Outdoor Time Is Associated with Physical Activity, Sedentary Time,
and Cardiorespiratory Fitness in Youth
Lee Schaefer, PhD1, Ronald C. Plotnikoff, PhD2, Sumit R. Majumdar, MD, MPH3,4, Rebecca Mollard, PhD5,
Meaghan Woo, BSc5, Rashik Sadman5, Randi Lynn Rinaldi, MSc6, Normand Boule, PhD6, Brian Torrance, MSc7,
Geoff D. C. Ball, PhD, RD8, Paul Veugelers, PhD3, Paul Wozny, EdD9, Linda McCargar, PhD10, Shauna Downs, MSc11,
Richard Lewanczuk, MD, PhD5, Douglas Gleddie, PhD12, and Jonathan McGavock, PhD5
Objective To determine whether time spent outdoors was associated with increased moderate-to-vigorous
physical activity (MVPA) and related health benefits in youth.
Study design We performed a cross-sectional study of 306 youth aged 13.6 1.4 years. The exposure of interest
was self-reported time spent outdoors after school, stratified into three categories: none, some, and most/all of
the time. The main outcome of interest was accelerometer-derived MVPA (Actical: 1500 to >6500 counts/min).
Secondary outcomes included sedentary behavior, cardiorespiratory fitness, overweight status, and blood pressure.
Results Among the 306 youth studied, those who reported spending most/all of their after-school time outdoors
(n = 120) participated in more MVPA (61.0 24.3 vs 39.9 19.1 min/day; adjusted P < .001), were more likely to
achieve the recommended minimum 60 min/day of MVPA (aOR 2.8; 95% CI, 1.3-6.4), spent less time in sedentary
activities (539 97 min/day vs 610 146 min/day; adjusted P < .001), and had higher cardiorespiratory fitness
(49 5 vs 45 6 mL/kg/min; adjusted P < .001) than youth who reported no time outdoors (n = 52). No differences
in overweight/obesity or blood pressure were observed across the groups.
Conclusions Time spent outdoors is positively associated with MVPA and cardiorespiratory fitness in youth and
negatively associated with sedentary behavior. Experimental trials are needed to determine whether strategies
designed to increase time spent outdoors exert a positive influence on physical activity and fitness levels in youth.
(J Pediatr 2014;-:---).
V
ery few youth living in developed countries achieve the recommended minimum of 60 minutes of moderate-to-vigorous
physical activity (MVPA) daily.1 The low levels of physical activity among children and adolescents are attributed to
several factors, including changes in the built environment,2 increased availability of electronic gaming and computers,3
and possibly reductions in the time spent outdoors.4 Studies by our group5 and others6,7 reveal that youth accumulate the
majority of their MVPA during school hours. Specifically, we found that children accumulated 25% more minutes of
MVPA on school days relative to weekend days or holidays.5,6 In fact, children achieve on average only 10 minutes of
MVPA during the after-school period (3:00-5:00 p.m.).7 Several expert groups have called for increasing outdoor time as
one strategy to increase physical activity levels in children during the after-school time period.8,9 Two key observations
have initiated calls for more outdoor activities: (1) children accumulate little MVPA during after-school hours; and
(2) levels of outdoor play for children have decreased considerably over the
past 20 years.8,10,11
Unfortunately, the evidence supporting these calls is lacking and few
From the Faculty of Education, University of Regina,
Regina, Saskatchewan, Canada; Priority Research
well-controlled studies have documented a link between time spent outdoors
Center in Physical Activity and Nutrition, The University of
and health behaviors in children.12,13 The few studies published to date on this
Newcastle, Newcastle, New South Wales, Australia;
School of Public Health, Department of Medicine,
topic are generally restricted to younger children, relied on parental report of
University of Alberta, Edmonton, Alberta, Canada;
Department of Pediatrics and Child Health, Manitoba
outdoor activity, and have not adequately addressed possible confounding
Institute of Child Health, University of Manitoba,
8,10,11
Winnipeg, Manitoba, Canada; Faculty of Physical
factors (eg, sex, season, weight status).
