Gladwell et al. Extreme Physiology & Medicine 2013, 2:3
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REVIEW

Open Access

The great outdoors: how a green exercise
environment can benefit all
Valerie F Gladwell*, Daniel K Brown, Carly Wood, Gavin R Sandercock and Jo L Barton
Abstract
The studies of human and environment interactions usually consider the extremes of environment on individuals or
how humans affect the environment. It is well known that physical activity improves both physiological andpsychological well-being, but further evidence is required to ascertain how different environments influence andshape health. This review considers the declining levels of physical activity, particularly in the Western world, andhow the environment may help motivate and facilitate physical activity. It also addresses the additional
physiological and mental health benefits that appear to occur when exercise is performed in an outdoor
environment. However, people’s connectedness to nature appears to be changing and this has important
implications as to how humans are now interacting with nature. Barriers exist, and it is important that these areconsidered when discussing how to make exercise in the outdoors accessible and beneficial for all. The synergistic
combination of exercise and exposure to nature and thus the ‘great outdoors’ could be used as a powerful tool tohelp fight the growing incidence of both physical inactivity and non-communicable disease.
Keywords: Green exercise, Physiology, Natural environment, Physical activity, Motivation, Health

Review
Background

Most discussions of human interactions with the environment concern the potential challenges they place on
one another. These usually concern the extreme environmental demands such as those seen at high altitude,
at depth or in extremes of temperature. Alternatively,
they express the growing human population’s ongoingtendency to negatively influence the delicate balance of
nature, which developed for millions of years prior to
our evolutionary invasion.
With the multiplicity of the ‘great outdoors’ including
forests, seaside, countryside, parks, local green areas andeven gardens, another conversation considers the role ofenvironment in benefiting human health. Green or natural spaces have been considered to be advantageousfor health for many years. For example, in the UK during
the 19th century Industrial Revolution, wealthy philanthropists developed urban parks for the benefit of the
public’s health, and hospital gardens were considered an
important addition for their believed healing properties[1,2]. A study in the early 21st century has further* Correspondence: vglad@essex.ac.uk
School of Biological Sciences, University of Essex, Colchester CO4 3SQ, UK

supported this belief, demonstrating an association between improved health outcomes and amount of surrounding ‘green space’ [3,4]. Subsequently, how and why
the great outdoors may elicit health benefits has become
a focal point for research.
Our hunter-gatherer ancestors existed with the outdoor
natural environment for thousands of years, and it ishypothesised that this provides present day humans withan innate affiliation with nature [5]. In addition, natureprovides an environment that does not require our direct
attention, giving nature restorative properties therefore
allowing recovery from mental fatigue [6] and attention
restoration [7]. Although in the Western world, lesspeople are involved in the natural environment on a daily
basis, in particular reduced numbers working on the land,
many people seek out nature and undertake outdoor recreational activities. Currently, there is an increasing trend
for people to undertake outdoor endurance challenges
but, paradoxically, there is a greater proportion of the
population with insufficient physical activity levels to meetcurrent health guidelines [8]. Recent reviews indicate thatexercising outdoors appears to be more beneficial to mental health over indoor activities [9] and furthermore, natural environments have a greater impact on psychological© 2013 Gladwell et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, andreproduction in any medium, provided the original work is properly cited.

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health especially when exercise is incorporated [10]. To
describe this potential synergistic benefit to health that
occurs when exercising whilst being exposed to nature,
the term ‘green exercise’ was adopted in 2003 [11] andpublished through peer-review in 2005 [12].
Pretty et al. [11] demonstrated that green exercise can
improve mental well-being and markers of physiologicalhealth. There is subsequent preliminary evidence at
physiological [13-15], psychological [9,16,17], biochemical [18] and social levels [17], which suggests that green
exercise might have a useful role in primary and secondary prevention of disease. Moreover, there is evidence tosuggest a role for green exercise in rehabilitation programmes [17]. In addition, engaging sedentary individuals in green exercise could be an effective vehicle indriving behavioural change by improving adherence
rates to exercise programmes [19]. There is still a needto investigate the mechanisms behind observed healthbenefits of the natural environment [9,10]. A greater
understanding of how nature positively interacts withhuman socio-biology may be mutually beneficial to both
health and the environment.
The focus of this paper is to identify literature regarding physiological changes which occur as a product ofparticipating in green exercise. Additionally, the likelyinteraction between these physiological changes and thewell-documented psychological alterations will be discussed with regard to their potential health benefits. Furthermore, the impact that the great outdoors may have on
exercise adherence and motivation to exercise will be
explored in the context of increasing physical activity
levels. Therefore the aims of the review are the following:
1. Outline the declining physical activity levels in theWestern world and how the ‘green’ environment may
help to decrease perception of effort and improve
motivation to increase physical activity levels
2. Discuss the impact of green exercise on physiologicaland psychological markers of health and whether
these impacts are enhanced by the green
environment
3. Explore the mechanisms that are attributed to green
exercise for improvements to health and
4. Discuss the consequences of the disengagement withnature and its impact on health.
Declining physical activity levels

