological indicators between the experimental and control groups before or after the experiment. The Wilcoxon signed-rank test was used to compare inter-group differences in psychological indicators between the experimental group and the control group before or after experiment, and intra-group differences in psychological indicators within the experimental group before and after experiment. Analysis software used SPSS Statistics 22.0. Graphs were generated using Origin 2018 software.

3. Results

3.1. Empirical Study on the Effects of Dynamic Forest Bathing on Human Physiology and Psychology

A single-group pre- and post-test design was employed for dynamic forest bathing, in which changes in physiological indicators (HRV, SBP, DBP, and pulse) and psychological indicators (anger, confusion, depression, fatigue, self-esteem, tension, vigor, and TMD) were observed before and after participants were engaged in hiking in a forest environment. The study aimed to explore the effects of forest environment exposure combined with intervention measures (physical activity) on human physiology and psychology.

3.1.1. Effects on Physiological Indicators

A significant increase in lnHF of HRV (p = 0.001 **) was observed after human exposure to forest environments via hiking, along with a significant decrease in the lnLF/lnHF of HRV (p = 0.041 *). However, no significant differences were observed in SBP, DBP, and pulse (p > 0.05) (Figure 3).

3.1.2. Effects on Self-Assessment Psychological Indicators

The results from the BPOMS indicated that exposure to forest environments during hiking improved mood states, among which the mood state indicator of anger (p = 0.008 **) displayed an extremely significant decrease, and depression (p = 0.021 *), tension (p = 0.014 *) and confusion (p = 0.012 *) displayed a significant decrease. Meanwhile, the vigor indicator showed a significant increase (p = 0.036 *) (Figure 4). The TMD score also decreased significantly (p = 0.013 *), as illustrated in Figure 5.

3.2. Empirical Study of the Effect of Static Forest Bathing on Human Physiology and Psychology

The static forest bathing test adopted an RCT design to observe changes in physiological (HRV, SBP, DBP, and pulse) and psychological indicators (anger, anxiety, depression, fatigue, self-esteem, tension, vigor, and TMD) before and after human exposure to forest and urban environments. Furthermore, this study investigated the differences between forest and urban environment exposure and explored the effects of forest and urban environment exposure (without any intervention measures) on the physiology and psychology of human beings.

3.2.1. Effects on Physiological Indicators

Inter-group comparison of the forest and city groups showed no significant differences in the various indicators between the forest and city groups before the experiment (p > 0.05), indicating that the initial values of each indicator in the two groups of participants did not affect the experimental results. After the experiment, no significant differences were observed in the various indicators between the forest and city groups (p > 0.05), as shown in Table 3.

Intra-group comparison in the forest group found that SBP (p = 0.038 *), DBP (p = 0.033 *), and the lnLF/lnHF of HRV (p = 0.002 **) decreased significantly, and pulse displayed an extremely significant decrease (p = 0.000 ***) compared with before the experiment. lnHF of HRV increased compared with that before the experiment, and the intra-group difference was significant (p = 0.002 **). Intra-group comparison of the city group found no significant difference in the various indicators after the experiment compared with those before the experiment (p > 0.05), as shown in Table 3.

3.2.2. Effects on Self-Assessment Psychological Indicators

No significant differences (p > 0.05) were observed between indicators in the forest and city groups before the experiment, indicating that the initial values of the indicators for both groups of participants would not affect the experiment’s results. Compared with the city group, the forest group showed a decrease in indicators in the mood states of anxiety, anger, fatigue, and depression, as well as in TMD score, after the experiment. Notably, differences in the anger (p = 0.012 *) and depression (p = 0.023 *) indicators reached a significant level, while those in the tension (p = 0.005 **) and fatigue (p = 0.008 **) indicators and the TMD score (p = 0.005 **) reached an extremely significant level. The vigor mood state indicator increased significantly (p = 0.042 *), as shown in Table 4.

Intra-group comparison in the forest group found that mood state indicators such as anger (p = 0.046 *), fatigue (p = 0.014 *) and depression (p = 0.024 *), as well as TMD score (p = 0.014 *), decreased significantly after the experiment. The indicator of vigor (p = 0.015 *) increased significantly. Intra-group comparison in the city group found that the fatigue (p = 0.028 *) mood state increased significantly after the experiment (Table 4).