Education and Recreation, University of Alberta; Ever
To overcome limitations of previous studies and to determine whether time
Active Schools; Department of Pediatrics, University of
Alberta, Edmonton, Alberta, Canada; Black Gold School
spent outdoors during the after-school hours was positively associated with
District, Alberta, Canada; Faculty of Agricultural, Life
and Environmental Sciences, University of Alberta,
MVPA and related health outcomes in youth, we performed a cross-sectional
Edmonton, Alberta, Canada; Menzies Center for Health
study of youth 9-17 years of age enrolled in the Healthy Hearts Prospective
Policy, University of Sydney, Sydney, Australia; and
Faculty of Education, University of Alberta, Edmonton,
Cohort Study of Physical Activity and Cardiometabolic Health.14,15 We hypothAlberta, Canada
esized that: (1) time spent outdoors would be positively associated with MVPA;
Supported by the Canadian Diabetes Association, the
1
2
3
4
5
6
7
8
9
10
11
12
Alberta Center for Child, Family, and Community
Research, the Canadian Institutes of Health Research,
and the Manitoba Health Research Council. The authors
declare no conflicts of interest.
BMI
MVPA
Body mass index
Moderate-to-vigorous physical activity
0022-3476/$ - see front matter. Copyright ª 2014 Elsevier Inc.
All rights reserved.
http://dx.doi.org/10.1016/j.jpeds.2014.05.029
1
THE JOURNAL OF PEDIATRICS
www.jpeds.com
and (2) youth who reported spending most or all of their
time outdoors after school would be less sedentary and
have greater cardiorespiratory fitness than their peers who
spent little or no time outdoors during this period.
Methods
Data from youth who provided valid accelerometer data
(minimum of 3 days of wear time with at least 8 hours of
registered minutes per day14) and completed a questionnaire
regarding time spent outdoors from the 2009 wave of the
Healthy Hearts Prospective Cohort Study of Physical Activity
and Cardiometabolic Health were used in this study.14,15 The
prospective cohort study originally was designed to
determine the association between cardiorespiratory fitness
and the risk of overweight status in youth. The study involved
annual measures of anthropometrics (height, weight,
waist-to-hip ratio), cardiorespiratory fitness, and systolic
blood pressure in a school-based cohort of children and
adolescents (9-17 years of age) attending schools within the
Black Gold School District, for 3 years (2008-2010). Data
from this study as well as a more in depth description of
the methods used have been published previously.14,15 A
convenience sample of 591 youth aged 9-17 wore an
accelerometer and completed an online survey (WebSpan)16 in the 2009 wave of data collection.
Data for exposure and outcome variables were not
available for a sufficient number of youth in all 3 waves;
therefore, the data presented here are restricted to the wave
with the largest sample size that provided complete data.
Data-collection procedures for the larger cohort study have
previously been described.14 All parents and youth provided
written informed consent and assent, respectively, before
initiation of the study, in accordance with the Declaration
of Helsinki. This study was approved by the Human Research
Ethics Board at the University of Alberta (Edmonton,
Alberta, Canada).
During class time, youth completed a validated web-based
questionnaire of health behaviors that included a selfreported measure of time spent outdoors.16,17 This measure
was meant to encompass all time spent out of doors, after
the school period, whether taking part in organized activities,
or free play. Students were asked to recall the amount of time
spent outdoors during the afterschool period over the past
7 days with 4 possible responses: (1) none of the time; (2)
some of the time; (3) most of the time; and (4) all of the
time. As there were few responses for the fourth option, we
collapsed answers for option 3 and 4 into a single exposure
of “most/all of the time.” The exact time period that makes
up the after-school period was not specified in this question.