Worldwide, 31.1% of adults are physically inactive [20].
Some of the decline is attributed to technologicaladvances through the agricultural and industrial revolutions, and more recently, digital revolution. The focus ofmuch structured physical activity in the developed world
has also shifted indoors to gymnasia, sports halls, and towithin the home; proportionally less physical activity is

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undertaken outdoors. Due to rapid urbanisation andnearly half of the world’s population living in urban
areas [21], less green space and quality green space isavailable in which undertake physical activity or sport.
Green spaces, physical activity and health

The decline in physical activity is resulting in hugeincreases in physical disability and disease [22] and a rising number of cases of mental ill-health [23]. It is essential, therefore, to find ways of engaging all individuals
to improve health and prevent further increases in noncommunicable diseases. The use of outdoor naturalenvironments for physical activity and health is not new.
For 99% of human history, not only we have lived off theland and sought nature for basic survival needs andhealth, but also for pleasure and physical activity. Morerecently climbers, hill-walkers, mountain bikers and endurance athletes have all enjoyed the great outdoors andgreen spaces. It may not only facilitate enjoyment forparticipants and improve adherence [19], but may also
encourage positive physical activity behaviours which are
likely to produce greater health gains. As we maybe still
genetically designed to be hunter-gatherers in the great
outdoors, we are not being stimulated physically or mentally in the same way and this may be detrimental tohealth. One hypothesis suggests that we are all born with
an emotional affiliation for other living organisms, i.e.
nature loving [5], which may mean as part of our genetic
makeup we are innately predisposed to desire nature
contact, and thus maybe green exercise should be used
to facilitate physical activity to improve health.
Green exercise, perception of effort, motivation andbehaviour change

Although green exercise is perceived to boost health andthis can be used as a powerful extrinsic motivation forexercise, not everyone will be motivated by this. People
are motivated to exercise for many different reasons[24]. Some are extrinsically driven by external factors including what others may think of them, whilst others are
intrinsically driven, maybe due to the enjoyment or theexcitement of the challenge. Others engage for healthbenefits, whereas some may take part for the social aspect. The promotion of the social and entertainment
benefits of physical activity appear to be more successful
than those promoting health benefits to persuade individuals to partake in physical activity [25]. Green exercise
may help motivation to undertake physical activity by increasing enjoyment and escapism from everyday life,
with both a social and entertainment value.
There is even some evidence to suggest that exercise
may feel easier when performed in the natural environment. When allowed to self-select walking speed, participants tend actually to walk faster outdoors, compared toGladwell et al. Extreme Physiology & Medicine 2013, 2:3
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indoors. Paradoxically, they report a lower rating of perceived exertion [26].
When asked to reproduce a given level of perceived
exertion indoors and outdoors, individuals tend to walkfaster at a greater physiological effort (verified by heart
rate and blood lactate), suggesting they perceive exercise
to be less demanding when performed in the natural environment [27]. A recent paper by members of our research group [28] explored the impact of colour in avideo which simulated cycling within a natural environment. Participants cycled for 5 min in three different
conditions: an unedited video (predominantly showing
green foliage), the same video but with a red filter, andthe same video with no colour. Interestingly, despite thevideo images all being the same apart from the colour,
the rate of perceived exertion was decreased in the normal
image compared to the other two conditions. Furthermore, total positive mood was increased (as mentioned
later in the green exercise and health section). This potentially provides support for the first time that ‘greenness’ is an important component of alterations that are
seen. There were no differences in physiological markers, e.g. heart rate and oxygen consumption.
Perception of effort is highly complex, comprisingmultiple components [29]. Perception of effort during
exercise comprises input from the brain and integrationof information from the feed-forward centre. The latter,particularly, may be influenced by mood and anxiety.
There is also feedback from the various different sensors
within the body, including central receptors, e.g. baroreceptors, chemoreceptors, and those within the muscles,
e.g. metaboreceptors and mechanoreceptors. These provide physiological and biomechanical information. Input
also arises from auditory and visual information. In
addition, there will also be the input of cognitive factors
like prior experience at a given effort and context of theexercise, e.g. is it training or competition? All of these
are integrated pre-consciously and will determine what a
participant perceives the effort of exercise to be.
In the case of green exercise, the inputs from the visual system, the feed-forward centre as well as cognitive
input may be able to act as a distractive stimulus, reducing the perception of exertion. Indeed this has beensuggested for other distractive stimuli e.g. music [30]. It
is likely that promoting attention to an external pleasantand green environment reduces awareness of physiologic
sensations and negative emotions, thus minimizing theperception of effort. As discussed, mood is enhanced
and perception of effort appears to be reduced withgreenness [28]. Further evidence is shown, with real andsimulated nature, in comparison to other environments(built or indoor) the increasing cognitive components
including mood [9,10,12,16,31]. This suggests that green
exercise reduces perceived effort and allows individuals

