The Effect of Physical Activity Interventions Carried Out in Outdoor Natural Blue and Green Spaces on Health Outcomes: A Systematic Review

Abstract

In the last few years, interest about the natural environment and its influences on health conditions has been growing. In particular, physical activity interventions carried out in blue and green environment are being investigated as a potential strategy to increase health outcomes in people with and without chronic conditions. Many recent studies reported positive results, but a high number of these studies were focused on people with mental or physical disorders. In this scenario, the present systematic review, conducted according to the PRISMA statement, was aimed at investigating the existing evidence regarding the effects of physical activity interventions carried out in green–blue space settings involving healthy people. A literature search was performed through PubMed, Cochrane, Cinahl, and Psychinfo, and the quality of each study was assessed. Out of 239 identified articles, 75 full texts were screened. Six eligible studies showed an improvement in health outcomes, such as well-being, mood, and physical performance, in the experimental group compared with the control group. No exhaustive conclusion can be drawn based on available evidence. However, this systematic review highlighted the need to extend this kind of intervention to reveal more robust evidence that green and blue exercises benefit health.

Full text

Citation: Marini, S.; Mauro, M.;
Grigoletto, A.; Toselli, S.;
Maietta Latessa, P. The Effect of
Physical Activity Interventions
Carried Out in Outdoor Natural Blue
and Green Spaces on Health
Outcomes: A Systematic Review. Int.
J. Environ. Res. Public Health 2022,19,
12482. https://doi.org/10.3390/
ijerph191912482
Academic Editors: Mirja Hirvensalo
and Paul B. Tchounwou
Received: 18 August 2022
Accepted: 27 September 2022
Published: 30 September 2022
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4.0/).
International Journal of
Environmental Research
and Public Health
Review
The Effect of Physical Activity Interventions Carried Out in
Outdoor Natural Blue and Green Spaces on Health Outcomes:
A Systematic Review
Sofia Marini 1, Mario Mauro 1, Alessia Grigoletto 2, * , Stefania Toselli 2,†
and Pasqualino Maietta Latessa 1, †
1Department for Life Quality Studies, University of Bologna, 47921 Rimini, Italy
2Department of Biomedical and Neuromotor Sciences, University of Bologna, 40126 Bologna, Italy
*Correspondence: alessia.grigoletto2@unibo.it
† These authors contributed equally to this work.
Abstract:
In the last few years, interest about the natural environment and its influences on health
conditions has been growing. In particular, physical activity interventions carried out in blue and
green environment are being investigated as a potential strategy to increase health outcomes in
people with and without chronic conditions. Many recent studies reported positive results, but a
high number of these studies were focused on people with mental or physical disorders. In this
scenario, the present systematic review, conducted according to the PRISMA statement, was aimed at
investigating the existing evidence regarding the effects of physical activity interventions carried out
in green–blue space settings involving healthy people. A literature search was performed through
PubMed, Cochrane, Cinahl, and Psychinfo, and the quality of each study was assessed. Out of
239 identified articles, 75 full texts were screened. Six eligible studies showed an improvement in
health outcomes, such as well-being, mood, and physical performance, in the experimental group
compared with the control group. No exhaustive conclusion can be drawn based on available
evidence. However, this systematic review highlighted the need to extend this kind of intervention to
reveal more robust evidence that green and blue exercises benefit health.
Keywords:
blue exercise; green exercise; healthy adults; blue–green space setting; natural outdoor
environment; physical activity intervention; outdoor exercise; health promotion
1. Introduction
Green spaces can be defined as open areas of ground, covered by vegetation, which
includes parks and gardens [
1
]. On the other hand, blue spaces are accessible settings
principally consisting of water such as rivers and lakes [2]. In recent years, there has been
an increase in the literature about these kinds of natural environments: green and blue
spaces [
1
]. This is linked to the worldwide growing urbanization [
3
]. One of the major
challenges for the future will be to create cities on a human scale that can be habitable
ensuring wholesome conditions, and to achieve this will be fundamental to safeguarding
natural environments. Recent systematic reviews suggest that people, especially those
with mental or physical disorder, can obtain health benefits if they use and are exposed to
natural outdoor environments [
4
,
5
]. Therefore, access to green and blue spaces, such as
beaches and gardens, provides opportunities to support and promote public health and
well-being [6,7].
There are an increasing number of studies with the aim of estimating the impact
of access and exposure to neighborhood green and blue spaces on the risk of mental
health conditions and the opportunity for promoting well-being [
8
,
9
]. Up-to-date research
indicates that the benefits may be different due to the population groups, context, and
health outcome [
10
,
11
]. Moreover, the mechanisms that justify the connection between
Int. J. Environ. Res. Public Health 2022,19, 12482. https://doi.org/10.3390/ijerph191912482 https://www.mdpi.com/journal/ijerph