The primary outcome measure (MVPA) was determined
from 15-second epochs using waist-mounted accelerometers
worn over a period of 7 days (Actical, serial nos. B101270B101375; Respironics, Bend, Oregon) in the winter and spring
terms of the 2008/2009 academic calendar year. Raw physical
activity counts were converted into minutes of physical
activity with the Kinesoft software program (KineSoft,
2
Vol. -, No. Saskatoon, Saskatchewan, Canada).18,19 Participants who
failed to obtain a minimum of 3 days of wear with at least
480 registered minutes (8 hours) per day and the absence of
consecutive zero counts >60 minutes were excluded from
analyses. Similar criteria have been used in previous studies
by our group and others to estimate habitual physical activity
from accelerometer-derived data.14,20-22 Standardized
thresholds were used to classify raw counts per minute
(cpm) into intensities of physical activity: (1) sedentary
time (<100 cpm); (2) light-intensity (100-1499 cpm); (3)
moderate-intensity (1500-6499 cpm); and (4) vigorousintensity (>6500 cpm).1,23 Secondary outcomes included:
(1) sedentary behavior derived from accelerometry; (2)
cardiorespiratory fitness determined using the Leger shuttle
run15,24; and (3) systolic blood pressure assessed in triplicate
using an automated machine after 5 minutes of quiet sitting15
and overweight status determined from age- and sex-specific
thresholds for absolute body mass index (BMI) values to
classify youth as “healthy weight,” “overweight,” or “obese”
according to the International Obesity Task Force guidelines.25 Blood pressure also was treated as a categorical
variable with youth stratified as high normal if systolic blood
pressure was >90th percentile for age, sex, and height.
Age,26 sex,5 weight status,7 and season27 (cold season:
November-March; warm season: April-October) when physical activity was undertaken were considered potential confounders. Body weight was measured to the nearest 0.1 kg
in duplicate using a digital scale (Seca 882 Digital Floor scale;
Seca, Hamburg, Germany), and height was measured in
duplicate to the nearest 0.1 cm using a medical standard stadiometer (Seca Portable Model 214). Absolute BMI (kg/m2)
was converted to an age- and sex-specific Z-score using
EpiInfo.28 Waist circumference was measured using a flexible
tape at the top of the iliac crest as previously reported.
Statistical Analyses
Independent t tests were used to test for group-wise differences in characteristics between youth who were included
in the analysis and those who were excluded for lack of sufficient accelerometer data to test for potential sampling
bias. Normally distributed variables were compared across
levels of outdoor time using ANOVA. Non-normally distributed variables were compared across levels of outdoor time
using Kruskal-Wallis tests. Pearson c2 tests were used to
determine differences in categorical variables across levels
of outdoor time. Any significant differences in outcome
measures in unadjusted tests were repeated with multivariable general linear or logistic regression models, adjusting
for wear time, sex, age, BMI Z-score, and time of year.
In an effort to improve precision of the association, we
conducted a second series of analyses where the outcome
variable (MVPA) was restricted to the window of time
when they were queried about the time they spent outdoors
(3:30-11:59 p.m.). A multivariable linear regression model
was used to determine whether the time spent outdoors
was associated with MVPA and secondary outcome measures
independent of confounding variables. The odds of achieving
Schaefer et al
- 2014
ORIGINAL ARTICLES
$60 minutes of MVPA during the data collection period
across categories of outdoor time were determined by a
multivariable logistic regression adjusting for covariates. To
adjust for the confounding effects of sex and season we
employed a stratification approach,29 testing for associations
between exposure and outcome variables for boys and girls
and seasons (warm months vs cold months) separately. All
analyses were completed using SPSS version 20 (SAS Institute
Inc, Cary, North Carolina). A 2-tailed P < .05 was considered
statistically significant.
Results
Of the original 591 participants included in the 2009 wave of
the cohort study, 306 provided valid accelerometer and outdoor activity data. Of those 306, 52 (17%) reported spending
no time outdoors after school, 134 (44%) reported spending
some time outdoors, and 120 (39%) reported to having
most/all of their time spent outdoors. Compared with those
who provided valid data, those who did not were younger
(13.0 1.6 years vs 13.6 1.4 years, P < .001), but no differences in sex, cardiorespiratory fitness, BMI Z-score, or MVPA
were observed between those included in the analysis and
those who failed to provide adequate data. Among the youth
retained in the analysis, 58% were girls, 24% were overweight
or obese, 34% achieved an average of 60 min/day of MVPA,
and they provided an average of 5.1 1.4 days and
790 138 min/day of valid accelerometer data.
Participant characteristics stratified by self-reported time
outdoors are presented in Table I. Compared with those
reporting never being active outside, youth who reported
spending most/all of their time outdoors were younger
(13.3 vs 14.3 years, P < .001), more likely to be male (51%
vs 31%, P = .03), and contributed data during the warm
months of data collection (60% vs 33%, P = .001). No
group differences in BMI Z-score were noted.
