Routine physical activity (PA) is imperative to maintain or improve long-term physical and mental health, and there is emerging evidence that PA in outdoor environments can further enhance these benefits. However, lifestyle trends demonstrate a decrease in PA and in time spent outdoors for all Americans (1,2). Although traditional exercise prescriptions indicate frequency, intensity, duration, and time, there has been no emphasis on place, or where to exercise within an exercise prescription. However, this is slowly changing, as seen with projects such as the “nature pyramid” (3), indicating that doses of nature are vital to overall health.
Because of the emerging evidence of outdoor exercise benefits, communities are beginning to dedicate resources to outdoor PA spaces. These spaces are being designed to be accessible to people of all ages and abilities to promote active and healthy lifestyles, all while being in the outdoors.
AMERICAN TIME USE AND OUTDOOR RECREATION TRENDS
More and more, Americans are choosing to spend time in front of a screen. On average, Americans ages 15 and older spend more than 3 hours a day watching TV, playing video games, and/or using their computers for leisure, in addition to time spent on computers for work/school or time spent on smart phones. Conversely, this same population is spending less than 30 minutes a day participating in sports, exercise, or physically active recreation (4).
Despite the overall decline in PA, outdoor activities are actually rising in popularity. In fact, annual participation in outdoor recreation has increased steadily over the past decade, with nearly half of Americans (48.6%) engaging in some form of outdoor activity. Outdoor recreation provides an inspiring method of exercise, thereby increasing the amount of daily PA and enhancing long-term motivation (5). Combining the natural setting with novel activities increases stimulation and the fun factor of exercise, with the most popular activities being those that require little specialized equipment, such as hiking or trail running. Other activities with a low skill threshold attract participants who may be averse to traditional modes of exercise. Paddle boarding, for example, has increased in participation by 18% over the last 3 years alone. In a study of 24,134 Americans, aspirational participants, those who have yet to participate in an activity, regardless of age, were drawn to outdoor recreation over sports and traditional leisure activities (6).
Despite the overall decline in PA, outdoor activities are actually rising in popularity. In fact, annual participation in outdoor recreation has increased steadily over the past decade, with nearly half of Americans (48.6%) engaging in some form of outdoor activity.
BARRIERS AND CONSTRAINTS
Myriad reasons exist for a lack of routine PA (7,8), both external (e.g., lack of time) and internal (e.g., lack of motivation). Although outdoor activities may remedy some of the common deterrents to exercise, it may complicate others. Outdoor environments increase motivation to exercise, evidenced by perceived enjoyment and increased persistence of those who exercise outside (9,10). Certain external constraints, such as social judgments and cost of membership, also are reduced in public park environments (5). However, weather conditions, safety concerns, lack of information, and lack of specialized skills can prevent participation in certain outdoor activities or at certain times of the year (6). The barriers to outdoor exercise are compounded for minorities and marginalized populations, who cite lack of easy access, safety concerns, and poorly maintained facilities as common constraints (11). Given that many barriers to outdoor activities are external (e.g., information, access, safety), they can often be addressed through policy and program design. Therefore, it may be more feasible to enable citizens to participate in something they would enjoy doing (e.g., walk through a park) than to convince them of the necessity of routine exercise.
PHYSICAL AND MENTAL HEALTH BENEFITS ASSOCIATED WITH OUTDOOR EXERCISE
PA in any environment has been shown to tremendously benefit human health. The benefits of routine exercise include reduced risk of cardiovascular disease, type 2 diabetes, obesity, and some cancers. In addition, those who participate in regular PA have increased muscle and skeletal strength, improved mental health and mood, and increased longevity (12). Exercising outdoors, or green exercise, can influence the frequency, duration, and intensity of workouts. Local parks and trails can increase PA in adjacent neighborhoods by up to 25%, and park users make fewer trips to the doctor for chronic illness (13). In fitness centers, some participants (especially neophytes) often feel uncomfortable due to real or perceived judgments by others (14). In natural settings, individuals are exposed to sensory experiences that induce a mindset of belonging and even a sense of awe (5). Green exercise also can influence the level of perceived exertion because natural scenery enhances positive attitudes and emotions, similar to exercising while listening to music (5).
