Erin Largo-Wight, PhD 1, Brian K. O Hara, MD 2, and W. William Chen, PhD 3. Introduction. Research

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1 Research Health Environments Research &DesignJournal 2016, Vol. 10(1) ª The Author(s) 2016 Reprints and permission: sagepub.com/journalspermissions.nav DOI: / herd.sagepub.com The Efficacy of a Brief Nature Sound Intervention on Muscle Tension, Pulse Rate, and Self- Reported Stress: Nature Contact Micro-Break in an Office or Waiting Room Erin Largo-Wight, PhD 1, Brian K. O Hara, MD 2, and W. William Chen, PhD 3 Abstract Background: There is a growing recognition that environmental design impacts health and well-being. Nature contact is a design feature or exposure that is especially important in public health and healthcare. To date, there are limited findings on the impact of nature sounds. Objective: This experimental study was designed to examine the effect of nature sounds on physiological and psychological stress. Methods: Participants were randomized into one of three groups silence (n ¼ 9), nature sound (n ¼ 17), and classical music (n ¼ 14) and listened to the assigned sound for 15 min in an office or waiting room-like environment. Pre- and postdata were collected including muscle tension (electromyogram), pulse rate, and self-reported stress. Results: With the exception of pulse rate, there were no statistical differences in baseline or demographics among groups. A paired t-test by group showed a decrease in muscle tension, pulse rate, and self-reported stress in the nature group and no significant differences in the control or the classical music groups. The significant reduction in muscle tension occurred at least by 7 min of listening to the nature sound. Conclusion: This study highlights the potential benefit of even very brief (less than 7 min) exposure to nature sounds. Brief nature sound booster breaks are a promising area for future research with important practical implications. Keywords nature contact, stress reduction, wellness by design, evidenced-based environmental design, public health, office, waiting room Introduction There is a growing recognition that environmental design impacts health and well-being (Frumkin, 2003). Creating environments with natural elements to promote well-being is both intuitive and scientific (Frumkin, 2001; Northridge, Sclar, & Biswas, 2003; Parsons, 1991; Regan & Horn, 2005). Nature contact is a design feature or 1 Department of Public Health, University of North Florida, Jacksonville, FL, USA 2 Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN, USA 3 Department of Health Education and Behavior, University of Florida, Gainesville, FL, USA Corresponding Author: Erin Largo-Wight, PhD, Department of Public Health, University of North Florida, 1 UNF Drive, Jacksonville, FL 32224, USA. largo.wight@unf.edu

2 46 Health Environments Research & Design Journal 10(1) exposure that is especially important in public health, and past research findings have shown a consistent correlation between nature contact exposure and health outcomes. Nature contact exposure has been associated with reduced stress, improved attention, improved recovery following surgery, and enhanced well-being among many populations including children, adult, employees, and patients. Most of the previous applied research has taken place in healthcare or workplace settings and focused on indoor features such as window view, natural sunlight, and plants (Bratman, Daily, Levy, & Gross, 2015; Huisman, Morales, van Hoof, & Kort, 2012; Largo-Wight, 2011; Shanahan et al., 2015). Nature contact is a design feature or exposure that is especially important in public health. The theoretical framework to understand how nature contact improves health has been the focus of research inquiry among multiple disciplines. For decades, biology researchers have explored human evolution as it relates to healthful environments. The biophilia hypothesis contends that natural elements are calming for people today because of the linkage to survival in the past (just as common fears snakes, spiders, heights are rooted in the past related to survival; Buss, 1995; Wilson, 1984). Throughout human existence, human biology has been embedded in the natural environment. Those who could smell the water, find the plants, follow the animals, and recognize the safe havens, must have enjoyed survival advantages. (Frumkin, 2001, p. 235). In addition, researchers have studied the brain and stress response after exposure to natural elements and developed Environmental Restoration Theory (ERT). ERT is a theoretical framework to explain how natural elements reduce stress and promote health in people today, and exposure to natural elements appears to enhance or restore coping resources to modify the stresscoping balance in favor of coping and health and/or stimulate underutilized portions of the brain, which may also relieve fatigued areas of the brain (Kaplan, 1995; Ulrich, 1991). ERT is a theoretical framework to explain how natural elements reduce stress and promote health in people today. The focus of this study is on less studied nature contact exposure nature sounds. There have been limited findings on the impact of nature sounds on stress and health, but the few published findings suggest that nature sounds may be a healthful exposure (Annerstedt et al, 2013; Diette, Lechtzin, Haponik, Devrotes, & Rubin, 2003; Largo-Wight, Chen, Dodd, & Weiler, 2011; Ulrich, Simons, & Miles, 2003). For example, in a 2013 study, participants exposed to a simulated forest environment with nature sounds had a significant reduction in cardiovascular stress markers and cortisol levels following an induced stressor (Annerstedt et al., 2013). Similarly, in a healthcare setting, blood donors who viewed a nature scene video had significantly lower blood pressure and pulse rate than participants who viewed other videos (daytime TV or urban scene; Ulrich et al., 2003). In another study, researchers found that patients exposed to a large nature scene printed on the bedside curtain and recordings of flowing stream and birds chirping during a bronchoscopy procedure showed a 43% increase in the self-reported pain control compared to the control group (Diette et al., 2003). There have been limited findings on the impact of nature sounds on stress and health, but the few published findings suggest that nature sounds may be a healthful exposure. These studies suggest that nature sounds, along with nature visuals or videos, have impacted physiological and/or self-reported stress. To date, there is a no known research on the effect of nature sound alone on health-related outcomes. This experimental study was designed to examine the effect of nature sounds on physiological and self-reported stress by comparing three groups nature sounds, classical music, and silence.