MVPA increased and sedentary time decreased in a doseresponse manner with increasing time spent outdoors
(Table I). Specifically, youth reporting no time spent
outdoors achieved 21 fewer minutes of MVPA daily
(P < .001) and an additional 70 min/day of sedentary
behavior (P < .001) compared with youth who reported
spending most or all of their after-school time outdoors.
The strength and dose-response nature of the association
remained significant when analyses were repeated in
subgroups of youth stratified by sex and season (Figure 1).
In a multivariate regression analysis, outdoor time was a significant predictor of MVPA in youth, independent of age, sex,
BMI Z-score, fitness level, sedentary time, and season
(Table II). Time spent being sedentary (min/day) and
cardiorespiratory fitness (run score classification) also were
significant determinants of time spent in MVPA (Table II).
The odds of achieving >60 minutes of MVPA was 2.8-fold
greater for those who spent most or all of their after-school
time outdoors vs those who spent no time outdoors; however,
this relationship was dependent on whether the time spent
outdoors occurred on weekdays or weekend days (Table III).
When analyses were restricted to the after-school period,
which we defined as the hours between 3:30 and 11:59
p.m., the strength of the associations between outdoor time
Table I. Participant characteristics compared across the tertiles of time spent outdoors
Outdoor exposure
Variables
None of the time (n = 52)
Some of the time (n = 134)
Most/all of the time (n = 120)
P value
Age, y
Female/male, %
Weight, kg
BMI Z-score
Overweight/obese, %
Waist circumference, cm
Run score
VO2max, mL/kg/min
Fit/not fit, %†
Warm/cold months, %z
Valid days, no.
Valid minutes, min/d
Sedentary time, min/d
Light activity, min/d
Moderate activity, min/d
Vigorous activity, min/d
Total MVPA, min/d
>60 min/d total
Weekday MVPA, min/d
> 60 min/d weekday
Weekend MVPA, min/d
>60 min/d weekend
14.3 1.5
69/31
54.8 11.6
0.28 .94
21.5
74 10
6.2 2.2
44.8 5.6
48/52
33/67
5.0 1.3
790.4 138.4
609.9 145.5
151.9 66.0
37.0 17.2
2.9 4.2
39.9 19.1
19%
41.6 18.5
19%
31.3 24.7
13%
13.5 1.3*
60/40
54.0 12.7
0.46 0.90
27.8
73 70
6.9 2.2
47.8 5.7*
54/46
41/59
5.0 1.4
784.3 123.7
573.1 108.0
164.5 64.7*
48.8 20.0*
3.9 5.8
52.7 23.3*
31%
57.0 23.0*
37%*
38.5 33.5
12%
13.3 1.3*
49/51*
52.0 14.3
0.36 0.94
20.8
72 10
7.1 2.1*
48.7 5.4*
55/45
60/40*,x
5.1 1.4
789.9 137.6
538.5 97.2*
180.7 94.3*,x
57.0 22.5*,x
4.0 4.0*
61.0 24.3*,x
44%*
66.5 29.7*,x
50%*,x
43.3 29.1
19%
<.001
.03
.10
.45
.61
.06
.03
<.001
.72
<.001
.89
.75
<.001
<.001
<.001
.01
<.001
.004
<.001
.001
.09
.26
VO2max, maximal oxygen uptake.
*P < .05 vs none of the time.
†Those who were identified as fit had a run score classification of 4-5 and not fit had a run score classification of 1-3.
zSeason was separated into warm and cold data-collection months (April-October vs November-March).
xP < .05 vs some of the time.
