A cross-cultural comparison of body composition, physical fitness and physical activity between regional samples of Canadian and English children and adolescents.
Voss, Christine ; Sandercock, Gavin ; Higgins, Joan Wharf 等
Obesity predisposes children to a myriad of cardiometabolic health
complications, including elevated blood pressure, dyslipidemia, and
insulin resistance. (1) In recent decades, Canada and England have
witnessed an accelerated increase in childhood obesity, compared with
other western societies. (2) In both countries, approximately one in
four youth are overweight or obese. (3, 4)
Cardiorespiratory (5, 6) and muscular fitness (7, 8) are positively
and independently related to cardiometabolic health. Higher fitness
levels may attenuate some of the adverse health outcomes associated with
obesity. (9) In light of this, it is of concern that both Canada (10,
11) and England (12, 13) have independently documented secular declines
in health-related fitness among children and youth. While it seems
intuitive that the rise in obesity and decline in fitness might be
causally related, only about 50% of the reduction in child and youth
fitness may be explained by fatness. (14) Further, a concurrent decline
in physical activity (PA) patterns is likely to play a role. Although
population-level data have identified these disconcerting global trends,
direct comparisons across cultures are able to specify common
behavioural characteristics that contribute to this current public
health crisis. International comparisons are rare due to limited
availability of standardized datasets, and are typically restricted to
single, multi-country studies that operate within regional contexts
(e.g., the European Youth Heart Study (5)).
Thus, we conducted cross-sectional analyses to address three
objectives: 1) to assess differences in fitness between regional samples
of Canadian and English children and adolescents; 2) to assess the
influence of body composition/size on between-country differences in
fitness; 3) to assess whether PA explains between-country differences in
fitness.
METHODS
Sample
We drew the analytic sample from three studies: the East of England
Healthy Hearts Study (EoEHHS), Action Schools! BC (AS! BC), and the
Health Promoting Secondary Schools (HPSS) study. All studies took place
in public schools, used similar school-based protocols and validated
field-tests, (15) collected data within the last decade and no more than
five years apart from each other, and were from regions (East of
England, UK; British Columbia, Canada) with a lower childhood obesity
burden compared with their respective national averages. (16, 17)
The EoEHHS is a large (n=8800+) school-based health and fitness
survey of 10-16 yr-olds (overall consent: 98%). (9) We included students
with data on sex, age, height, body mass, and who were in either grades
5-6 on measurement day (May-Sept. 2008; n=1003, 51% boys, 10.7 [+ or -]
0.6 years; 97% Caucasian) or grade 10 (June-Sept. in 2006, 2007 and
2008; n=966, 59% boys, 15.1 [+ or -] 0.4 years; 95% Caucasian). The
sample of the EoEHHS included students from 14 elementary and 12
secondary schools from the counties of Essex and Suffolk. For each
student with complete/valid home postal codes (96%), we obtained Index
of Multiple Deprivation scores (IMD 2007) (18) as a proxy for
socio-economic status (SES). IMD is a composite score of deprivation
indicators at the Lower Super Output Area level. In the EoEHHS sample,
IMD scores were lower (median 10.3, interquartile range (IQR) 6.9-16.9)
than regional (12.4, 7.5-20.3) or national values (17.1, 9.6-30.2),
indicating comparably low area level deprivation in the EoEHHS sample.
AS! BC is an active school model designed to promote PA in
elementary school children, (19) and was evaluated in a controlled trial
(2005-2007; consent: 64%). We included students who attended schools
assigned to the usual practice group, were in grades 5-6, and had valid
data on sex, age, height and body mass (Sept. 2006; n=627, 49% boys,
10.7 [+ or -] 0.6 years, 49% Caucasian). The 14 elementary schools were
located in British Columbia's Lower Mainland (including Metro
Vancouver) and on the southern portion of Vancouver Island. HPSS is a
'Real Community Trial' that assessed the effectiveness of a
whole school model to promote PA and healthy eating in high schools (20)
(consent: 22%). We included students with baseline data on sex, age,
height and body mass (Sept.-Oct. 2011; n=440, 49% boys, 15.3 [+ or -]
0.4 years, 54% Caucasian--ethnicity available for subsample of n=181).
The 10 secondary schools were located in British Columbia's Lower
Mainland (including Metro Vancouver), Southern Interior, and on the
southern portion of Vancouver Island.