3 Largo-Wight et al. 47 Table 1. Results are Displayed as Mean (Standard Deviation). Control Nature Sounds Classical Music Pre-EMG 5.7 (2.6) 7.3 (4.3) 6.0 (3.9) Post-EMG 5.1 (1.9) 5.1 (2.1) 6.2 (3.6) ~EMG Pre-Pulse 73.7 (6.9) 79.4 (10.7) 69.8 (9.0) Post-Pulse 73.6 (5.3) 75.5 (8.7) 68.6 (9.7) ~Pulse Pre-Stress 2.9 (0.8) 3.3 (1.8) 3.4 (1.3) Post-Stress 2.3 (1.1) 2.3 (1.2) 2.6 (1.2) ~Stress Note. ~ denotes change in scores from pretest to posttest. This experimental study was designed to examine the effect of nature sounds on physiological and self-reported stress by comparing three groups nature sounds, classical music, and silence. Methods University IRB approval was obtained, and participants issued written informed consent before any data were collected. A convenience sample of 45 college students volunteered to participate in this experimental study. Five participants were not included in the study because of technical concerns with the equipment (N ¼ 40). Participants were blinded to the purpose of the study and randomized into one of the following groups: silence (n ¼ 9), nature sound (n ¼ 17), and classical music (n ¼ 14). See Table 1 for demographics and baseline scores of groups. The silence group served as the control and the classical music group served as the comparison previous findings have shown that music, especially classical music, reduced stress (Chafin, Roy, Gerin, & Christenfeld, 2004; Pelletier, 2004; Scheufele, 2000). Upon arrival to the laboratory, the participant was given an introductory overview of the procedures and then asked to review and sign the informed consent form. After approximately 10 min of resting, researchers collected baseline measurements including baseline muscle tension (electromyogram [EMG]), pulse rate, and selfreported stress. The EMG and pulse rate methods used in this study are institutionalized psychophysiological measures of stress. Muscle tension was measured with an EMG. Three electrodes were placed on the skin of the forehead muscles (frontalis), and an average muscle tension reading over 2 min was recorded. The frontalis placement was used because EMG activity of the forehead muscles represents a well-established measure of stress and tension (e.g., Cacioppo, Tassinary, & Bernsten, 2007). Heart rate was measured and averaged over 1 min. Similarly, this measure of heart rate variability has been long recognized as an index of perceived stress (e.g., Steptoe, 2007). Self-reported stress level was measured by asking the participant: How do you feel right now from 1-10 with 1 being totally relaxed and calm and 10 being totally stressed and anxious? This is a commonly used method of self-reported stress measurement, and perceived stress has frequently been measured with a single item self-report question with response options on a 10-point scale with anchors (e.g., such as tension/ calm or relaxed/anxious; Ahlstrom, Grimby-Ekman, Hagberg, & Dellve, 2010; Elo, Leppanen, & Jahkola, 2003; Shapiro, Astin, Bishop, & Cordova, 2005; Thomee, Harenstam, & Hagberg, 2011). The intervention consisted of listening to sounds on headphones for a brief 15-min intervention. Participants in the nature sound group listened to sounds of ocean waves, the classical music group listened to Mozart, and the control group listened to nothing (silence). Ocean waves were the nature sounds selected in this study because they are widely used in commercial products for stress reduction, and they have been previously studied with promising findings (Bugbee et al., 2005). Classical music was used as a comparison condition for the nature contact treatment condition because music, especially classical music, has consistently shown to have stressreducing effects in the past findings (Bugbee et al., 2005; Burns, Labbe, Williams, & McCall, 1999; Chafin et al., 2004; Krout, 2007; LaCrusia & Parker, 2011; Linnemann, Ditzen, Strahler, Doerr, & Nater, 2015; Pelletier, 2004). Silence was used as the control condition.