Outdoor Time Is Associated with Physical Activity, Sedentary Time, and Cardiorespiratory Fitness in Youth
3
THE JOURNAL OF PEDIATRICS
Vol. -, No. -
www.jpeds.com
Table III. Odds of meeting the current MVPA
recommendation (>60 minutes of MVPA/d) with
increasing amounts of time spent outdoors*
MVPA
Total
None of the time
Some of the time
Most/all of the time
Weekday
None of the time
Some of the time
Most/all of the time
Weekend
None of the time
Some of the time
Most/all of the time
OR (95% CI)
P value
1.00 (ref)
1.63 (0.73-3.64)
2.84 (1.27-6.36)
.23
.01
1.00 (ref)
2.53 (1.14-5.59)
4.12 (1.84-9.24)
.02
.001
1.00 (ref)
0.45 (0.68-0.25)
0.67 (1.24-0.47)
.45
.67
*Analyses were adjusted for wear time, sex, age, BMI Z-score, and time of year.
Figure 1. Participant characteristics stratified by A, sex and
B, season. Error bars are SEM. *P < .05.
and both MVPA (Figure 2) and sedentary time was
significantly greater. Specifically, daily MVPA during the
after-school period was 57% greater (P # .001) in youth
who reported spending all/most of their time outdoors
compared with those reporting spending none of their time
outdoors, although it was only 31% greater (P = .001)
between the same groups of youth during school hours.
Similarly, sedentary time was 8.2% (232 vs 253 minutes;
P = .020) lower during the after-school period and 2.5%
(P = .3) lower during school hours in youth reporting
spending a lot of time outdoors compared with those
reporting no time spent outdoors.
Secondary End Points
In fully adjusted analyses, youth who reported spending most
or all of their after-school time outdoors accumulated less
sedentary time (540 105 min/day vs 610 106 min/day;
Table II. Determinants of time spent in MVPA, min/d
Model
b (95% CI)
Age, y
0.48 (1.36 to 2.33)
Sex
10.11 (4.95-15.27)
BMI Z-score
2.77 (0.04-5.50)
Season*
11.78 (6.76-16.80)
Run score class
3.35 (1.50-5.20)
Outdoor activity, min/d
4.85 (1.76-7.95)
Sedentary total, min/d 0.05 (0.08 to 0.03)
P
Standardized b value
0.03
0.20
0.10
0.24
0.20
0.16
0.25
.61
<.001
<.05
<.001
<.001
.002
<.001
*Season was separated into cold and warm data-collection months (November-March vs AprilOctober).
4
P < .001), had greater cardiorespiratory fitness (maximal oxygen uptake: 48.3 5.2 mL/(kg$min) vs 45.0 5.2 mL/
(kg$min); P < .001), and achieved greater shuttle run scores
(final run stage: 7.1 1.9 vs 5.9 1.9 minutes; P = .03)
compared with youth who reported spending no time
outdoors (Table I). No differences in BMI Z score were
noted across the groups; however, there was a trend towards
a lower waist circumference with increasing time spent
outdoors (Table I). No differences in the prevalence of
overweight/obesity (20.8% vs 21.5%; P = .61) or high blood
pressure (6.7% vs 7.8%; P = .90) were found based on the
amount of time youth spent outdoors.
Discussion
The data presented here suggest that outdoor time is a correlate of physical activity behavior in youth aged 9-17 years.
The data expand on previous studies in preschool-aged12,13
and elementary school-aged30 children by demonstrating
that, independent of season, weight status, and sex, youth
who spend more time outdoors achieve significantly greater
levels of MVPA than youth who spend little time outdoors.
Furthermore, the observation that youth who spend more
time outdoors are characterized by greater cardiorespiratory
fitness levels and lower sedentary behavior suggests that the
benefits of outdoor activity may extend beyond physical
activity levels. Taken together, these data support the concept
of promoting outdoor time for achieving health benefits in
youth.
Youth spend approximately 8%-15% of their waking
hours in MVPA,5,18 and levels vary based on sex,26 age,26
body weight,1 the built environment,2 and climate.27,31 The
data presented here provide evidence that time spent
outdoors is an additional modifiable determinant of MVPA
levels in youth. Regardless of age, sex, or the time of year,
children who reported spending most or all of the time
outdoors after school accumulated nearly 20 additional
minutes of MVPA per day, 10 of which were achieved during
the after-school period. More importantly, youth who
Schaefer et al
- 2014
Figure 2. MVPA accumulated in the “In School” vs the “After
School” period. Error bars are SEM. *P < .05.