3.3. Empirical Study on the Physiological and Psychological Effects of Forest Bathing on Males and Females

Based on these static and dynamic forest bathing experiments, this study investigated physiological (HRV, SBP, DBP, and pulse) and psychological indicators (anger, confusion, depression, fatigue, self-esteem, tension, vigor, and TMD) in different sex groups to explore the impact of forest bathing on the physical and mental health of males and females, and to identify any differences in such implications.

3.3.1. Effects on Physiological Indicators

A comprehensive study of the impact of both dynamic and static forest bathing among male participants found that lnHF of HRV increased significantly (p = 0.007 **) after the experiment. Intra-group comparison revealed that the lnLF/lnHF (p = 0.007 **) of HRV decreased significantly. Similarly, lnHF of HRV increased significantly (p = 0.000 ***) among female participants after the experiment. Intra-group comparison revealed that DBP (p = 0.041 *) and the lnLF/lnHF (p = 0.010 *) of HRV decreased significantly, as shown in Table 5.

3.3.2. Effects on Self-Assessment Psychological Indicators

Based on the comprehensive study of dynamic and static forest bathing, an intra-group comparison of male participants revealed a significant decrease in indicators of tension, anger, fatigue, and depressive mood states as well as in TMD scores after the experiment, with differences in tension (p = 0.028 *) and anger (p = 0.038 *) reaching a significant level, and those in fatigue (p = 0.005 **) and depression (p = 0.008 **) mood states and TMD scores (p = 0.005 **) reaching an extremely significant level. Further, the vigor (p = 0.007 **) mood state significantly increased, reaching an extremely significant level. Similarly, an intra-group comparison of female participants showed that anger mood state and TMD scores decreased significantly after the experiment, with the decrease in anger (p = 0.008 **) reaching an extremely significant level and that in TMD score (p = 0.033 *) reaching a significant level, as shown in Table 6.

4. Discussion

4.1. Key Mechanisms of the Impacts of Forest Bathing on Human Physical and Mental Health

Forest bathing, as a five-senses experience, positively impacts human physical and mental health. This is largely attributed to exposure to forest environments in combination with interventions such as hiking, meditation, and yoga. The main mechanism underlying the impacts of forest bathing on human physical and mental health is regulating the autonomic nervous system. The autonomic nervous system includes both sympathetic and parasympathetic systems, which govern most organ systems and work in opposition to maintain autonomic balance. When sympathetic activity is enhanced, blood pressure and pulse increase, while the lnHF of HRV decreases, the lnLF/lnHF of HRV increases, gastrointestinal motility decreases, saliva secretion decreases, and sweating increases, resulting in an activated state. Conversely, when parasympathetic activity is enhanced, blood pressure and pulse decrease, while the lnHF of HRV increases, the lnLF/lnHF of HRV decreases, gastrointestinal motility increases, saliva secretion increases, and sweating decreases, resulting in a state of calm. Most scholars believe that forest bathing can enhance parasympathetic activity and reduce sympathetic activity [29,41]. This study investigated the impacts of forest bathing on physiological and psychological health using relevant physiological indicators such as blood pressure, pulse, and HRV, which reflect human autonomic nervous system activity, as well as self-assessment psychological indicators, which reflect human mood states. After forest bathing, physiological measures such as blood pressure, pulse, and the lnLF/lnHF of HRV decreased, while lnHF of HRV increased, indicating enhanced parasympathetic activity and reduced sympathetic activity. The results of BPOMS analysis showed a decrease in negative mood and an increase in positive mood, indicating an improvement in the mood state of the human body. These findings suggested that regulating the autonomic nervous system was a key mechanism underlying the impacts of forest bathing on human physical and mental health.