4 48 Health Environments Research & Design Journal 10(1) Mean 5.0 Pre EMG Post EMG Half EMG 4.5 control nature classical music Figure 1. Nature sound group pretest electromyogram (EMG), half-way EMG, and posttest EMG. All participants sat at a desk and faced a plain, white wall, similar to an office environment or waiting room, during the 15-min intervention. The 15-min duration and the setting were used because of the promise of brief stress-reducing interventions. Past studies have used this brief duration (10 15 min) of health intervention (e.g., Scheufele, 2000) to assess the impact of a booster break (Hartig, 2006) or micro break (Lee, Williams, Sargent, Williams, & Johnson, 2015) on health and stress among participants. This duration may also be practical because it mirrors the duration of a standard work break and the average time in the waiting room for primary care, which may be practical settings and implication for these findings (Bratman et al., 2015; Gignon, Idris, Manaouil, & Ganry, 2012; Largo- Wight et al., 2011; Lee et al., 2015; Ward & Hawthorne, 1994). Self-reported stress, muscle tension, and pulse rate were collected at baseline before the 15-min intervention (pretest) and after the intervention (posttest). In addition, muscle tension was recorded at 7 min into the intervention ( halfway EMG ) to assess the impact of duration. Results There were no statistically significant differences in demographic variables (age, sex, ethnicity, grade point average, and university classification) among groups. The sample was 87.5% females (n ¼ 35) and primarily non-hispanic white 62.5% (n ¼ 25) with a mean age of 22 (SD ¼ 5.3). Approximately half of the participants reported junior university classification (n ¼ 18) and the other half (n ¼ 22) participants reported senior university classification. A one-way analysis of variance (ANOVA) and Tukey post hoc revealed that there were no significant differences among groups in the baseline self-reported stress or baseline EMG levels. However, despite randomization, there was a statistically significant difference among groups in baseline pulse rate, and nature sound group had statistically higher average baseline pulse rate than the classical music group (p <.05). A between-group, one-way ANOVA revealed there were no significant differences in pulse rate, EMG, or self-reported stress change scores from pretest to posttest among the groups. However, withingroup analyses revealed significant stress reduction within the nature group. A paired t-test analysis with a split file for group revealed significant differences between pre- and postmeasures in the nature sound group. The nature sound group showed a significant decrease in muscle tension in the posttest EMG and half-way EMG (M ¼ 5.6, SD ¼ 2.7), recorded at 7 min into the intervention, compared to the pretest EMG (p <.05). In addition, the nature sound group showed a significant decrease in pulse rate selfreported stress after the nature sound intervention (p

5 Largo-Wight et al. 49 <.01; see Table 1). There were no significant pre post differences in the control group or the classical music group in any of the outcomes. The nature sound group was the only group that experienced significant reduction in stress from pretest to posttest in the three outcome measures. The nature sound group showed a significant decrease in muscle tension in the posttest EMG and half-way EMG (M ¼ 5.6, SD ¼ 2.7), recorded at 7 min into the intervention, compared to the pretest EMG (p <.05). In addition, the nature sound group showed a significant decrease in pulse rate self-reported stress after the nature sound intervention. The nature sound group was the only group that experienced significant reduction in stress from pretest to posttest in the three outcome measures. In addition, and importantly for implications for practice, there were no significant differences between half-way EMG (at 7 min) and post-emg (at 15 min) in any group (see Figure 1). Conclusion The lack of significance in change scores among groups may reflect the relative small unit of change, the convenience sample, and group sizes. These are noted limitations of this study. However, it should be reinforced that although there were no significant differences in comparisons among groups, there were significant differences within groups. After each group s individual analysis of pretest and posttest scores, we found that only the nature sound group had significant reduction in stress in all three outcomes from pretest to posttest. In the nature sound group alone, there were significant decreases in facial muscle tension, pulse rate, and self-reported stress. These findings support previous nature contact findings (Annerstedt et al., 2013; Diette et al., 2003; Frumkin, 2003; Largo-Wight, 2011; Shanahan et al., 2015; Ulrich et al., 2003) and suggest that listening to nature sounds may reduce stress. Further, listening to both nothing and Mozart did not promote significant decrease in physiological and self-reported stress. In fact, contrary to former findings on the impact of music on stress reduction, there was no significant decrease in pulse rate, muscle tension, or self-reported stress in the classical music group. In fact, there was a mean increase in muscle tension in the classical music group. This finding may reflect musical preference of the participants (Burns et al., 1999; Linnemann et al., 2015; Pelletier, 2004) and further supports the promise of the nature sounds for stress reduction. After each group s individual analysis of pretest and posttest scores, we found that only the nature sound group had significant reduction in stress in all three outcomes from pretest to posttest. In the nature sound group alone, there were significant decreases in facial muscle tension, pulse rate, and self-reported stress. In addition, the lack of significant difference between half-way EMG taken at 7 min and posttest EMG was important. These findings suggest that 7- and 15-min interventions resulted in no difference in reducing facial muscle tension. These findings warrant future research. Brief nature sound mini-intervention, or what has been called a nature contact booster break (Hartig, 2006) or micro break (Bratman et al., 2015; Lee et al., 2015), may promote stress reduction and health quickly and efficiently. Nature sound booster breaks appear to be a promising area for future research with important practical implications. These findings suggest that 7- and 15-min interventions resulted in no difference in reducing facial muscle tension. These findings warrant future research. Brief nature sound mini-intervention, or what has been called a nature contact booster break (Hartig, 2006) or micro break (Bratman et al., 2015; Lee et al., 2015), may promote stress reduction and health quickly and efficiently.