reported spending most of their after-school time outdoors
were approximately three times more likely to achieve
recommended levels of daily physical activity compared
with peers that report spending little time outdoors. This is
an important finding given that only 4%-20% of youth
meet physical activity guidelines for optimal growth and
health.7 These findings support calls for promoting outdoor
activities as a means of increasing MVPA levels in youth.8
Previous work by our group suggests that time spent in
vigorous intensity physical activity is an important
determinant of cardiometabolic health outcomes in youth.14
The data presented here reinforce the notion that reviving
outdoor activities may be an attractive approach for the
promotion of higher intensity physical activity as youth
who reported spending more time outdoors achieved
50% more minutes of vigorous intensity physical activity
compared with youth who spent no time outdoors.9,32
Cardiorespiratory fitness is an important modifiable risk
factor for several cardiometabolic health outcomes in
youth.33,34 Previous studies from this cohort15 and others35
have demonstrated that youth with high cardiorespiratory
fitness are less likely to become overweight or obese over
time. Experimental trials clearly demonstrate that
increasing cardiorespiratory fitness is associated with an
array of cardiometabolic health benefits.36,37 The data
presented here provide evidence that cardiorespiratory
fitness levels are greater among youth who spend more
time outdoors, even after adjusting for established
confounders. These data provide preliminary evidence
that outdoor activities may be a novel modifiable
determinant for enhancing health behaviors beyond
physical activity in children and adolescents.
From a clinical standpoint, the greater levels of MVPA and
lower levels of sedentary behavior among youth reporting
ORIGINAL ARTICLES
spending most of their time outdoors would normally
translate into meaningful differences in cardiometabolic
risk. For example, in previous studies by our group, an
additional 20 minutes of MVPA would translate into a
40% reduced risk of high normal blood pressure and
15% reduced risk of being overweight or obese.14 In the
current study, despite fairly robust differences in MVPA
and sedentary time between youth stratified according to
outdoor time, no differences in overweight status or high
normal blood pressure were observed between the groups.
A modest trend (P = .06) toward a lower waist circumference
was observed with increasing time spent outdoors. These
data support previous work by our group14,32 and others
that physical activity levels are more closely associated with
central obesity than generalized obesity.38,39
The study is strengthened by the use of an objective
measure of physical activity, the rigorous control for several
confounding variables, and the dose-response nature of the
association between outdoor time and health behaviors.
Despite these strengths, some limitations need to be
acknowledged. First, a substantial portion of the study
sample (285/591, 48%) did not provide sufficient data to
assess physical activity adequately or complete the survey
for outdoor time. This does not appear to have influenced
study results, as it has been established that youth who fail
to provide accelerometer data tend to be less active and
more sedentary than youth who provide valid files. Second,
the primary exposure variable is self-reported and is
therefore susceptible to social desirability or other forms
of respondent bias. Related to this, it is unclear whether
the outdoor activity reported by youth was structured or
not; therefore, the policy or experimental implications
remain unclear. Finally, because the data presented are
cross-sectional, the causal nature of this association cannot
be determined.
Future research should include qualitative measures,
addressing the types of activities students are participating
in outdoors, what their environments are composed of,
and why they are choosing to spend time outdoors. Given
that youth spend a substantial amount of time in schools,
increasing outdoor activity should be included in school
wellness policies because these strategies may positively
influence physical activity levels and decrease time spent in
sedentary activities in youth. n
Special thanks to the entire Healthy Hearts Research Team for their
continued dedication to the emerging work.
Submitted for publication Oct 31, 2013; last revision received Apr 2, 2014;
accepted May 14, 2014.
Reprint requests: Jonathan McGavock, PhD, 511-715 McDermot Avenue,
Winnipeg, Manitoba, Canada. E-mail: [email protected]
References
1. Colley RC, Garriguet D, Janssen I, Craig CL, Clarke J, Tremblay MS.
Physical activity of Canadian children and youth: accelerometer results
Outdoor Time Is Associated with Physical Activity, Sedentary Time, and Cardiorespiratory Fitness in Youth
5
THE JOURNAL OF PEDIATRICS
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
6
www.jpeds.com
from the 2007 to 2009 Canadian Health Measures Survey. Health Rep
2011;22:15-23.