Int. J. Environ. Res. Public Health 2022,19, 12482 2 of 15
the natural environment and well-being are still unclear [
12
,
13
]. Even if some studies
proposed different mechanisms to explain this relationship, one of these mechanisms is the
opportunity to perform physical activity (PA) [
14
–
16
]. Adequate PA levels are essential,
given that PA is a fundamental aspect of human health [
17
]. Indeed, conducting an active
lifestyle contributes to the prevention of noncommunicable diseases such as stroke, diabetes,
hypertension, overweight, and obesity. Moreover, it improves the well-being, mental health,
and quality of life [
17
]. Despite this evidence, a great part of the population is still inactive.
The use of green and blue spaces can help people to achieve the right amount of PA. Indeed,
it can facilitate PA, social interaction, and contact with nature, providing multiple health
benefits [
8
,
18
–
22
]. Experimental studies suggested that outdoor exercise can be a possible
alternative to indoor exercise and that exposure to a natural environment is connected
to a higher amount of PA and a lower mortality rate [
23
–
25
]. In addition, it seems that
performing PA in a natural environment can have supplementary benefits in comparison
with PA performed in an indoor environment [26].
Therefore, evidence of such health benefits might be of high relevance for healthcare
professionals, urban planners, and policymakers, who can help translate available evidence
into interventions and policies targeted to improve health. However, the knowledge base
is limited to the green and blue spaces evaluation of exposures or nearness separately
considering green or blue or involving a nonhealthy population. In such a scenario, the
aim of the present systematic review was to investigate the existing evidence regarding the
effects of PA interventions performed in a natural environment involving healthy people
(aged ≥18 years).
2. Materials and Methods
2.1. Data Sources and Search Strategy
The present systematic review was prepared in accordance with PRISMA recommen-
dations and guidelines [
27
]. The protocol was registered in the International Prospective
Register of Systematic Reviews (PROSPERO).
Table 1summarizes the Patients, Interventions, Comparators, Outcomes, Time, and
Setting (PICOTS) criteria drafted to address the primary search aim.
Table 1. PICOTS criteria for eligibility.
Parameter Inclusion Criteria Exclusion Criteria
Population Healthy people
Age range: adult (aged ≥18 years)
People with acute or chronic conditions
People aged under 18
Intervention
Outdoor PA intervention is carried out in the natural
environment and natural and mixed settings (specifically
green and blue spaces)
Absence of PA intervention;
indoor PA intervention
Comparator
Standard treatment
No PA intervention
Another type of PA intervention
Outcome
Physical fitness
Quality of life
Intervention satisfaction evaluation
The physical performance or other indices of physical
performance
Anthropometric characteristics and
anthropometric evaluation
No information about PA effects
Timing
10-year publication date limit
English language
Full text available
Published before 2011
Not in the English language
No full text is available
Study design Experimental or observational study with original
primary data
Study protocol or other studies without
original data
Note: PA—physical activity.

Int. J. Environ. Res. Public Health 2022,19, 12482 3 of 15
A systematic literature search of the main coherent databases according to the aim of
this paper, MEDLINE (PubMed), Cochrane Central Register of Controlled Trials (Central),
CINAHL (EBSCO), and PSYCHINFO (EBSCO), from April 2022 up to May 2022 was
conducted to identify all published articles about PA interventions carried out in green
and blue spaces and relative effects in terms of physical fitness, quality of life, physical
performance, and anthropometric characteristics focusing on healthy adults.
Only randomized controlled trials (RCTs), case reports, clinical trials, observational
studies, and clinical trials for which the full text was available were included. In addition,
only human subjects were included, and we decided to put a 10-year publication date
limit. Search strategies (strings adapted when necessary in order to fit the specific search re-
quirements of each database) used the following Boolean expression, keywords, and terms
(terms mainly chosen from papers related to the topic and mesh database): (“Exercis*” OR
“Physical Activity” OR “Activities, Physical” OR “Activity, Physical” OR “Physical Activi-
ties” OR “Exercise, Physical” OR “Exercises, Physical” OR “Physical Exercise” OR “Physical
Exercises” OR “Acute Exercise” OR “Acute Exercises” OR “Exercise, Acute” OR “Exercises,
Acute” OR “Exercise, Isometric” OR “Exercises, Isometric” OR “Isometric Exercises” OR
“Isometric Exercise” OR “Exercise, Aerobic” OR “Aerobic Exercise” OR “Aerobic Exercises”
OR “Exercises, Aerobic” OR “Exercise Training” OR “Exercise Trainings” OR “Training,
Exercise” OR “Trainings, Exercise”) AND (“Outdoor Exercis*” OR “Outdoor Fitness” OR
“Outdoor Physical Activity” OR “Natural Environment Exercise” OR “Blue Space Physical
Activity” OR “Green Urban Space Exercis*” OR “Green Urban Space Physical Activity” OR
“Outdoor Training” OR “Outdoor Circuit Training” OR “Outdoor Resistance Training” OR
“Outdoor High Intensity Training” OR “Park Exercise” OR “Park Training”) AND (Adult
OR “Young Adult” OR “Healthy Adult” OR “Older Adult”) AND (“Health Outcomes” OR
“Anthropometric Outcomes” OR “Anthropometric characteristics” OR “Anthropometrical
outcomes” OR “Anthropometrical characteristics” OR “Wellbeing” OR “psycho-social
Wellbeing” OR “Quality of Life” OR “Physical Performance” OR “Physical Fitness”).
Moreover, hand searches of key conference proceedings, journals, and professional
organizations’ websites were conducted by SM, AG, and PML, and, in accordance with
the snowball technique, references cited in the primary papers were examined to discover
possible additional papers.
2.2. Quality Assessment and Data Extraction
Screening and checking phases followed different steps. First of all, the reviewers
(SM, AG, MM, and PML) independently and blindly screened eligible papers after the
removal of duplicates, reading titles, and abstracts to select pertinent papers. After the
first screening, the reviewers (SM, AG, and PML) retrieved and read the full text of all
potentially eligible studies. Disagreements about the eligibility of the studies for inclu-
sion were resolved through discussion between all the researchers’ groups, and if more
information was necessary, the study authors were contacted. Finally, the investigators,
following the standardized rules for literature collection given by the Cochrane Reviewers
handbook [
28
], independently obtained the information of the included studies focusing
on the following characteristics: author, country, study design, population, intervention,
outcomes, and results.
The studies included in the final step were independently and separately evaluated
for the risk of bias by researchers (AG and SM) using the “A revised Cochrane risk of
bias tool for randomized trials” (RoB 2) [
29
] and “The Risk Of Bias In Non-randomized
Studies—of Interventions (ROBINS-I) assessment tool” [
30
]. Any disagreement between the
quality scores separately assigned by the blind reviewers was resolved through discussion,
and, if necessary, two more blind reviewers belonging to the research team (MM and ST)
were involved as tiebreakers. This methodological choice was supported by the PRISMA
guidelines [27].
RoB-2 tool analyzes different biases in five domains: (1) bias resulting in the random-
ization process; (2) bias arising from deviations from intended interventions; (3) bias linked