4.2. Differences in Health Effects of Forest Bathing under Different Modes

Forest bathing has positive health benefits for the human body, which are mainly attributed to the combined effects of the forest environment and intervention measures. This study conducted dynamic and static forest bathing experiments to verify the effects of physical activity and inactivity under forest exposure on physical and mental health. The pre- and post-test results showed that both dynamic and static forest bathing enhanced the activity of the human parasympathetic nervous system, reduced sympathetic activity, and improved mood states. However, some differences were observed between the two types of forest bathing: (1) Changes in physiological indicators were different. Dynamic forest bathing significantly improved the lnHF of HRV in the human body and reduced the lnLF/lnHF of HRV. Although blood pressure and pulse decreased, the difference was not statistically significant. Static forest bathing significantly improved the lnHF of HRV in the human body, reduced the lnLF/lnHF of HRV, and significantly reduced blood pressure and pulse. (2) Changes in self-assessment psychological indicators were different. Dynamic forest bathing significantly improved the index of vigor and significantly reduced the indicators of tension, anger, depression, and confusion, as well as TMD score. Although the fatigue index decreased, the difference was not statistically significant. Static forest bathing significantly improved the indicator of vigor, and significantly reduced the indicators of anger, fatigue, depression and TMD score. Although static forest bathing decreased the tension index and improved the confusion index, the difference was not statistically significant. The aforementioned differences were mainly attributed to the following two reasons. (1) Impact of exercise intervention: Sympathetic nervous activity increases and parasympathetic nervous activity decreases during exercise. After exercise, parasympathetic activity increases and sympathetic activity decreases to achieve a balanced state, and forest environment exposure can accelerate this process. The dynamic forest bathing experiment did not show a significant difference in the index of fatigue mood state before and after the experiment. In contrast, the static forest bathing experiment showed a significant decrease in the index of fatigue mood state after the experiment, implying that exercise was the main factor causing this difference in the health effects of forest bathing under different modes. (2) Impact of biotic factors in the forest environment: The index of confusion mood state increased after the static forest bathing experiment compared with that before the experiment, due to adverse events of mosquito bites reported by the participants in the static forest bathing experiment. In dynamic forest bathing in the forest environment, mosquitoes are not likely to attach to the surface of the human skin for biting, which is more conducive to improving people’s emotional mood state. Studying biotic factors as an element of forest bathing is also essential.

4.3. Physiological and Psychological Response to Forest Bathing among Males and Females

Some scholars conducted empirical studies on forest bathing in different sex groups. The study by Bielinis [42] found that males and females had almost identical psychological responses to a 15-min forest bathing in winter. Guan [43] examined the effects of different forests on the psychological state of the human body and found that the level of anxiety relief in female participants in Mongolian oak (Quercus mongolica) forest was higher than that in male participants. Whether sex affects the health benefits of forest bathing needs further exploration, as studies on this topic are insufficient. Combining the results of dynamic and static forest bathing experiments, this study found the following sex-related differences in the physiological and psychological responses to forest bathing. (1) Changes in physiological indicators were different: After forest bathing, males showed a significant increase in lnHF of HRV and a significant decrease in the lnLF/lnHF of HRV compared with that before the activity; females showed a significant increase in lnHF of HRV and a significant decrease in both the lnLF/lnHF of HRV and DBP. (2) Changes in self-assessment psychological indicators were different: After forest bathing, males showed a significant decrease in mood state indicators such as tension, anger, fatigue, depression, and TMD score and a significant increase in vigor mood state indicator compared with their state before the activity. Females showed only significant decreases in anger and TMD score. On the one hand, the level of improvement from forest bathing was more significant in terms of mood state in males, and it had more positive effects on males than on females. On the other hand, the impact of forest bathing on physiological indicators in females was more significant, and the activity level of the parasympathetic nervous system was higher in females than males. The mechanism of action needs further study, which may be related to psychological safety or behavioral safety in the forest environment.