Tester JM. The built environment: designing communities to promote
physical activity in children. Pediatrics 2009;123:1591-8.
Marshall SJ, Biddle SJ, Gorely T, Cameron N, Murdey I. Relationships between media use, body fatness and physical activity in children and youth: a meta-analysis. Int J Obes Rel Metab Disord 2004;
28:1238-46.
Burdette HL, Whitaker RC. A national study of neighborhood safety,
outdoor play, television viewing, and obesity in preschool children.
Pediatrics 2005;116:657-62.
Comte M, Hobin E, Majumdar SR, Plotnikoff RC, Ball GD, McGavock J.
Patterns of weekday and weekend physical activity in youth in 2
Canadian provinces. Appl Physiol Nutr Metab 2013;38:115-9.
Vander Ploeg KA, Wu B, McGavock J, Veugelers PJ. Physical activity
among Canadian children on school days and nonschool days. J Phys
Activity Health 2012;9:1138-45.
Garriguet D, Colley RC. Daily patterns of physical activity among
Canadians. Health Rep 2012;23:27-32.
Active Health Kids Canada. Is Active Play Extinct? Active Healthy Kids
Canada Report Card on Physical Activity for Children and Youth.
Toronto, ON; 2012. http://www.activehealthykids.ca/ReportCard/Is%
20Active%20Play%20Extinct.aspx. Accessed May 23, 2014.
Burdette HL, Whitaker RC. Resurrecting free play in young children:
looking beyond fitness and fatness to attention, affiliation, and affect.
Arch Pediatr Adolesc Med 2005;159:46-50.
Clements R. An investigation of the status of outdoor play. Contemp
Issues Early Child 2004;5:68-80.
Yates TaAI. Reporting on the Pan Canadian survey re: Children and
nature. Edmonton: Alberta Recreation and Parks Association; 2010.
Burdette HL, Whitaker RC, Daniels SR. Parental report of outdoor
playtime as a measure of physical activity in preschool-aged children.
Arch Pediatr Adolesc Med 2004;158:353-7.
Cleland V, Crawford D, Baur LA, Hume C, Timperio A, Salmon J.
A prospective examination of children’s time spent outdoors, objectively
measured physical activity and overweight. Int J Obes (Lond) 2008;32:
1685-93.
Hay J, Maximova K, Durksen A, Carson V, Rinaldi RL, Torrance B,
et al. Physical activity intensity and cardiometabolic risk in youth.
Arch Pediatr Adolesc Med 2012;166:1022-9.
McGavock JM, Torrance BD, McGuire KA, Wozny PD, Lewanczuk RZ.
Cardiorespiratory fitness and the risk of overweight in youth: the
Healthy Hearts Longitudinal Study of Cardiometabolic Health. Obesity
(Silver Spring) 2009;17:1802-7.
Storey KE, Forbes LE, Fraser SN, Spence JC, Plotnikoff RC, Raine KD,
et al. Diet quality, nutrition and physical activity among adolescents:
the Web-SPAN (Web-Survey of Physical Activity and Nutrition)
project. Public Health Nutr 2009;12:2009-17.
Storey KE, McCargar LJ. Reliability and validity of Web-SPAN,
a web-based method for assessing weight status, diet and physical activity
in youth. J Human Nutr Dietetics 2012;25:59-68.
Esliger DW, Tremblay MS, Copeland JL, Barnes JD, Huntington GE,
Bassett DR Jr. Physical activity profile of Old Order Amish,
Mennonite, and contemporary children. Med Sci Sports Exerc 2010;
42:296-303.
Esliger DW, Probert A, Connor Gorber S, Bryan S, Laviolette M,
Tremblay MS. Validity of the Actical accelerometer step-count function.
Med Sci Sports Exerc 2007;39:1200-4.
Andersen LB, Harro M, Sardinha LB, Froberg K, Ekelund U, Brage S,
et al. Physical activity and clustered cardiovascular risk in children: a
cross-sectional study (The European Youth Heart Study). Lancet 2006;
368:299-304.
Vol. -, No. 21. Ekelund U, Brage S, Froberg K, Harro M, Anderssen SA, Sardinha LB,
et al. TV viewing and physical activity are independently associated
with metabolic risk in children: the European Youth Heart Study.