Int. J. Environ. Res. Public Health 2022,19, 12482 4 of 15
to missing outcome data; (4) bias in the measurement of the outcome; and (5) bias on the
reported result. The response options for the reported questions in each domain are as
follows: yes, probably yes (PY), probably no (PN), no, and no information (NI).
These categories provide the possibility to assess an overall risk-of-bias judgment for
the specific study result being evaluated in low risk of bias, some concerns, and high risk
of bias.
The ROBINS-I scale uses seven different domains: (1) bias arising from confounding;
(2) bias in the selection of the study’s participants; (3) bias in intervention classification;
(4) bias linked to deviations from intended interventions; (5) bias resulting to missing data;
(6) bias due to the measurement of outcomes; and (7) bias on the reported result. The
response options for the domain level were the same as those of RoB-2, but the overall
risk-of-bias judgment includes low risk, moderate risk, serious risk, and critical risk of bias.
3. Results
3.1. Study Selection and Characteristics
Through database browsing and hand-searching, a total of 239 articles were identified
(Figure 1). Considering the articles identified from databases, three were excluded because
they were duplicated, and 157 were excluded after the reading of the abstract. Then, the
authors read the full text of the articles, and 69 were excluded because they matched the
exclusion criteria; finally, only six were considered relevant. All the records identified from
hand-searching were excluded after reading the full text.
Int. J. Environ. Res. Public Health 2022, 19, x FOR PEER REVIEW 5 of 14
Figure 1. PRISMA 2020 flow diagram of studies selection [31].
3.2. Risk of Bias Assessment
Each study was evaluated for quality assessment differentiating RCTs from
quasi-experimental studies. The five studies categorized as RCTs scored a risk of bias
from low to some concern, as shown in the Table 2 showing studies that resulted in low
risk [32–36] of bias and two with some concerns [34–37].
Considering the quasi-experimental study performed by Song et al. [32–37], the
response to the quality assessment was moderate concerns.
The major concerns were related to the second domain (risk of bias due to deviations
from the intended interventions) mainly because there were no blinding of participants
and people delivering the intervention given that it concerns physical activity practice
(item #2.2–2.3).
Table 2. Quality assessment of RCTs and quasi-experimental studies.
Authors Study Design Tool for Assessment Quality
Song et al. 2015 [32] Quasi-experimental ROBINS-I Scale Moderate concerns
Sales et al. 2017 [33] RCT RoB2 Tool Low risk
Plotnikoff et al. 2017 [34] RCT RoB2 Tool Some concerns
Kim et al. 2018 [35] RCT RoB2 Tool Low risk
Muller-Riemenschneider
et al. 2020 [36] RCT RoB2 Tool Low risk
Vert et al. 2020 [37] RCT RoB2 Tool Some concerns
RCT: randomized control trial; ROB2: Cochrane risk-of-bias tool for randomized trials; ROBINS-I:
the Risk Of Bias In Non-randomized Studies—of Interventions.
3.3. Data Extraction of the Included Study
Table 3 summarizes the principal aspects and results of the included studies
evaluating the effects of PA interventions on health outcomes in healthy people over 18.
Figure 1. PRISMA 2020 flow diagram of studies selection [31].
The main reasons for exclusion in the first step (abstract reading) were as follows:
no physical activity intervention was carried out in the study, and no healthy people
were involved. After the full-text reading (considering both reports from databases and
hand-searching), the main causes of exclusion were the implementation of physical activity
intervention carried out indoors and types of the study (without original primary data).