Exercising outdoors can induce a host of significantly higher positive outcomes as compared with indoor settings, including improved vitality, mood, and self-esteem; reduced stress and mental fatigue; and lower rates of anger and depression (14).
Exercising outdoors can induce a host of significantly higher positive outcomes as compared with indoor settings, including improved vitality, mood, and self-esteem; reduced stress and mental fatigue; and lower rates of anger and depression (14). In clinical settings, children diagnosed with ADHD demonstrate a greater reduction of attention deficit symptoms after engaging in activities in natural green spaces (15). In fact, as little as 20 minutes outdoors produces an effect equivalent to a standard dose of Adderall (16).
Even participating in low-intensity activities in natural environments can lower blood pressure and heart rate, enhance levels of vitamin D, reduce rates of myopia, and promote general happiness (5,17,18). Given the host of benefits associated with time spent outdoors, researchers have begun to recommend a minimum dose of outdoor time for optimal health. Similar to the U.S. Centers for Disease Control and Prevention–recommended dose of 150 minutes of PA per week, the Finnish Forest Research Institute recommends 5 hours of time in a forest every month. (19)
Although preventive medicine has received some attention and legitimacy through past health care legislation, its focus within the health care industry is rapidly accelerating. Prevention is certainly more cost-effective for insurance providers, and many chronic illnesses can often be effectively managed through lifestyle changes. Nearly three in five American adults take one or more prescription medications, led by antidepressants and treatments for high cholesterol and diabetes (20). The Exercise is Medicine® initiative (EIM) has championed the fight for healthy lifestyles over medication with measured success. Outdoor prescriptions are an extension of the EIM model, albeit less standardized. Similar to EIM, clients may be referred to program providers based on their current health condition, and in some cases may receive discounted insurance rates, free or reduced memberships, or other incentives to participate in outdoor exercise.
Still in its infancy, the outdoor exercise prescription movement currently consists of loosely connected initiatives managed by local, state, and federal parks systems; municipal governments; health care systems; and/or program providers. Some, such as the Boston-based OutdoorsRx (www.outdoors.org) exclusively refer clients to a single program provider, whereas others (www.parkrxamerica.org) provide information to connect clients with local outdoor resources in their area. Still others have built a model based on a single park or greenway resource that is sponsored by the local health care community (https://greenvillerec.com/ghs-swamp-rabbit-trail/). With a heavy reliance on geographical setting, activities vary by location and can include scavenger hunts in neighborhood parks, biking on urban greenways, hiking on regional trails, and extensive trips in state and national forests.
Lacking uniformity in activities, program accreditation, and standardized prescription protocols, the movement is still finding its identity. However, sample program models and protocols are available from established initiatives. The San Francisco Bay area park system, for example, provides a complete “ParkRx Toolkit” that walks you through the process to engage clinical and community-based partners, public health administrators, and parks and urban designers (http://www.hphpbayarea.org/). Despite the lack of a universal programmodel, dedicated health professionals can find a way to implement outdoor prescriptions in their area based on their unique resources; health care providers, programmers, and park facilities.
Despite the lack of a universal program model, dedicated health professionals can find a way to implement outdoor prescriptions in their area based on their unique resources; health care providers, programmers, and park facilities.
Regular PA is a vital component of a healthy lifestyle, and time spent outdoors provides additional mental and physical health benefits. The EIM movement has laid a solid foundation for bringing together researchers, health care providers, community programmers, and public health professionals to address negative health trends. Expanding that model to incorporate open spaces will unite the public health and outdoor industries, while also enhancing parks and public spaces, in an effort to increase quality of life for all citizens. Despite challenges due to the lack of program uniformity, outdoor prescriptions can be a powerful tool for public health professionals. Clients that demonstrate a lack of motivation for fitness training may respond positively to paddle boarding instruction, a family biking excursion, or a relaxing walk through their local park. This may not only enhance participation and enjoyment, but positions public health professionals as connectors to local assets rather than our physiological conscience.
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