Walking Green: Developing an Evidence-base for Nature Prescriptions

Study Overview
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Brief Summary
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The investigators hypothesize that walking on a nature trail will lead to greater reductions in stress and greater improvements in the capacity to direct attention as compared to walking on a suburban sidewalk. The effects of walking in these different locations will be measured using physiological and psychological outcomes. The study design is a randomized with-in person cross-over trial. Subjects will take six 50-minute walks, one walk per week for six weeks. Three walks will occur in the urban setting and three in the nature setting. The order of the conditions will be randomly assigned to each subject, so that half of the subjects will complete the urban walks first and half the subjects will complete the nature walks first. There will be a two-week washout period between the two sets of walks. Day of the week will be fixed within person, and walks will occur during the mild weather months. In the case of inclement weather, the weekly walk will be skipped and an additional week will be added to the schedule. Limiting the frequency to one walk per week maximizes feasibility of the protocol and minimizes training effects, with any training effects over time being handled primarily by randomization (condition order is balanced), but also in the statistical analysis.

Detailed Description
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Suburban walks will be mapped out in clean, safe streets with sidewalks within 3 miles of the Arboretum, in Chaska, Minnesota. A loop covering approximately 1.25 miles will be mapped. At a usual walking speed of 20 minutes per mile, a subject will complete   2 loops. Each walk will be timed so that walking speed can be included in the statistical analysis as an important covariate. Nature Walks will take place at the University of Minnesota Landscape Arboretum, which is part of the College of Food, Agricultural and Natural Resource Sciences at the University of Minnesota. The Arboretum features more than 1,215 acres of natural landscapes with over 12 miles of trails. Subjects in this study will take their nature walks on the Green Heron Pond Trail and adjacent trails that can be connected to create a walking loop of  1.25 miles, or an out-and-back course, matching the distance of the suburban walk. Heron Pond and its adjacent marsh and bog represent three naturally occurring ecosystems in Minnesota that are part of the state's geologic and landscape heritage. The bog trail passes through the most diverse ecotypes of any Arboretum hike. Oak woods, maple woods and the mosaic of intermingled wetlands along the boardwalk offer rich rewards for birders, school groups and families. The primary approach to the statistical analysis will be a repeated measures multivariable linear regression model. The outcomes will be the psychological and physiological measures of stress. The primary independent variable of interest is condition (suburban v. nature). The interaction of condition and time (week of the study) provides a formal test of intervention effects (differences between the urban and nature walks). That is, over the time course of the interventions, are there significant differences in the outcomes between the urban and nature walks? Covariates to be evaluated in the models as possible confounders include the order of the conditions (urban first v. nature first), age, gender, body mass index, and overall habitual physical activity. On an exploratory basis, the investigators will test whether these covariates also serve as modifiers of the intervention effect.

Official Title
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Walking Green: Developing an Evidence-base for Nature Prescriptions

Conditions
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Stress, Attention

Intervention / Treatment
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* Other: Suburban walk
* Other: Nature walk


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age 35 to 59 No contraindications to physical activity No major chronic diseases or specific medications that would contraindicate exercise or potentially blunt heart rate variation during exercise Exclusion Criteria: Cardiovascular disease medication Arthritis Steroids Certain blood pressure medications Diabetes Cancer Self-reported depression or anxiety / taking medication for depression or anxiety, Outside age range Inability to follow schedule including travel to arboretum Exceeding physical activity recommendations (250 minutes per week) Contraindications to walking

Ages Eligible for Study
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Minimum Age: 35 Years
Maximum Age: 59 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Other
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: Suburban<br>Study participants will wall on a suburban sidewalk setting for 50 minutes. | Other: Suburban walk<br>* Each subject is tested under the 'suburban' condition. We will compare the stress response and working memory response to walking in the two experimental conditions ((1)response to walking on a nature path and (2) response to walking on an urban sidewalk).<br>|
| Other: Nature<br>Study participants will wall on a nature path setting for 50 minutes. | Other: Nature walk<br>* Each subject is tested under the 'nature' condition. We will compare the stress response and working memory response to walking in the two experimental conditions ((1)response to walking on a nature path and (2) response to walking on an urban sidewalk).<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in Heart Rate Variability | High frequency heart rate variation using ambulatory heart rate monitors (milliseconds). | Measurements will be made at baseline one-week before the first walk, immediately before and after each walk, and within three days following the third walk of each condition (nature vs suburban). | 
| Change in Blood Pressure | Blood pressure (mmHg) using a standard blood pressure cuff. | Measurements will be made at baseline, immediately before and after each walk of each condition (nature vs suburban). | 
| Change in Cortisol Dynamics | Diurnal cortisol dynamics measured by salivary cortisol (ug/dl), as the normal drop in cortisol during the day is attenuated by exposure to chronic stress. | Measurements will be made before each walk of each condition (nature vs suburban). | 
| Change in Cytokine Blood Concentration | Pro- and anti-inflammatory cytokine concentrations in blood (pg/mL), as stress typically induces an inflammatory response. Blood samples are collected by pricking the subject's finger-tip, collecting drops of blood on Protein SaverTMpaper (Whatman) and then drying the blood spots. The dried blood spots (DBS) are frozen and stored until assayed. | Measurements will be made before each walk of each condition (nature vs suburban). | 
| Change in Attention restoration | The Backward Digit Span test is one of the oldest tests used to evaluate working memory and is used to assess capacity to direct attention (i.e., attention restoration). | Measurements will be made at baseline one-week before the first walk, immediately before and after each walk, and within three days following the third walk of each condition (nature vs suburban). | 
| Change in CESD | CESD: Stress is strongly associated with depression. To measure depressive symptoms we will use the Center for Epidemiological Studies Depression Scale (CESD). Scores are determined by summing the participants' answers to all 20 items from 1 (less than 1 day) to 4 (5-7 days) pre- and post-walk in each intervention location (nature vs suburban). | Measurements will be made at baseline, immediately before and after each walk of each condition (nature vs suburban). | 
| Change in PANAS | PANAS: Stress is associated with decreased positive and increased negative affect (mood). We will measure affect using the Positive and Negative Affect Scale (PANAS). Scores are determined by summing the participants' answers to all 20 items from 1 (very slightly or not at all) to 5 (extremely) pre- and post-walk in each intervention location (nature vs suburban). | Measurements will be made at baseline, immediately before and after each walk of each condition (nature vs suburban). | 
| Change in STAI | Anxiety: Stress is associated with increased levels of anxiety. Anxiety will be measured using the State and Trait Anxiety Inventories (STAI). Scores are determined by summing the participants' answers to all 20 items from 1 (not at all) to 4 (frequently so) pre- and post-walk in each intervention location (nature vs suburban). | Measurements will be made at baseline, immediately before and after each walk of each condition (nature vs suburban). | 
| Change in Perceived stress | Perceived stress: Cohen's perceived stress scale (PSS) will be used to measure the extent to which subjects assess the events and situations in their lives to be stressful. Scores are determined by summing the participants' answers to all 10 items from 1 (never) to 4 (very often) pre- and post-walk in each intervention location (nature vs suburban). | Measurements will be made at baseline, immediately before and after each walk of each condition (nature vs suburban). |