As a proxy for SES in the Canadian samples, we obtained area-level
(Census dissemination area) family income (National Household Survey
2011) for students with complete/valid addresses (AS BC!: 68%; HPSS:
93%). Compared with regional ($76,789; IQR: $60,929-$96,567) and
national values ($75,261; $58,180-$95,774), the area-level median family
income was similar in the AS BC! sample ($77,521; $58,826-$89,290), but
greater in the HPSS sample ($81,893; $67,971-$97,715).
For simplicity, we refer to our samples as Canadian or English
children (average age 10 years) and adolescents (average age 15 years).
Protocol
The respective institutional ethics committees approved the
studies. Parental consent and student assent were obtained. Measurements
were conducted at school; students were assessed in small groups during
regular instructional blocks, usually physical education. Trained
researchers performed the standardized field-based measurements.
Body composition
Students wore gym clothing without shoes and had their body mass
(0.1 kg) and height (0.1 cm) measured using standard field equipment
(calibrated according to respective manufacturers' guidelines).
Body mass index (BMI; kg/[m.sup.2]) was categorized into
'normal' (includes underweight), 'overweight' and
'obese' as per International Obesity Task Force criteria
(IOTF), which are age-sex specific cut-offs that correspond to adult
BMIs of 25 kg/[m.sup.2] and 30 kg/[m.sup.2], respectively. (21) Waist
circumference was measured with standard anthropometric tape (0.1 cm) at
the natural narrowing of the waist; the lower of duplicate measurements
was used for analyses.
Cardiorespiratory fitness
Cardiorespiratory fitness (CRF) was measured using the 20 m shuttle
run test, (22) a progressive run to maximal exertion. Students with
health conditions, injuries or illnesses did not participate. Test
details are described elsewhere. (22) In brief, we administered the test
to groups of ~12 students in school gyms, provided uniform instructions
('run for as long as possible', 'reach the line with your
foot in time with the signal', 'if you miss twice in a row,
your test is over'), and acted as 'spotters'. In younger
age groups and where students were unfamiliar with the test, a
researcher acted as 'pacer'. The last completed lap preceding
volitional exhaustion, or when a student failed to maintain the required
running speed twice, was recorded.
Muscular fitness
Muscular fitness was measured by handgrip tests using portable
dynamometers. In the EoEHHS, students were instructed to stand with the
elbow fully extended, to breathe normally, to move their dominant arm
from 180[degrees] to 0[degrees] flexion at the shoulder, and to apply
maximal effort between 90[degrees] and 0[degrees] flexion (TKK5001 GRIP,
Takei Scientific Instruments Co. Ltd, Tokyo, Japan). Students received
verbal encouragement, and we used the best out of two trials (0.1 kg).
In AS! BC, students were instructed to stand with the elbow fully
extended and the shoulder flexed at 45[degrees], and to breathe normally
while applying a maximal isometric effort (Almedic dynamometer, Japan).
Students received verbal encouragement, and the highest value from two
trials was recorded for each arm (0.1 kg). We inferred that the highest
score corresponds to the dominant arm. In HPSS, students were instructed
to stand with their elbow flexed at 90[degrees] and the shoulder flexed
at 0[degrees], and to breathe normally while applying a maximal
isometric effort (Jamar Plus+; Lafayette Instrument Company, Lafayette,
IN). For each arm, the best of three trials was recorded (0.1 kg); we
used the highest score for the dominant arm for analysis. We will refer
to this measure of muscular fitness as strength.
Physical Activity Questionnaire for Children or Adolescents (PAQ-C
or -A)
The Physical Activity Questionnaire for Children (PAQ-C) or
Adolescents (PAQ-A) is a 7-day recall tool that provides general PA
estimates in 8-20 yr-olds during the school year. (23) The 8 (PAQ-A) or
9 (PAQ-C) items capture the frequency of participation in different
activities and sports (activity checklist), effort during physical
education, activity during recess (PAQ-C only), lunch, after school,
evening and at the weekend. Canadians completed the original PAQ-C/A;
(23) the English samples completed a modified activity checklist to
account for contextual differences (e.g., netball replaced cross-country
skiing). (24) Each item is scored on a 5-point scale (l=low, 5=very high
PA) and the average denotes the PAQ-score.