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to work at higher workloads, which may help to increase
the amount of physical activity undertaken and motivation to continue. However, there is a dearth of studies
that have investigated whether physical activity levels(duration and frequency) are altered by the exercise
environment.
The restorative properties of an environment appear
to mediate the frequency of physical activity [19], but
most studies focus simply on the relationship between
percentage of green space (usually surrounding housing)and physical activity levels. While one European study
reported that individuals living in a greener environment
were three times more likely to be physically active witha 40% lower chance of being overweight or obese [32],other authors have reported no association between thequantity of immediate green space and self-reported
levels of physical activity [33,34]. The limitation of the
majority of studies is the paucity of information regarding participants’ actual use of local green space, the perceived quality or even access to green space. Access togreen space has been shown to be important for mental
health and is associated with longevity and decreased
risk of mental illness in Japan [35], Scandinavia [36] andthe Netherlands [37]. Access also improves perceptionof general health [38,39] and quality of life in ageing
populations [40]. The quality of the green space may
also be associated with health as the biodiversity (i.e.
range of species of plants and animals that are present
in the environment) enhances the psychological healthbenefits [41].
It appears that having access to green spaces may facilitate physical activity and thus drive behaviour change
by decreasing perception of effort and increasing motivation. An increase in physical activity levels will have a
direct impact on health parameters. However, would
green exercise offer greater benefits in terms of othermarkers of health than urban or indoor exercise?
Green exercise and health

A systematic review of studies comparing indoor versus
outdoor activity conducted in natural environment suggests that outdoor activity which is conducted in a natural or green environment causes greater feelings ofrevitalisation and positive engagement [9]. All types ofgreen exercise activities also improve self-esteem andnegative mood subscales, such as tension, anger and depression [42,43]. Interestingly, the first five minutes ofgreen exercise appears to have the biggest impact onmood and self-esteem, suggesting an immediate psychological health benefit [16]. Participating in green exercise
activities also affects physiological parameters which differ
to the changes observed in matched activity in an urban environment [13]. There are, however, only a handful of studies that have been conducted to investigate physiologicalGladwell et al. Extreme Physiology & Medicine 2013, 2:3
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health markers [13,14,18,44,45]. Physiological outcomes
have included heart rate, blood pressure and autonomic
control (using heart rate variability) and endocrine markers
including noradrenaline, adrenaline and cortisol (an objective measure of stress).
Post-exercise blood pressure returns to baseline values
more quickly after exercising in front of rural scenes
compared to urban settings [12]. Japanese studies monitoring the physiological effect of walking within real forest
environments (Shinrin-Yoku or forest bathing) reported
similar findings. Significantly lower systolic and diastolicblood pressure occurred following both viewing alone
and walking in the forest environment when comparedto the same activity in an urban environment distinctly
lacking in any vegetation or plantation [13,46,47]. A reduction in sympathetic activation assessed by lowered
urinary noradrenaline may have elicited these effects on
blood pressure [46]. Early work by Ulrich [48] suggested
exposure to nature-heightened arousal and attention
capacity with observed increases in heart rate. However,viewing scenes of nature following exposure to a stressful video [49] later confirmed that increases in parasympathetic activity occur more synonymous with loweredheart rate. In addition, heart rate variability (HRV), an
indicator of autonomic function, increased following
both viewing and walking in a forest environment [50].
High HRV suggests healthy autonomic nervous system
function and is inversely correlated with cardiovasculardisease risk. HRV gives an indication of the adaptabilityof the nervous system in responding to challenges
experienced by an individual such as stress and exercise. Using HRV analysis, a study from Japan [47]showed a tendency for a higher HRV, reflective of parasympathetic activity, whilst participants sat outside
within a forest environment. This effect has been
repeated indoors in a controlled environment enablingviewing nature alone to be highlighted as a cause forincreased parasympathetic activity [14] and decreased
heart rate [45].
Increasing the level of psychological stress is detrimental to health, and with stress reportedly increasing [51],methods to help to cope with stress are required. Nature
may be one such solution as it does also appear to reduce stress markers. Endocrine markers adrenaline, noradrenaline and the stress hormone cortisol, all fall after
being within nature, suggesting that exposure to nature
affects the two main stress systems, the sympathoadrenal medullary and the hypothalamus-pituitaryadrenal axis [13,52]. These studies suggest that exposure
to forest environments is relaxing and has stressreducing properties as observed by reductions in thephysiological parameters of blood pressure, heart rate(accompanied by an increase in HRV) and endocrine
markers. A further effect associated with the reduction