Int. J. Environ. Res. Public Health 2022,19, 12482 5 of 15
3.2. Risk of Bias Assessment
Each study was evaluated for quality assessment differentiating RCTs from quasi-
experimental studies. The five studies categorized as RCTs scored a risk of bias from low to
some concern, as shown in the Table 2showing studies that resulted in low risk [
32
–
36
] of
bias and two with some concerns [34–37].
Table 2. Quality assessment of RCTs and quasi-experimental studies.
Authors Study Design Tool for Assessment Quality
Song et al., 2015 [32] Quasi-experimental ROBINS-I Scale Moderate concerns
Sales et al., 2017 [33] RCT RoB2 Tool Low risk
Plotnikoff et al., 2017 [34] RCT RoB2 Tool Some concerns
Kim et al., 2018 [35] RCT RoB2 Tool Low risk
Muller-Riemenschneider
et al., 2020 [36]RCT RoB2 Tool Low risk
Vert et al., 2020 [37] RCT RoB2 Tool Some concerns
RCT: randomized control trial; ROB2: Cochrane risk-of-bias tool for randomized trials; ROBINS-I: the Risk Of
Bias In Non-randomized Studies—of Interventions.
Considering the quasi-experimental study performed by Song et al. [
32
–
37
], the re-
sponse to the quality assessment was moderate concerns.
The major concerns were related to the second domain (risk of bias due to deviations
from the intended interventions) mainly because there were no blinding of participants and
people delivering the intervention given that it concerns physical activity practice (item
#2.2–2.3).
3.3. Data Extraction of the Included Study
Table 3summarizes the principal aspects and results of the included studies evaluating
the effects of PA interventions on health outcomes in healthy people over 18. The geographic
origin of the studies was as follows: Australia (n= 2), Korea (n= 1), Japan (n= 1), Spain
(n= 1), and Singapore (n= 1). Study characteristics were heterogeneous. The sample size
varied from 23 to 160 people. Ages ranged from 22 to 80 years.

Int. J. Environ. Res. Public Health 2022,19, 12482 6 of 15
Table 3. Characteristics of studies included.
Study Study Design Population Intervention Outcome Results
Song et al. 2015,
Japan [32]
NRCT N: 23 men (aged 22.3 ±1.2,
height 171.1
±
4.7 cm, weight
63.4 ±8.1 kg, BMI
21.5 ±2.1 kg/m2)
Type: 15 min of walking in two
different environments—an urban
park and a city area; after walking,
the subject returned to the waiting
room and completed the
questionnaires. Participants rested
for approximately 20 min and
repeated the experiment in the
other environment. There were no
significant differences in the
average speed between the two
environments.
Frequency: twice a day
Time: 3 days
Physiological relaxation, three
different questionnaires were
used to investigate the
psychological responses after
walking in each site. The
questionnaires were the SD
scores, POMS, and STAI score.
Heart rate and its variability
were measured to investigate
automatic nerve activity i.
The participants showed statistically significant
differences in their physiological and
psychological responses to the walking in
different environments. The natural logarithm
of the HF component, which is an estimate of
the parasympathetic nerve activity, was higher
when subjects walked in the urban park than
when they walked in the city area. The mean
ln(HF) was significantly higher in the
urban-park walking than city-area walking
(p≤0.01). Then, the estimation of the
sympathetic nerve activity was lower during the
urban-park walking than city-area walking. The
mean heart rate was significantly lower in the
urban-park walking than city-area walking
(p≤0.01). A significantly higher SD score was
observed following the urban-park walking
than those following the city-area walking for
the three adjectives: comfortable, natural, and
relaxed. The negative subscale of
tension–anxiety, anger–hostility, fatigue, and
confusion was significantly lower after walking
in the urban park than walking in the city area
(p≤0.05). On the contrary, the positive mood
state vigor was significantly higher for walking
in the urban park (p≤0.001). The total STAI
score was 19.3% significantly lower after
walking in the urban park than after walking in
the city area (p≤0.01)