Statistical analyses
We stratified analyses by age and sex due to age-, sex- and age*sex
interaction effects for anthropometric and fitness variables (data not
shown). We assessed between-group differences using independent
two-tailed t-tests (objective 1). To assess the association between
country, anthropometry and fitness (objective 2), we first identified
which indices of body composition/size were correlated with fitness
outcomes (p<0.0S). We then fit multiple linear regression models for
each fitness outcome (dependent variable), using relevant body
size/composition variables, as well as a dummy variable for country
(0=Canada, l=England) as independent variables (Model 1). When
independent variables were collinear (i.e., body mass and BMI), we used
the measure that was most strongly correlated with the dependent
variable (i.e., waist circumference for CRF; height and body mass for
strength; see Table 2). To evaluate whether self-reported PA explained
between-group differences in fitness (objective 3), PAQ-score was added
to the models (Model 2). We did not adjust for ethnicity as it was not a
significant factor in the models. Analyses were performed in Stata/MP
10.1 for Windows (StataCorp LP, TX).
RESULTS
Between-country differences in body composition, fitness and
physical activity
Descriptive characteristics of children and adolescents by sex and
respective between-country differences are reported in Table 1. Children
from England were significantly lighter, shorter and had lower BMI and
waist circumference compared with their Canadian counterparts. Similar
to recent national estimates, (3-4) in both countries approximately 1 in
4 children were overweight or obese. English adolescents were
significantly lighter and shorter than Canadians; BMI and waist
circumference were significantly lower only in English vs. Canadian
girls. Overall, 1 in 5 adolescents was overweight or obese, slightly
lower than national estimates. (3-4)
English children had higher CRF, whereas Canadian children were
significantly stronger. There were no between-country differences in
fitness measures between Canadian and English adolescent boys. Canadian
adolescent girls, however, had greater CRF and strength than English
adolescent girls. PAQ-scores differed only in adolescent girls, with
English girls reporting less PA than Canadian girls. There was a
three-way interaction effect for sex, age group and country
(p<0.001), whereby the magnitude of difference in PAQ-scores between
children and adolescents was greater for English vs. Canadian girls.
Associations between indices of body composition and fitness
The regression models are presented in Table 2 (Model 1). Waist
circumference was inversely related to CRF; adjusting for it reduced
between-country differences in CRF (Table 1). Height and body mass were
positively related to strength; adjusting for them somewhat reduced
between-country differences in strength (Table 1). Associations between
indices of body composition and fitness were generally stronger for
children than adolescents, males than females, and strength than CRF
(25-40% vs. 10-25%).
Associations with physical activity
Table 2 shows regression models with the inclusion of self-reported
PA (Model 2). Self-reported PA and CRF were positively related: for each
additional PAQ-score point (scored between 1-5), students completed
between 5 and 13 shuttles more (Table 2). These models explained an
additional 5% of the variance in CRF in most groups, and as much as 11%
in the adolescent boys. There was no longer an independent country
effect on CRF in children; conversely, it persisted in adolescent girls.
For strength, self-reported PA explained an additional 5% of the
variance in the models in children, and the independent country effect
remained significant. In adolescents, self-reported PA was not
significantly correlated with strength, and the regression models, as
well as the country-effect in adolescent girls, were minimally altered
by its inclusion.
DISCUSSION
In light of the global physical inactivity crisis, (25) it is
crucial that we better understand the relationship between young
people's health (including weight status and fitness) and health
behaviours (such as PA). We contribute to a limited body of knowledge of
cross-cultural differences between children and adolescents from Canada
and England. We found that in children, body composition/size and PA
explained between-country differences in CRF but not strength. We
identified interesting similarities between adolescent boys, and
startling differences between adolescent girls. We discuss our findings
in detail below.
Body composition/size differences between Canadian and English
groups
At all ages, Canadians were significantly taller and heavier than
their English counterparts. We were unable to find reports that compared
body size/composition of children and adolescents who resided in Canada
vs. England and do not know whether this is also true at a population
level. To provide context, we expressed height relative to WHO 2007
reference norms (largely based on US youth in 1977). (26) On average,
all groups of 10-yr-olds were notably taller than norms (all >80th
percentile). Most adolescent groups were also taller than norms, but to
a smaller relative extent (>56th percentile, except English
adolescent girls: 47th percentile). Similar secular increases in height,
particularly in boys and at younger ages, have been described for US
children; because similar increases were not observed in adolescence,
these trends are thought to be attributable to accelerated maturation.