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in adrenaline is the improved immune function in theform of increased natural killer cell activity. Naturalkiller cell activity increased for up to 30 days after athree-day trip to a forest for males but only seven days
for females [52]. This suggests that the interaction withnature does not have to be extreme to gain wide-ranging
physiological health benefits.
Connectedness to nature

Parental physical activity behaviours influence not only
children’s physical activity patterns but also their attitudes to physical activity and choice of exercise environment. If children engage less with nature, when they
become parents their offspring may also be less likely toseek out nature. A cycle of unfamiliarity and disconnectedness is then likely to be passed from generation to
generation. The human costs of this separation include
attention difficulties and behavioural problems, higher
rates of emotional and physical illness and diminisheduse of the senses [53,54].
Despite evidence suggesting that natural environments
facilitate physical activity and provide health benefits[10], relatedness and/or connectedness to nature is declining in particular areas and parts of the world, especially in children and adolescents. This is primarily due
to a lack of contact with nature, termed ‘the extinctionof experience’ [55] or ‘nature deficit disorder’ [53]. The
current generation of youth is largely restricted fromaccessing nature due to parental fears regarding strangers, traffic and criminal activity [56-58]. Only 10% of
today’s generation of youth has regular access to nature,compared to the 40% of adults who did so when they
were young [59]. Adolescents living in urbanised areas
often perceive the countryside to be intimidating and are
reluctant to visit if they have not experienced it as children. The amount of time spent outdoors does appear
to be a positive correlate of physical activity in both children and adolescents [60-62]. Although small amountsof time are spent in green space in children, those who
do tend to undertake higher intensity activity [63]. However, if generations become disengaged with nature andless importance is placed on the environment as a useful
resource for health, the distance to travel to get to thegreen spaces will increase.

Discussion
The purpose of this review was to identify and discuss
how the great outdoors can benefit the general population. With declining physical activity levels in the developed world, initiatives to curb this downward trend areincreasingly important. The great outdoors has been a
crucial part of human evolution, and it is likely that thisreaches into modern beliefs and attitudes towards nature, both conscious and unconscious [5]. There isGladwell et al. Extreme Physiology & Medicine 2013, 2:3
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evidence to suggest that participating in physical activity
in a natural environment, or green exercise, might engage people in physical activity by increasing enjoymentof participation, offering social interaction and increased
frequency of activity [19]. Interestingly, participating ingreen exercise activities alters the perception of effort.
For those people engaging in green exercise, the natureelement may help achieve a greater intensity of exercise
without perception of effort changing. If a person perceives exercise to be easier, it has the potential to be
more enjoyable. By reducing the perceived effort experienced during green exercise, a greater intensity may beachieved during the exercise whilst also maintaining adherence to and motivation for the activity. Taken all together, this should help to improve physical activity
behaviour. Future studies need to explore the impact of
the environment on perception of effort in greater
depth, incorporating input from other senses. Furthermore, it needs to examine to what intensity of exercise
nature may act as a distracter to perception of effort.
It has been the purpose of previous reviews to assess
the role of nature from a health and well-being perspective. There is evidence linking the presence of surrounding green spaces to better physical and mental health.
This evidence suggests that better health is impacted by
the quality of green space, in particular, by levels of biodiversity. Further research should investigate the importance of biodiversity on health for the careful managementof these areas to ensure the maximum benefit for healthand for the environment. Considering both the quality of,and access to, green space, evidence for the impact on
physical activity is conflicting. Many studies have notexplored the use of more distant outdoor spaces for recreational use. The majority of studies use self-reported
details of physical activity type, duration and intensity,
which is subject to bias. Future studies should therefore
use objective methods for assessing both physical activity
and exercise environment. Accelerometry and Global
Positioning System monitoring including Smartphones
should enable this [63].
Engaging in physical activity outdoors provides opportunities linked to better health which is unavailable fromindoor activity, such as exposure to sunlight for sufficient vitamin D levels. Additionally, outdoor activity
shows greater improvements in mental health compared
to indoor activity [9]. Building on the health benefits ofoutdoor activity, including exposure to nature during
outdoor activity, has a synergistic impact on markers ofmental well-being and physiological markers [10]. The
study to date has identified changes in cardiovascular,
endocrine and autonomic function which suggests a psychophysiological impact of nature and green exercise.
However, little has been done to identify the mechanisms
by which these changes are influenced by experiencing