Int. J. Environ. Res. Public Health 2022,19, 12482 7 of 15
Table 3. Cont.
Study Study Design Population Intervention Outcome Results
Sales et al. 2017,
Australia [33]
RCT N: 48
CG: 21
(age 70.2 ±8.2, 77% women,
BMI 28.1 ±5.0, 6% current
smoker, 29% ex-smoker, 52%
daily alcohol assumption,
61.9% had previous falls
history, 47.6% had falls over
12 months)
EG: 27
(age 75.1 ±7.9, 64% women,
BMI 28.9 ±5.3, 3% current
smoker, 42% ex-smoker, 41%
daily alcohol assumption,
62.9% had previous falls
history, 40.7% had falls over
12 months)
Type: different kinds of outdoor
exercises with different exercise
stations: push-ups, modified
pull-ups, balance stool, sit to stand,
ramp + net + climb through,
balance beam, steps, step-ups or
taps on platform, gangway, calf
raises + finger steps, round snake
pipe, sharp snake pipe, hip
extension, screws and turners, and
hip abduction. Exercisers were
paired in stations, and an exercise
session could include up to eight
stations.
Frequency: two times a week,
approximately 1–15 h, with
5–10 min of warm-up, followed by
45–75 min on the equipment
station and 5–10 min of cool-down
exercises. Time: 18 weeks of
interventions
BOOMER test, to assess the
effectiveness of the exercise park
to improve balance; handgrip
strength, to measure the physical
strength; single leg test standing,
to measure the static balance;
2 min walk test, to assess
physical tolerance, functional
mobility; 30 min sit-to-stand test,
to evaluate the strength of the
knee extender muscle; feasibility,
defined as the number of
participants recruited and
retained over the recruitment
period; physical composite
scores, shortfalls efficacy scale
international, numbers of falls
over 12 months
No significant improvement in the BOOMER
test (CG, 13.5 ±1.7 pre, 13.9 ±1.4 post, p= 0.6
EG 13.6 ±1.4 pre, 13.7 ±1.3 post, p= 0.6, p
between groups = 0.4) and the improvement in
quality of life (CG 49.1 ±7.91 pre, 48.9 ±7.6
post, p= 0.2, for the physical component,
51.4 ±6.1 pre, 51.6 ±7.9 post, p= 0.6, for the
mental component; EG 46.9
±
7.6 pre, 49.6
±
8.3
post, p= 0.4, for the physical component,
53.1 ±9.8 pre, 54.5 ±7.0 post, p= 0.6, for the
mental component) and falls efficacy (CG
11.3 ±4.0 pre, 10.9 ±3.7 post, p= 0.4, EG
10.3 ±3.4 pre
, 9.3
±
2.5, post, p= 0.4, pbetween
groups = 0.1). EG showed significant
improvements in knee strength (84.2
±
36.5 pre,
96.4 ±44.4 post, p= 0.01), balance (single leg
stance, 15.6 ±11.0 pre, 17.3 ±11.3 post,
p= 0.01), 2 min walk test (140.6 ±30.5 pre,
152.1 ±28.7 post, p= 0.01), and sit to stand
(10.5 ±3.0 pre, 12.1 ±2.7 post, p= 0.01).
Regarding feasibility, 87% of EG completed the
18-week intervention with mean attendance to
the session of 79.6% and 14% of the CG attended
the social meeting offered.

Int. J. Environ. Res. Public Health 2022,19, 12482 8 of 15
Table 3. Cont.
Study Study Design Population Intervention Outcome Results
Plotnikoff et al.
2017, Australia
[34]
RCT N:84
(aged 44.7 ±14.0, BMI
33.3 ±5.7 kg/m2)
CG: 42, aged 45.1
±
14.7, BMI
31.7 ±5.1 kg/m2,
EG: 42, aged 44.2
±
13.5, BMI
35.0 ±5.9 kg/m2
Type: EG—five face-to-face group
intervention, each intervention
lasted for 90 min and consisted of
30 min of cognitive group and
60 min of small group outdoor
training and outdoor PA with the
eCoFit smartphone app that
included workout circuits, and a
description of where and how to
use an outdoor physical
environment to be more physically
active.
CG: no interventions
Frequency: once a week
Time: 20 weeks of interventions;
phase 1: 1–10 weeks face-to-face
group intervention; phase 2:
11–20 weeks eCoFit
smartphone app
Aerobic fitness to assess aerobic
fitness; lower body muscular
fitness using the chair stand test;
steps/day measured using
pedometers; functional mobility
using the Timed Up and Go test;
waist circumferences, BMI, and
systolic and diastolic blood
pressure
After 10 weeks, EG improved aerobic fitness
(4.50 mL/kg/min), the strength of the lower
body, numbers of steps (1330 steps), mobility
(−1.8 s), and systolic blood pressure, and there
was a decrease in waist circumference (
−
2.8 cm).
After 20 weeks, EG showed effects on the upper
and lower body strength, blood pressure, and
functional mobility.
Survey conducted at the end of the intervention
showed positive feedback for group cognitive
session, outdoor training, and use of the
eCoFit app.
Kim et al. 2018,
South Korea [
35
]
RCT N: 35
(aged 73.20 ±4.90, women
characteristics (32): BMI
25.48 ±2.41, kg/m2height
151.98 ±5.90 cm, weight
58.73 ±8.19 kg, lean mass
19.64 ±2.50 kg, body fat
36.84 ±3.36%; men
characteristics (3): BMI
24.70 ±2.87 kg/m2, weight
69.40 ±8.39 kg,
168.20 ±4.75 cm, lean mass
27.00 ±3.72 kg, body fat
28.66 ±3.95%)
RC: 12,
CoG: 13
CG: 10
Type: RC—outdoor resistance
training using leg extension, pull
weight, chair pull, for a total of 50
min of training;
CoG: outdoor aerobic and
resistance training using leg
extension, pull weight, chair pull,
sky-walker, cross-country, for a
total of 70 min;
CG: no interventions
Time: 6 weeks of interventions at
different intensity evaluated with
the Borg scale
Fitness was evaluated with five
fitness tests designed for the
elderly (30 s chair stand,
30 s arm curl, 244 cm up and go,
one-leg stand, and 2 min step), as
well
as number of pushups and
6 min walking
Improvement in upper-body strength in both
groups (RC 19.16 ±11.40 pre, 30.16 ±13.13
post; CoG 11.07 ±9.62 pre, 22.23 ±12.95 post);
lower-body endurance was higher in the CoG
(561.84 ±67.22 m) than the CG
(486.44 ±96.14 m).