(27) Unfortunately, we had no maturational indicators to investigate its
role in accelerated growth at an early age and/or between-country
differences in height.
Ethnicity differed between English and Canadian cohorts (~95% vs.
~50% Caucasian), but was not a significant correlate of outcomes in the
current analyses. Environmental factors (such as SES) likely affect
growth more than genetic and/or ethnic factors. (28) The potential
mechanistic roles of SES, nutritional status, growth and maturation, as
well as how these relate to health behaviours warrant further study.
Physical activity and body composition explain country differences
in children's fitness
CRF was estimated using a weight-bearing running test (20 m shuttle
run). Typically, children who weigh less perform better in these types
of tests. (29) Indeed, the superior test performance of the English
children was partially explained by their more favourable body
composition (lower waist circumference). However, only body composition
and self-reported PA combined explained all of the between-country
difference.
Questionnaires have the potential to offer contextual insight as to
which types of PA may be important. For example, a more detailed
examination of individual PAQ items (data not shown) identified that
English children--particularly boys--reported to engage more frequently
in aerobic-type activities of intensities great enough to promote CRF,
such as soccer and jogging. In the English context, soccer is a common
and often unstructured activity, meaning that it occurs without adult
instruction, and is frequently observed in parks or in school grounds
during break time. Indeed, 'active play' was recently
highlighted as a key PA domain that requires international action, due
to its troublesome secular decline in many western societies. (30)
A greater level of understanding as to the exact types and doses of
activities that promote CRF, as well as the context in which they occur,
would be beneficial to inform future intervention.
Strength differences in children were likely maturity-dependent
Height and body mass explained up to 40% of the variance in
handgrip strength. However, despite Canadian children being taller and
weighing more than their English counterparts, body size differences did
not explain the between-country difference in strength. We observed
positive correlations between body mass and strength in accordance with
others. (31) However, a more accurate estimate of lean mass might afford
a better understanding of this finding. The association between height
and strength in children, which we also observed in our samples, is an
important phenomenon and one that is thought to explain much of the
differences in strength between similarly aged children. (32) As we had
no measure of maturity, we are unable to speculate as to how it
contributes to between-country differences in strength per se, or its
potential mediating effect via greater height.
We generally found no association between strength and
self-reported PA (as we did for fitness). This is unsurprising given
that the PAQ is not designed to measure specific resistance exercise
known to improve muscular strength in this population. (33) As strength
is related to cardiometabolic health in youth, (7,8) further study of
determinants of strength is warranted and might include measures of
muscle mass, strength/power, participation in resistance-type activities
and maturity level.
Why were Canadian adolescent girls fitter and stronger?
In contrast to the likeness between Canadian and English adolescent
boys, Canadian girls were fitter, stronger and reported higher levels of
PA than English adolescent girls. Although PA typically declines as
children age, (24) the magnitude of this expected difference was
significantly greater in English than in Canadian girls. Nevertheless,
the greater levels of PA in Canadian adolescent girls did not explain
the between-country differences in fitness or strength. The PAQ is
unlikely to sensitively capture specific components of PA (e.g.,
intensity and frequency) that could explain differences in fitness in
this age group. Identifying factors that attenuate the age-dependent
decline in PA is important for designing effective PA promotion
strategies. Qualitative approaches might help to drill down to determine
whether factors such as social desirability of PA behaviours play a
role, specifically in adolescent girls.
It is notable that Canadian adolescent girls had less desirable
indices of body composition than English adolescent girls, yet they
performed better in the shuttle run. There is debate over the role of
school-based fitness testing and its potential negative effect on
emotional well-being and motivation for PA. (34) Our data did not
support the notion that students with excess body fat (greater waist
circumferences) were disadvantaged per se in the shuttle run. Adequate
fitness levels can attenuate adverse health consequences associated with
obesity, (9) and maintaining fitness should be a target for health
promotion in youth.