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nature. Although seemingly counterintuitive for the purpose of research concerning the great outdoors, the use ofcontrolled indoor environments is important for exploring the alteration of physiological parameters alreadyobserved. This will have important implications for using
outdoor exercise for rehabilitation or prevention of disease, especially cardiovascular disease.
There are however, disadvantages and barriers to using
the great outdoors. How the outdoor space is perceived
influences usage. Although individual preferences differ,safety and opportunity for socialization are shown to be
the key determinants for use of green spaces [64]. Ease ofaccess, including transportation to the place of interest,
suitable links between areas (i.e. footpaths not continuing
without crossing/walking down busy roads/private land)
all affect participation. Furthermore, socioeconomic status
also alters local green space usage for physical activity.
Higher socioeconomic status enhances park safety, maintenance, attractiveness and opportunity for socializationand is an important determinant of access to more remotenature (i.e. due to transport required to reach destination).
Concerns for personal safety will motivate people to avoid
perceived dangerous situations, and going outdoors insome areas does pose a threat. This is influencing parental
choices, and there is a growing disconnection with outdoor activity and more specifically nature in the new generation of children. Also, neighbourhood crime safety,
aesthetics, and traffic safety all influence participationlevels. Safety concerns are also accentuated if the area isremote, where injuries or exposure to the outdoors for a
prolonged period of time, especially in extremes of weather may occur. This is predominantly an issue for thoseindividuals who are unprepared, not trained or not supervised correctly.

Conclusions
To summarise, outdoor natural environments may provide some of the best all-round health benefits by increasing physical activity levels with lower levels ofperceived exertion, altering physiological functioning including stress reduction, restoring mental fatigue, andimproving mood and self-esteem and perceived health.
Thus, exercise within green spaces and the great outdoors may be a useful natural medicine (vis medicatrix
naturae) [65] to address health challenges facing developed countries. Alongside the social aspect which someindividuals crave, it may also increase enjoyment and adherence to bring about positive behaviour changes in alarge proportion of the population.
The great outdoors, therefore, should not be just considered a playground for those who seek the thrills of extreme sports, but emphasis should be placed on accessfor all. One way of doing this is to ensure urban parks
are maintained and are developed to produce interestingGladwell et al. Extreme Physiology & Medicine 2013, 2:3
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areas of high biodiversity, as well as more open playareas, where more sports may be played, increasing opportunities for exercise. Not only may both types of areaelicit greater health benefits, but also may offer protection for the natural environment and preserve species.
The management of countryside, forests and more extreme environments also needs careful consideration including ensuring access for all, but without the pressureof too many people visiting these areas, as this would
potentially destroy the natural environment that elicits
these health benefits. The challenge for researchers inthis field is not only determining whether knowledge ofnature’s health benefits can act as a motivator for behaviour change, but also ensuring that the increased use of‘nature as a therapy’ is accompanied by a conservationist
approach to ensure preservation of the environment. It
is hoped that by more individuals partaking in green exercise and enjoying the great outdoors, they will retain
their evolutionary connection with nature and act to become more protective of it.
Abbreviation
HRV: Heart rate variability.
Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
All authors helped plan, develop and write the manuscript. All authors readand approved the final manuscript.
Received: 29 July 2012 Accepted: 2 November 2012
Published: 3 January 2013
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