Int. J. Environ. Res. Public Health 2022,19, 12482 9 of 15
Table 3. Cont.
Study Study Design Population Intervention Outcome Results
MullerRiemns-
chneider et al.
2020, Singapore
[36]
RCT N: 160 (aged 51.1 ±6.3,
127 women, total MVPA
442.7 ±534.7 min/week)
EG: 80 (aged 52.1 ±6.5,
65 women)
CG: 80 (aged 50.0 ±6.0,
62 women)
Type: EG—face-to-face counseling
on PA; they completed a park
prescription sheet where they
committed to a goal that specified
the frequency, intensity, time, and
location of exercise parks.
Participants received two
brochures developed for the trial:
one provided information on the
main parks and their different
features, including walking trails
and location of fitness corners. The
second was generally about the
Singapore National Park s Board.
+ invitation to weekly exercise
sessions in parks; in addition,
participants received half-way
through the trial a brief counseling
phone call to assess progress and
included modification of the goal if
necessary. CG: continued their
daily routine; they received
standard PA materials.
Time: 6-week intervention.
Time spent on MVPA measured
by an accelerometer and by
questionnaire, total volume of
PA, time spent on light and
sedentary activity, time spent at
the park, physical activity at the
park, recreational MVPA, mental
well-being (measured by SF-12,
K-10, WHO5, and
WHOQOL-BREF).
No differences between EG and CG were
observed with regard to physiological distress
and overall quality of life. The only difference
was found for the psychological quality of life,
which was higher in EG than in CG (p= 0.047).
The difference was not statistically significant
regarding the mean differences in MVPA among
participants. EG showed a significant increase in
the time of recreational PA (EG
142 ±155.4 min/week, CG
93.6 ±131.0 min/week
,p= 0.044), time spent in
parks (EG 333.9 ±506.2 min/month, CG
186.4 ±85.4 min/month, p= 0.047), and PA in
parks (EG 333.0 ±499.3 min/month, CG
140.5 ±270.7 min/month, p= 0.005).

Int. J. Environ. Res. Public Health 2022,19, 12482 10 of 15
Table 3. Cont.
Study Study Design Population Intervention Outcome Results
Vert et al. 2020,
Spain [37]
RCT N: 49 (aged 29, min 19, max
49, 69.5% women, BMI
22.6 ±3.5 kg/m2, 88.1% saw
blue space at work, 89.9% met
the PA of WHO guidelines)
Type: for each study week, each
participant was assigned to a
different environment (blue, urban,
or control site). All participants
were exposed to all environments
upon completion of the study.
They walked 20 min in blue, urban,
or control site. Participants were
distributed in two turns: the first
started at 10.00 a.m. and the
second at 11.30 a.m.
Frequency: 4 days a week
Time: 3 weeks intervention
Participants completed a set of
questionnaires (SWB, WHO-5,
TMD, 4SDQ, and SF-36) to
assesses their well-being, mood,
and psychological responses,
before and after each walking. In
addition, sleep characteristics
and general health were assessed.
Blood pressure, pulse rate, and
heart rate variabilities were
continuously measured before
and after the walking.
Better well-being and mood responses after
walking in a blue space versus an urban space
or control site (p≤0.05). For SWB, no
significant differences were found. For WHO-5,
the “total well-being score” was increased when
participants were exposed to blue environment
(p≤0.05). TMD was significantly lower for the
negative subscales after walking along the blue
route compared with urban space and control
site (p≤0.05). 4SDQ did not show significant
differences between the environments.
Statistically significant increase was found in
systolic blood pressure and pulse rate in the
blue and urban environments compared with
the control site. Increase in SNS activity during
and after walking in blue and urban spaces.
RCT: randomized control trial; NRCT: nonrandomized control trial; N: numbers of participants; CG: control group; EG: experimental group; RC: resistance group; CoG: combined
group; PA: physical activity; BOOMER: Balance Outcome Measure for Elder Rehabilitation; min: minutes; SD: semantic differential; POMS: profile of mood state; STAI: state–
trait anxiety inventory, MVPA: moderato-to-vigorous physical activity; PA: physical activity; SWB: subjective well-being; TMD: total mood disturbance; 4SDQ: four-dimensional
symptom questionnaire.