Limitations
The school-based studies were not regionally representative but
were volunteer samples, a common strategy to sample students from all
SES relative to a study area. (19) We did not have access to
internationally comparable indicators of individual- or area-level SES
and were thus unable to account for its potential mediating role. This
is an important consideration for future cross-cultural studies aiming
to elucidate mechanisms which may explain disparities in health outcomes
and/or health behaviours. Consent rates differed between studies, which
could have introduced selection bias; for example, students enjoying PA
may have been more likely to participate. However, the ranges we noted
in our objective outcomes, as well as the between-country differences,
do not support the hypothesis of systematic bias (i.e., fitter Canadians
would also have lower BMI). The 20 m shuttle run test is a valid tool,
(15) but test familiarization and day-to-day performance variation may
influence individual results. However, we expect this variability would
be common to both countries and would therefore not influence our
findings. Handgrip is a valid field-test to estimate muscular fitness in
youth; (15) dynamometer and protocol may, however, affect scores. (35)
The current studies adopted different protocols and dynamometers that
should have theoretically advantaged the English groups (extended elbow,
Takei dynamometer). (35) However, the English groups had lower scores
than the Canadians; thus, we are confident that Canadians were stronger
but cannot be certain of the true magnitude of the difference. Last, PA
was assessed by questionnaire and although recall error is a
well-documented problem in youth, (36) the PAQ has construct validity.
(24) The cross-sectional design of this analysis does not enable us to
infer causality.
CONCLUSION
Our findings in two developed nations lend credence to the notion
of a global 'pandemic of physical inactivity' (25)--with a
reach that extends to encompass children and youth. Future international
collaborative efforts, such as the recent global matrix of physical
activity 'grades' across countries, (30) should consider
extending standardized monitoring to include indices of growth and
fitness, and place an emphasis on identifying underlying cross-cultural
differences in the intricacies of PA behaviours (such as unstructured PA
or active play).
Acknowledgements: For concept, design and implementation of
respective studies, we acknowledge Bryna Kopelow, Jennifer Fenton (both
AS! BC), Sandra Gibbons, Ryan Rhodes, Lauren Sulz, Sandy Courtnall, Dona
Tomlin, Douglas Race and Vina Tan (all HPSS), Daniel Cohen, Ayo Ogunleye
(both EoEHHS) and many more research assistants and students for their
invaluable and multi-faceted contributions to the respective study
teams. We are indebted to school administrators, teachers, students and
their parents who participated in the studies. AS! BC was funded by the
Canadian Institutes of Health Research (OCO-74248), Heart and Stroke
Foundation (BC Heart PG05-0327), 2010 Legacies Now and the Bc Ministry