4.4. Effects of Different Environmental Exposure on Human Physiology and Psychology

Stimulation from the environment can cause different stress responses in the human body, which manifest as changes in sympathetic or parasympathetic nervous system activity. Static forest bathing experiments revealed the following: (1) Human parasympathetic nervous activity increased after the experiment more than before the experiment, indicating that the forest environment had a positive effect on human physiological indicators. No significant difference was observed in physiological indicators in the city group before and after the experiment, indicating that the urban environment did not regulate the human autonomic nervous system. (2) Regarding changes in self-assessment psychological indicators, the fatigue mood state index significantly increased in the city group after the experiment compared to before the experiment, indicating that the urban environment had a certain negative effect on the human mood state. After the forest trials, irrespective of comparison between the urban and forest groups or intra-group comparison in the forest group, individuals’ positive moods increased and negative moods decreased, indicating that the forest environment had a positive effect on human mood state. In this study, a comparison of the city and forest groups revealed no significant difference in physiological indicators after the experiment. However, BPOMS scale indicators showed that the forest environment enhanced human positive moods while the urban environment strengthened negative moods. This might be because the response of human physiological indicators to short-term forest bathing was not as fast as that of psychological indicators, requiring further studies on medium- and long-term forest bathing.

5. Conclusions

Regulating the human autonomic nervous system stands out as a key mechanism for the health benefits of forest bathing on the human body. By exposing individuals to forest environments and implementing intervention measures, forest bathing effectively enhances the activity of the parasympathetic nervous system while reducing the activity of the sympathetic nervous system. Both dynamic and static forest bathing demonstrate positive impacts on human physical and mental health, although static forest bathing shows more pronounced effects on physiological health, while dynamic forest bathing shows greater effects on mental health. Moreover, forest bathing exhibits favorable health care effects on individuals of various genders. However, it particularly increases the psychological well-being of males and the physiological well-being of females.

Our study findings highlight the potential of forest bathing as a holistic approach to promoting human well-being. The modulation of the autonomic nervous system, achieved through exposure to forest environments, plays a pivotal role in the observed health benefits. The distinct effects of static and dynamic forest bathing further emphasize the importance of tailoring interventions to target specific aspects of health. By considering gender differences, forest bathing can be personalized to address the unique physiological and psychological needs of individuals.

Our belief is that the implications of these conclusions are significant, as they support the incorporation of forest bathing practices into health care strategies. For example, healthcare professionals can leverage the therapeutic potential of forests to provide comprehensive care for their patients. Additionally, policymakers and urban planners can consider the integration of green spaces and forest environments in urban settings to enhance public health outcomes.

Overall, the evidence presented in this study underscores the value of forest bathing as a promising approach to improving human health. Further research in this field can provide deeper insights into the underlying mechanisms and refine the implementation of forest bathing interventions. By embracing the healing power of nature, we can unlock new opportunities for enhancing both our physical and mental well-being.

Author Contributions

Y.L. and X.G. conceived this study. Y.W. conducted the experiment, analyzed the data, and wrote the original paper. M.H. contributed to data acquisition and manuscript preparation. W.D., Q.Z. and Y.H. assisted in the experiment and data analysis. Q.Y., Y.P., Z.W., R.W. and G.S. assisted in the experiment. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by funds from the National Natural Science Foundation of China (No. 31660230), the Basic Research and Talent Research Project of Jiangxi Academy of Forestry (No. 2023521605), and the Mitacs and Willowest Enterprise Co., Ltd (No. FR103598).

Informed Consent Statement

The study protocol was approved by Academic Committee of Jiangxi Academy of Forestry, China. All participants gave oral informed consent.

Data Availability Statement

Due to the nature of this research, participants of this study did not agree for their data to be shared publicly, so supporting data are not available.

Acknowledgments

The authors thank all study participants.

Conflicts of Interest

The authors declare no conflict of interest.

Abbreviations

BPOMS: brief profile of mood states; DBP: diastolic blood pressure; ECG: electrocardiogram; HRV: heart rate variability; lnHF: natural logarithmic value of the high frequency; lnLF: natural logarithmic value of the low frequency; RRI: R–R interval; RCT: randomized controlled trial; SBP: systolic blood pressure; SHS: suboptimal health status; TMD: total mood disturbance.

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Figure 1. Test procedures: 8:00: Participants collected and set off to the test site; 8:30: Participants arrived at the test site and performed physiological and psychological indicators; 9:00–10:00: Participants were exposed to the forest environment and hiking; 10:00: Participants assessed physiological and psychological indicators; 10:30: End of test.