Int. J. Environ. Res. Public Health 2022,19, 12482 11 of 15
We extracted the intervention characteristic by adopting the “F.I.T.T.” classification
(frequency, intensity, time, type) mainly used in exercise prescription [38].
The duration of the experimental design varied from 3 days to 20 weeks and the
frequency from two to seven times a week. The “type” of the intervention included two
studies involving walking intervention [
36
,
37
], two studies involving a combination of
resistance training and aerobic were used [
33
,
35
], and two studies involved resistance
training [
32
,
34
]. According to this, the outcomes were heterogeneous, varying from perfor-
mance tests such as balance test and handgrip test to well-being and quality of life assessed
through a questionnaire. Table 3describes the details of the included studies.
4. Discussion
The present systematic review was aimed at investigating the existing evidence
regarding the effects of PA interventions carried out in GBS involving healthy people
(
aged ≥18 years
). While research has previously assessed how GBS affects health and
physical well-being, the relationship between exposure and health effects for healthy peo-
ple is not well-known. For this reason, the aim of the present systematic review was to
investigate the existing evidence regarding the effects of PA interventions performed in a
natural environment involving healthy people (aged ≥18 years).
The systematic research of the literature found six studies, with different kinds of
interventions and outcomes. The six eligible studies were scored as of medium quality
and showed several improvements in health outcomes, which will be investigated in the
present section.
Among the PA interventions adopted in the included studies, walking is a cost-
effective one, which might appeal to most of the population [
39
]. In connection with
this, walking in a blue space and in an urban park showed better well-being and mood
responses compared with walking in an urban space or resting in a control site [
32
,
36
,
37
].
Song et al. (2015) reported significant differences in the questionnaires administered during
the study [
32
]. In fact, the SD score was higher after walking in an urban park for three
adjectives: comfortable, natural, and relaxed (p
≤
0.05), and lower for the negative subscales
tension–anxiety, anger–hostility, fatigue, and confusion (p
≤
0.05). Finally, the positive
mood state vigor was significantly higher for walking in the urban park than for the city-
center walk (p
≤
0.05). Song et al. (2015) did not report the effect size, but they used the
Wilcoxon signed-rank test to analyze differences in psychological indices reported after
walking in the two environments. Vert et al. (2020) found similar results for the blue space.
In fact, participants showed better well-being and mood response after walking in a blue
space versus an urban space or a control site (p
≤
0.05). The WHO-5 total well-being score
increased when participants were exposed to a blue environment (p
≤
0.05). In addition,
Vert et al. (2020) did not report the effect size, and they used mixed-effects regression
models to evaluate the difference linked to the environment. One of the easiest ways to
be and remain active is walking, and it is also the most popular [
40
]. A study found that
adults who achieved the right amount of PA observed that walking was the most reported
activity [
40
]. This could be due to its accessibility. Walking is a universal form of PA
that a large part of the population can practice without differences in age, sex, education,
income level, or ethnic group. Expensive equipment, special skills, or special facilities are
not required in walking. There is an inverse association between the risk of developing
coronary heart disease and overall walking in women [
41
]. In addition, walking is an
important activity for older people. In fact, walking outdoors at least once a week has
been associated with achieving more time spent in moderate to vigorous PA than walking
indoors [
42
], and it also provides a way to take part in relevant activities, such as shopping
or leisure activities (e.g., visiting friends or pleasure walking). Being physically active is
linked to substantially lower costs of medical care [
43
], and, in particular for older adults
where the risk of chronic disease is higher, walking has the potential to reduce medical
expenditure [
44
]. In this review, two studies used walking as an intervention; they had
similar objectives even if they used different questionnaires to evaluate the psychological