of Health. The HPSS study was funded by the Canadian Cancer Society
Prevention Initiative (# 21044) and the Canadian Institutes of Health
Research (CBO-109634). The EoEHHS was funded by the University of Essex
Research Development Fund. CV was supported by a Government of Canada
Fellowship.
Conflict of Interest: None to declare.
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Received: February 16, 2014
Accepted: June 19, 2014
Christine Voss, PhD, [1,2] Gavin Sandercock, PhD, [3] Joan Wharf
Higgins, PhD, [4] Heather Macdonald, PhD, [1,2] Lindsay Nettlefold, PhD,
[2] Patti-Jean Naylor, PhD, [4] Heather McKay, PhD [2,5]
Author Affiliations
[1.] Department of Orthopaedics, University of British Columbia,
Vancouver, BC
[2.] Centre for Hip Health and Mobility, Robert H.N. Ho Research
Centre, Vancouver, BC
[3.] School of Biological Sciences, University of Essex, Wivenhoe
Park, Colchester, United Kingdom
[4.] School of Exercise Science, Physical and Health Education,
University of Victoria, Victoria, BC
[5.] Departments of Orthopaedics and Family Practice, University of
British Columbia, Vancouver, BC
Correspondence: Christine Voss, Centre for Hip Health and Mobility,
Robert H.N. Ho Research Centre, 684C-2635 Laurel Street, Vancouver, BC
V5Z 1M9, E-mail: christine.voss@hiphealth.ca
Table 1. Sample descriptive statistics
(mean [+ or -] SD (n)) and between-country
differences (95% Cl ([dagger])), stratified
by age group and sex
Males
England
Children
Age (yrs) 10.7 [+ or -] 0.6 (510)
Body mass (kg) 58.6 [+ or -] 9.0 (510)
Height (cm) 143.4 [+ or -] 7.5 (510)
BMI (kg/[m.sup.2]) 18.6 [+ or -] 3.1 (510)
% overweight/obese 20.2%/5.3%
([double dagger])
Waist (cm) 64.7 [+ or -] 8.8 (485)
Shuttles (laps) 40.0 [+ or -] 20.6 (482)
Handgrip (kg) 16.8 [+ or -] 3.8 (501)
PAQ-score ([section]) 3.28 [+ or -] 0.7 (315)
Adolescents
Age (yrs) 15.1 [+ or -] 0.4 (567)
Body mass (kg) 61.6 [+ or -] 12.0 (567)
Height (cm) 170.2 [+ or -] 8.0 (567)
BMI (kg/[m.sup.2]) 21.2 [+ or -] 3.4 (567)
% overweight/obese 15.2%/4.1%
([double dagger])
Waist (cm) 73.8 [+ or -] 8.8 (554)
Shuttles (laps) 65.4 [+ or -] 26.7 (522)
Handgrip (kg) 36.1 [+ or -] 8.1 (521)
PAQ-score ([section]) 2.88 [+ or -] 0.7 (552)
Males
Canada
Children
Age (yrs) 10.8 [+ or -] 0.6 (310)
Body mass (kg) 41.9 [+ or -] 11.5 (310)
Height (cm) 145.9 [+ or -] 7.9 (310)
BMI (kg/[m.sup.2]) 19.5 [+ or -] 4.0 (310)
% overweight/obese 25.2%/8.4%
([double dagger])
Waist (cm) 67.6 [+ or -] 9.6 (309)
Shuttles (laps) 34.8 [+ or -] 17.1 (260)
Handgrip (kg) 21.5 [+ or -] 4.8 (264)
PAQ-score ([section]) 3.26 [+ or -] 0.6 (303)
Adolescents
Age (yrs) 15.3 [+ or -] 0.4 (216)
Body mass (kg) 65.0 [+ or -] 11.8 (216)
Height (cm) 173.5 [+ or -] 7.2 (216)
BMI (kg/[m.sup.2]) 21.6 [+ or -] 3.4 (216)
% overweight/obese 15.7%/ 4.6%
([double dagger])
Waist (cm) 73.8 [+ or -] 8.3 (216)
Shuttles (laps) 65.2 [+ or -] 21.7 (207)
Handgrip (kg) 36.2 [+ or -] 7.7 (82)
PAQ-score ([section]) 2.85 [+ or -] 0.5 (82)
Males
Difference
(95% Cl ([dagger]))
Children
Age (yrs) -0.1 (-0.1, 0.0)
Body mass (kg) -3.3 (-4.8,-1.8)# ***
Height (cm) -2.4 (-3.5,-1.4)# ***
BMI (kg/[m.sup.2]) -0.9 (-1.4,-0.3)# **
% overweight/obese