Figure 2. Test procedures: 7:30: participants collected and obtained group letters to learn their group assignment; 8:00: Test and control group arrived at the test site and underwent physiological indicators and self-assessment psychological measurements; 9:00: The test group and the control group started the test; 9:20: After the test, participants completed physiological indicators and self-assessment psychological measurements.

Figure 3. Physiological indicators ¹. ¹ *: p < 0.05, **: p < 0.01, paired t-test.

Figure 4. BPOMS scores ^{1, 2}. ¹ Abbreviations: A: Anger; C: Confusion; D: Depression; F: Fatigue; S: Self-Esteem; T: Tension; Vigor. ² *: p < 0.05, **: p < 0.01, Wilcoxon signed-rank test.

Figure 5. TMD scores ¹. ¹ *: p <0.05, Wilcoxon signed-rank test.

Table 1. General characteristics of participants in dynamic forest bathing trial (n = 11).

Characteristic	Trial Group
Average age (y)	24.64 (±1.96)
Participant (n)	Male: 5 Female: 6
Average height (cm)	168.09 (±10.21)
Average weight (kg)	62.00 (±11.78)
Average body mass index	18.34 (±2.65)

Table 2. General characteristics of participants in static forest bathing trial (n = 20).

Characteristic	Forest Group	City Group
Average age (y)	24.10 (±1.50)	23.70 (±1.00)
Participant (n)	Male: 5 Female: 5	Male: 5 Female: 5
Average height (cm)	169.30 (±7.61)	168.80 (±8.08)
Average weight (kg)	59.60 (±11.39)	57.45 (±10.15)
Average body mass index	18.10 (±3.35)	16.93 (±2.41)

Table 3. Change in physiological indexes ^1,2.

Indexes	City Group		Forest Group
Indexes	Before	After	Before	After
SBP(mmHg)	117.30 (±13.80)	112.50 (±13.89)	115.80 (±14.71)	111.10 (±13.70) *
DBP(mmHg)	74.50 (±9.11)	72.80 (±12.58)	77.20 (±11.49)	72.40 (±14.24) *
Pulse(bpm)	85.40 (±9.45)	80.80 (±9.37)	82.70 (±7.54)	73.70 (±8.64) ***
lnHF(lnms²)	5.90 (±1.61)	5.94 (±0.76)	5.60 (±0.94)	6.45 (±0.96) *
lnLF/lnHF	1.06 (±0.26)	1.12 (±0.12)	1.19 (±0.17)	1.04 (±0.20) *

¹ Comparison before and after the experiment in the city group or forest group (intra-group comparison). *: p < 0.05, ***: p < 0.001, paired t-test. ² Comparison after the experiment between the city group and forest group (inter-group comparison). There were no significant differences in all indicators, independent t-test.

Table 4. Change in psychological indexes (self-report measures) ^1,2.

Indicators	City Group		Forest Group
Indicators	Before	After	Before	After
Tension	5.50 (±3.65)	8.40 (±5.39)	3.10 (±3.14)	2.30 (±3.09)^##
Anger	4.60 (±3.92)	8.10 (±6.11)	3.00 (±3.65)	0.40 (±0.96) *^#
Fatigue	5.80 (±4.02)	10.30 (±5.16) *	8.40 (±4.03)	3.20 (±2.34) *^##
Depression	5.00 (±4.26)	6.80 (±5.53)	4.50 (±3.37)	0.90 (±2.51) *^#
Confusion	5.30 (±3.36)	3.90 (±4.88)	4.10 (±3.44)	9.20 (±5.30)
Vigor	5.60 (±3.30)	6.20 (±3.99)	5.30 (±3.30)	9.70 (±2.86) *^#
Self-Esteem	6.50 (±3.30)	3.80 (±2.78)	5.50 (±3.77)	5.50 (±3.53)
TMD	114.10 (±16.52)	127.50 (±15.45)	112.30 (±8.71)	100.80 (±7.19) *^##

¹ Comparison before and after the experiment in the city group or forest group (intra-group comparison). *: p < 0.05, Wilcoxon signed-rank test. ² Comparison after the experiment between the city group and forest group (inter-group comparison). #: p < 0.05, ##: p < 0.01, Wilcoxon signed-rank test.