Int. J. Environ. Res. Public Health 2022,19, 12482 12 of 15
answers to walking in a different kind of environment [
32
,
36
,
37
]. In particular, the first
article aimed to value psychological and cardiovascular responses of the exposure to blue
space, urban space, and a control site and to value whether well-being and mood effects
were constant for (at least) four hours after exposure [
36
,
37
]. The second article would
clarify the physiological effects of walking in urban parks during fall (autumn) [
32
,
37
].
Both articles found positive effects after the period of interventions, so they seem to suggest
that walking in a natural environment had multiple positive effects. However, more studies
are needed to improve the knowledge about this topic.
Concerning performance outcomes, resistance training induced significant improve-
ment in body muscular strength, aerobic fitness, number of steps, functional mobility,
systolic blood pressure, and waist circumference in the experimental group than in the
control group [
33
–
35
]. In two studies, outdoor fitness equipment was used [
32
,
33
,
35
].
Several studies showed that outdoor fitness equipment has become very popular world-
wide in numerous green and blue spaces and built-up environments [
45
–
49
]. Outdoor
fitness equipment (OFE) can be used by a large part of the population (there is also OFE
adapted for people in wheelchairs) because it provides free access to fitness training for the
community and also enables different kinds of training (e.g., resistance training or circuit
training) [
42
,
48
,
49
]. The results of the use of outdoor fitness equipment are mixed. Sales
et al. found significant improvements in knee strength, balance, 2 min walk test, and sit to
stand [
31
]. Meanwhile, Kim et al.’s study showed significant improvement in the upper-
body strength. These differences in the results are linked to the different kinds of outdoor
fitness equipment used. In fact, there are different manufacturers that design and produce
outdoor fitness equipment, with differences in shape, materials, size, or smoothness of
operation [6].
Plotnikoff et al. and Muller-Riemenshneider et al. evaluated the effects of PA in green
and blue spaces and the effectiveness of face-to-face counseling [
34
–
36
]. In both studies,
the participants received information about the parks in their city or their neighborhood to
promote the use of a kind of environment. Plotnikoff et al. used a smartphone application,
called eCoFit, in which the participants of the experimental group could find workout
circuits suited for several geographical locations in the city. Indeed, in the study of Muller-
Riemenshneider et al., the participants received an information brochure and a sheet where
they filled in the types of activities they aimed to do each week over the trial period [
34
,
36
].
Even if the study design is similar between the two studies, the results are not comparable
because they used different types of exercises and different questionnaires, and the time of
the study was different. However, both studies found positive effects of the interventions.
The experimental group in Muller-Riemenshneider et al.’s study was asked to join one
hour of an outdoor structured and supervised PA program every week in a park. The
control group received only standard PA promotion materials. At the end of six months,
the experimental group had a significant increase in recreational PA, time spent in parks,
and PA in parks. Additionally, they achieved improvements in chosen measures of quality
of life and well-being, especially the psychological quality of life. Plontikoff et al.’s study
divided into two parts the design for the intervention group: for 10 weeks, the participants
performed personal sessions and used the app for smartphones; then, for the other 10 weeks,
they used only the smartphone app. Most of the improvement related to health outcomes
at 10 weeks was also confirmed at 20 weeks. This suggests that the participants continued
the PA during phase 2. One of the key objectives was to promote the use of local green
spaces, and eliminating many of the common barriers to participating can be interesting to
verify if, after a longer period (a year), the participants of the intervention group continued
to use the green spaces as a place to do PA. Despite several pieces of evidence on the
health benefits of green and blue spaces, they are generally underused [
21
,
50
], so it can be
important to sensitize the population more about the potential of this kind of environment.
From a public health perspective, these results can represent a strategy to be imple-
mented to make the most of the natural setting to amplify the benefits of physical activity
practice with a view to preventing health risks and saving resources. In connection with

Int. J. Environ. Res. Public Health 2022,19, 12482 13 of 15
this, a recent systematic review recommends for future policies and research to take a more
integrated multisystem approach and be inclusive of local and spatial authority planning
and meet the needs of transport and natural resources [9].
The concept of “blue space” has not been widely used compared with green space,
even if some studies demonstrated the potentially higher effects of blue space on people’s
health. For this reason, it would be important that future studies propose physical activity
programs in blue spaces to more consistently verify the benefits of this type of environment.
5. Conclusions
In conclusion, the current systematic review found that physical activity interventions
including exercise and simple activities, carried out in an outdoor green–blue space natural
environment, can have a positive impact on a healthy population, both after a few weeks
of intervention or after several weeks, and can be an effective strategy to enhance and
promote healthy lifestyles.
No exhaustive conclusion can be drawn based on available evidence. However, this
systematic review highlighted the need to extend this kind of intervention that might
stimulate a change in adults’ lifestyles, involving also their mood and job spheres. This
approach can represent future effective integrative strategies to gain more benefits by
practicing physical activity in natural green and blue spaces.
Author Contributions:
S.M. and P.M.L. conceived and designed the systematic review; S.M., A.G.
and P.M.L. independently reviewed abstracts and papers, and disagreements were resolved by
consensus with M.M. and S.T.; S.M. and A.G. acquired, analyzed, and interpreted the data; M.M.,
S.T. and P.M.L. checked data extractions; S.M. drafted the manuscript, which was critically revised
for important intellectual content by all authors; A.G. wrote sections of the manuscript; M.M., S.T.
and P.M.L. revised the manuscript and contributed intellectual ideas. S.T. and P.M.L. supervised the
study. All authors have read and agreed to the published version of the manuscript.
Funding: This research received no external funding.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: The data presented in the study are included in the article.
Conflicts of Interest: The authors declare no conflict of interest.
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