([double dagger])
Waist (cm) -3.2 (-4.5,-1.8)# ***
Shuttles (laps) 5.2 (2.5, 8.0)# ***
Handgrip (kg) -4.6 (-5.3,-3.9)# ***
PAQ-score ([section]) 0.0 (-0.1, 0.1)
Adolescents
Age (yrs) -0.3 (-0.3, -0.2)# ***
Body mass (kg) -3.4 (-5.3, -1.6)# ***
Height (cm) -3.3 (-4.5,-2.1)# ***
BMI (kg/[m.sup.2]) -0.4 (-0.9, 0.2)
% overweight/obese
([double dagger])
Waist (cm) -0.6 (-1.3,1.4)
Shuttles (laps) 0.2 (-3.5, 4.0)
Handgrip (kg) -0.1 (-1.9,-1.8)
PAQ-score ([section]) 0.0 (-0.1, 0.2)
Females
England
Children
Age (yrs) 10.7 [+ or -] 0.6 (493)
Body mass (kg) 39.1 [+ or -] 9.0 (493)
Height (cm) 143.9 [+ or -] 7.7 (493)
BMI (kg/[m.sup.2]) 18.7 [+ or -] 3.1 (493)
% overweight/obese 20.5%/4.7%
([double dagger])
Waist (cm) 63.2 [+ or -] 8.0 (473)
Shuttles (laps) 30.3[+ or -] 15.0 (488)
Handgrip (kg) 15.9 [+ or -] 2.8 (486)
PAQ-score ([section]) 3.08 [+ or -] 0.6 (304)
Adolescents
Age (yrs) 15.1 [+ or -] 0.4 (399)
Body mass (kg) 56.3 [+ or -] 9.0 (399)
Height (cm) 161.2 [+ or -] 6.4 (399)
BMI (kg/[m.sup.2]) 21.6 [+ or -] 3.1 (399)
% overweight/obese 16.0%/2.0%
([double dagger])
Waist (cm) 69.7 [+ or -] 7.8 (394)
Shuttles (laps) 36.6 [+ or -] 17.3 (367)
Handgrip (kg) 26.3 [+ or -] 4.9 (351)
PAQ-score ([section]) 2.48 [+ or -] 0.6 (391)
Females
Canada
Children
Age (yrs) 10.7 [+ or -] 0.6 (317)
Body mass (kg) 40.7 [+ or -] 10.0 (317)
Height (cm) 146.2 [+ or -] 8.1 (317)
BMI (kg/[m.sup.2]) 18.9 [+ or -] 3.4 (317)
% overweight/obese 19.6%/6.0%
([double dagger])
Waist (cm) 65.0 [+ or -] 8.6 (317)
Shuttles (laps) 27.3 [+ or -] 13.4 (354)
Handgrip (kg) 19.2 [+ or -] 4.7 (357)
PAQ-score ([section]) 2.99 [+ or -] 0.6 (305)
Adolescents
Age (yrs) 15.3 [+ or -] 0.3 (224)
Body mass (kg) 59.5 [+ or -] 11.8 (224)
Height (cm) 163.2 [+ or -] 6.2 (224)
BMI (kg/[m.sup.2]) 22.3 [+ or -] 4.2 (224)
% overweight/obese 20.1%/5.4%
([double dagger])
Waist (cm) 71.5 [+ or -] 9.2 (224)
Shuttles (laps) 43.5 [+ or -] 17.8 (217)
Handgrip (kg) 29.0 [+ or -] 5.1 (99)
PAQ-score ([section]) 2.61 [+ or -] 0.5 (99)
Females
Difference
(95% Cl ([dagger]))
Children
Age (yrs) 0.1 (0.0, 0.1)
Body mass (kg) -1.6 (-3.0, -0.3)# *
Height (cm) -2.3 (-3.4,-1.2)# ***
BMI (kg/[m.sup.2]) -0.1 (-0.6, -0.3)
% overweight/obese
([double dagger])
Waist (cm) -1.8 (-3.0, -0.6)# **
Shuttles (laps) 3.1 (0.9, 5.2)# **
Handgrip (kg) -3.4 (-4.1, -2.7)# ***
PAQ-score ([section]) 0.1 (-0.0, 0.2)
Adolescents
Age (yrs) -0.2 (-0.3, -0.2)# ***
Body mass (kg) -3.2 (-5.0,-1.4)# ***
Height (cm) -2.0 (-3.0, -0.9)# ***
BMI (kg/[m.sup.2]) -0.7 (-1.3, -0.1)# *
% overweight/obese
([double dagger])
Waist (cm) -1.8 (-3.3,-0.4)# *
Shuttles (laps) -5.9 (-8.9, -3.0)# ***
Handgrip (kg) -2.7 (-3.8, -1.6)# ***
PAQ-score ([section]) -0.1 (-0.3,-0.1)# *
Bold indicates statistical significance; * p<0.05, ** p<0.01,
*** p<0.001. Note: all comparisons are unadjusted for multiple
comparisons,
([dagger]) 95% Cl--upper and lower limit 95% confidence intervals;
([double dagger]) BMI weight classification as per International
Obesity Task Force criteria. (21)
([section]) PAQ-score--Physical Activity Questionnaire score:
mean score of 8-9 questionnaire items, scored between 1 (no/low PA)
and 5 (very high PA).