6 50 Health Environments Research & Design Journal 10(1) Implications for Practice Findings consistently show that natural elements such as potted plants, a view from a window, natural sunlight are healthful design features of indoor environments. Nature sounds also appear to be a healthpromoting exposure that should be explored. In this study, brief exposure to nature sounds (ocean waves) reduced physiological and self-reported stress in participants in a workplace office or waiting room-like environment. In comparison, the participants randomized into the other listening groups (classical music or silence) did not have a significant reduction in stress. In this study, statistically significant stress reduction occurred very early in the nature sound listening group as early as 7 min of listening. This suggests that brief booster breaks or micro breaks of nature sounds may be healthful. Health promoters and design professionals may use nature sounds to help create healthy offices and or waiting rooms. Findings may also apply to other spaces as well. Declaration of Conflicting Interests The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. Funding The author(s) received no financial support for the research, authorship, and/or publication of this article. References Ahlstrom, L., Grimby-Ekman, A., Hagberg, M., & Dellve, L. (2010). The work ability index and single-item question: Associations with sick leave, symptoms, and health A prospective study of women on long-term sick leave. Scandinavian JournalofWork,Environment,&Health, 36, Annerstedt, M., Jönsson, P., Wallergård, M., Johansson, G., Karlson, B., Grahn, P.,... Währborg, P. (2013). Inducing physiological stress recovery with sounds of nature in a virtual reality forest Results from a pilot study. Physiology & Behavior, 118, Bratman, G. N., Daily, G. C., Levy, B. J., & Gross, J. J. (2015). The benefits of nature experience: Improved affect and cognition. Landscape and Urban Planning, 138, Bugbee, M. E., Wellisch, D. K., Arnott, I. M., Maxwell, J. R., Kirsch, D. L., Sayer, J. W., & Bassett, L. W. (2005). Breast core-needle biopsy: Clinical trial of relaxation technique versus medication versus no intervention for anxiety reduction. Radiology, 234, Burns, J., Labbe, E., Williams, K., & McCall, J. (1999). Perceived and physiological indicators of relation: As different as Mozart and Alice in chains. Applied Psychophysiology and Biofeedback, 24, Buss, D. M. (1995). Evolutionary psychology: A new paradigm for psychological science. Psychological Inquiry, 6, Cacioppo, J. T., Tassinary, L. G., & Bernsten, G. G. (2007). Psychophysiological science: Interdisciplinary approaches to classic questions about the mind. In J. T. Cacioppo, L. G. Tassinary, & G. G. Bernsten (Eds.), Handbook of Psychophysiology (3rd ed., pp. 1 18). Cambridge, NY: Cambridge University Press. Chafin, S., Roy, M., Gerin, W., & Christenfeld, N. (2004). Music can facilitate blood pressure recovery from stress. British Journal of Health Psychology, 9, Diette, G. B., Lechtzin, N., Haponik, E., Devrotes, A., & Rubin, H. R. (2003). Distraction therapy with nature sights and sounds reduces pain during flexible bronchoscopy: A complementary approach to routine analgesia. Chest, 123, Elo, A. L., Leppanen, A., & Jahkola, A. (2003). Validity of a single-item measure of stress symptoms. Scandinavian Journal of Work, Environment, & Health, 29, Frumkin, H. (2001). Beyond toxicity: Human health and the natural environment. American Journal of Preventative Medicine, 20, Frumkin, H. (2003). Healthy places: Exploring the evidence. American Journal of Public Health, 93, Gignon, M., Idris, H., Manaouil, C., & Ganry, O. (2012). The waiting room: Vector for health

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