PLoS Med 2006;3:e488.
22. Ruiz JR, Labayen I, Ortega FB, Legry V, Moreno LA, Dallongeville J, et al.
Attenuation of the effect of the FTO rs9939609 polymorphism on total
and central body fat by physical activity in adolescents: the HELENA
study. Arch Pediatr Adolesc Med 2010;164:328-33.
23. Puyau MR, Adolph AL, Vohra FA, Zakeri I, Butte NF. Prediction of
activity energy expenditure using accelerometers in children. Med Sci
Sports Exerc 2004;36:1625-31.
24. Leger L, Lambert J, Goulet A, Rowan C, Dinelle Y. Aerobic capacity of 6
to 17-year-old Quebecois–20 meter shuttle run test with 1 minute stages
[in French]. Can J Appl Sport Sci 1984;9:64-9.
25. Cole TJ, Bellizzi MC, Flegal KM, Dietz WH. Establishing a standard
definition for child overweight and obesity worldwide: international
survey. BMJ 2000;320:1240-3.
26. Nader PR, Bradley RH, Houts RM, McRitchie SL, O’Brien M.
Moderate-to-vigorous physical activity from ages 9 to 15 years. JAMA
2008;300:295-305.
27. Carson V, Spence JC, Cutumisu N, Boule N, Edwards J. Seasonal
variation in physical activity among preschool children in a northern
Canadian city. Res Q Exerc Sport 2010;81:392-9.
28. Centers for Disease Control and Prevention. Epi Info. http://wwwn.cdc.
gov/epiinfo/. Accessed May 23, 2014.
29. Grimes DA, Schulz KF. Bias and causal associations in observational
research. Lancet 2002;359:248-52.
30. Cooper AR, Page AS, Wheeler BW, Hillsdon M, Griew P, Jago R.
Patterns of GPS measured time outdoors after school and objective
physical activity in English children: the PEACH project. Int J Behav
Nutr Phys Activity 2010;7:31.
31. Carson V, Spence JC. Seasonal variation in physical activity among
children and adolescents: a review. Pediatr Exerc Sci 2010;22:81-92.
32. Carson V, Rinaldi RL, Torrance B, Maximova K, Ball GD, Majumdar SR,
et al. Vigorous physical activity and longitudinal associations
with cardiometabolic risk factors in youth. Int J Obes (Lond) 2014;38:
16-21.
33. Carnethon MR, Gulati M, Greenland P. Prevalence and cardiovascular
disease correlates of low cardiorespiratory fitness in adolescents and
adults. JAMA 2005;294:2981-8.
34. Ekelund U, Anderssen SA, Froberg K, Sardinha LB, Andersen LB,
Brage S. Independent associations of physical activity and cardiorespiratory fitness with metabolic risk factors in children: the European
youth heart study. Diabetologia 2007;50:1832-40.
35. Kim J, Must A, Fitzmaurice GM, Gillman MW, Chomitz V, Kramer E,
et al. Relationship of physical fitness to prevalence and incidence of
overweight among schoolchildren. Obes Res 2005;13:1246-54.
36. Davis CL, Pollock NK, Waller JL, Allison JD, Dennis BA, Bassali R, et al.
Exercise dose and diabetes risk in overweight and obese children:
a randomized controlled trial. JAMA 2012;308:1103-12.
37. Gutin B, Barbeau P, Owens S, Lemmon CR, Bauman M, Allison J, et al.
Effects of exercise intensity on cardiovascular fitness, total body
composition, and visceral adiposity of obese adolescents. Am J Clin
Nutr 2002;75:818-26.
38. Ekelund U, Luan J, Sherar LB, Esliger DW, Griew P, Cooper A.
Moderate to vigorous physical activity and sedentary time and
cardiometabolic risk factors in children and adolescents. JAMA
2012;307:704-12.
39. Steele RM, van Sluijs EM, Cassidy A, Griffin SJ, Ekelund U. Targeting
sedentary time or moderate- and vigorous-intensity activity: independent relations with adiposity in a population-based sample of 10-y-old
British children. Am J Clin Nutr 2009;90:1185-92.
Schaefer et al