Table 5. Change in physiological indexes ¹.

Indexes	Male Group		Female Group
Indexes	Before	After	Before	After
SBP (mmHg)	124.00 (±12.97)	120.60 (±13.11)	109.27 (±8.39)	106.81 (±6.33)
DBP (mmHg)	82.10 (±8.93)	82.40 (±9.68)	73.9 (±10.19)	67.72 (±9.61) *
Pulse (bpm)	81.20 (±6.17)	79.00 (±7.97)	81.36 (±9.31)	78.18 (±10.32)
lnHF (lnms²)	4.98 (±0.81)	6.12 (±0.88) **	6.17 (±0.67)	7.26 (±0.94) ***
lnLF/lnHF	1.29 (±0.17)	1.12 (±0.18) *	1.03 (±0.09)	0.93 (±0.08)*

¹ Comparison before and after the experiment in the male group or female group (intra-group comparison). *: p < 0.05, **: p < 0.01, ***: p < 0.001, paired t-test.

Table 6. Change in psychological indexes (self-report measures) ¹.

Indicators	Male group		Female group
Indicators	Before	After	Before	After
Tension	4.70 (±3.52)	2.20 (±2.82) *	4.63 (±2.97)	3.27 (±2.68)
Anger	3.50 (±5.35)	0.30 (±0.67) *	4.90 (±2.87)	0.45 (±0.93) **
Fatigue	7.80 (±4.63)	2.80 (±2.14) **	6.36 (±4.10)	4.81 (±2.31)
Depression	5.60 (±4.08)	0.50 (±1.26) **	3.72 (±3.28)	1.45 (±2.50)
Confusion	4.70 (±2.31)	5.50 (±4.79)	5.27 (±3.58)	6.27 (±5.53)
Vigor	6.80 (±3.55)	12.20 (±4.10) **	8.63 (±4.84)	10.54 (±4.76)
Self-Esteem	6.40 (±3.33)	7.00 (±4.85)	6.72 (±4.19)	6.81 (±3.51)
TMD	113.10 (±14.20)	92.10 (±8.77) **	109.54 (±13.36)	98.90 (±13.46) *

¹ Comparison before and after the experiment in the male group or female group (intra-group comparison). *: p < 0.05, **: p < 0.01, Wilcoxon signed-rank test.

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MDPI and ACS Style

Wen, Y.; Gu, X.; Deng, W.; Zou, Q.; Hu, Y.; Yan, Q.; Pan, Y.; Wen, Z.; Wan, R.; Sheng, G.; et al. The Effects of Dynamic and Static Forest Bathing (Shinrin-yoku) on Physiological and Psychological Health in Males and Females. Forests 2023, 14, 1592. https://doi.org/10.3390/f14081592

AMA Style

Wen Y, Gu X, Deng W, Zou Q, Hu Y, Yan Q, Pan Y, Wen Z, Wan R, Sheng G, et al. The Effects of Dynamic and Static Forest Bathing (Shinrin-yoku) on Physiological and Psychological Health in Males and Females. Forests. 2023; 14(8):1592. https://doi.org/10.3390/f14081592

Chicago/Turabian Style

Wen, Ye, Xinren Gu, Wenping Deng, Qin Zou, Yuan Hu, Qi Yan, Yangliu Pan, Zhaojie Wen, Renhui Wan, Gonghan Sheng, and et al. 2023. "The Effects of Dynamic and Static Forest Bathing (Shinrin-yoku) on Physiological and Psychological Health in Males and Females" Forests 14, no. 8: 1592. https://doi.org/10.3390/f14081592

APA Style

Wen, Y., Gu, X., Deng, W., Zou, Q., Hu, Y., Yan, Q., Pan, Y., Wen, Z., Wan, R., Sheng, G., Liu, Y., & He, M. (2023). The Effects of Dynamic and Static Forest Bathing (Shinrin-yoku) on Physiological and Psychological Health in Males and Females. Forests, 14(8), 1592. https://doi.org/10.3390/f14081592

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