Table 2. Multiple regression analyses for indices of fitness,
stratified by age group and sex
Males
Model 1
[beta] (95% CI ([double
([dagger]) dagger])
Children (10 yrs) ([section])
DV: Shuttle run (laps)
Country (UK; ref: Canada) 3.22# (0.59, 5.86)# *
Waist (cm) -1.03# (-1.17, -0.89)# ***
PAQ-score ([parallel])
[r.sup.2] (n) 0.242 (718) ***
DV: Handgrip (kg)
Country (UK; ref: Canada) -3.95# (-4.51, -3.40)# ***
Height (cm) 0.18# (0.13, 0.22)# ***
Body mass (kg) 0.08# (0.04, 0.12)# ***
PAQ-score ([parallel])
[r.sup.2] (n) 0.398 (765) ***
Adolescents (15 yrs)
([section])
DV: Shuttle run (laps)
Country (UK; ref: Canada) 1.01 (-4.73, 6.84)
Waist (cm) -0.98# (-1.21, -0.74)# ***
Handgrip (kg) 1.07# (0.81, 1.32)# ***
PAQ-score ([parallel])
[r.sup.2] (n) 0.171 (548) ***
DV: Handgrip (kg)
Country (UK; ref: Canada) 1.58# (0.02, 3.13)# *
Height (cm) 0.20# (0.11, 0.28)# ***
Body mass (kg) 0.28# (0.23, 0.34)# ***
Shuttles (laps) 0.09# (0.07, 0.11)# ***
PAQ-score ([parallel])
[r.sup.2] (n) 0.376 (556) ***
Males
Model 2
[beta] (95% CI ([double
([dagger]) dagger])
Children (10 yrs) ([section])
DV: Shuttle run (laps)
Country (UK; ref: Canada) 2.57 (-0.12, 5.26)
Waist (cm) -0.84# (-0.99, -0.70)# ***
PAQ-score ([parallel]) 7.39# (5.33, 9.46)# ***
[r.sup.2] (n) 0.291 (534) ***
DV: Handgrip (kg)
Country (UK; ref: Canada) -4.14# (-4.78, -3.53)# ***
Height (cm) 0.18# (0.13, 0.24)# ***
Body mass (kg) 0.10# (0.06, 0.14)# ***
PAQ-score ([parallel]) 0.87# (0.41, 1.32)# ***
[r.sup.2] (n) 0.451 (566) ***
Adolescents (15 yrs)
([section])
DV: Shuttle run (laps)
Country (UK; ref: Canada) 0.83 (-4.53, 6.18)
Waist (cm) -0.95# (-1.16, -0.73)# ***
Handgrip (kg) 0.99 (0.75, 1.23) ***
PAQ-score ([parallel]) 12.97# (10.29, 15.66)# ***
[r.sup.2] (n) 0.288 (541) ***
DV: Handgrip (kg)
Country (UK; ref: Canada) 1.56 (-0.01, 3.13) ([dagger])
Height (cm) 0.19# (0.10, 0.27)# ***
Body mass (kg) 0.29# (0.23, 0.35)# ***
Shuttles (laps) 0.09# (0.07, 0.12)# ***
PAQ-score ([parallel]) -0.08 (-0.91, 0.76)
[r.sup.2] (n) 0.378 (548) ***
Females
Model 1
[beta] (95% CI ([double
([dagger]) dagger])
Children (10 yrs) ([section])
DV: Shuttle run (laps)
Country (UK; ref: Canada) 2.55# (0.49, 4.60) *
Waist (cm) -0.66# (-0.78, -0.54)# ***
PAQ-score ([parallel])
[r.sup.2] (n) 0.151 (722) ***
DV: Handgrip (kg)
Country (UK; ref: Canada) -2.81# (-3.34, -2.28)# ***
Height (cm) 0.21# (0.16, 0.25)# ***
Body mass (kg) 0.09# (0.05, 0.13)# ***
PAQ-score ([parallel])
[r.sup.2] (n) 0.395 (743) ***
Adolescents (15 yrs)
([section])
DV: Shuttle run (laps)
Country (UK; ref: Canada) -5.10# (-9.08, -1.11)# *
Waist (cm) -0.65# (-0.86, -0.43)# ***
Handgrip (kg) 0.55# (0.21, 0.88)# ***
PAQ-score ([parallel])
[r.sup.2] (n) 0.098(426) ***
DV: Handgrip (kg)
Country (UK; ref: Canada) -1.83# (-2.86, -0.80)# **
Height (cm) 0.14# (0.07, 0.21)# ***
Body mass (kg) 0.18# (0.13, 0.23)# ***
Shuttles (laps) 0.05# (0.02, 0.07)# ***
PAQ-score ([parallel])
[r.sup.2] (n) 0.244 (429) ***
Females
Model 2
[beta] (95% CI ([double
([dagger]) dagger])
Children (10 yrs) ([section])
DV: Shuttle run (laps)
Country (UK; ref: Canada) 1.25# (-0.90, 3.39)#
Waist (cm) -0.61# (-0.74, -0.48)# ***
PAQ-score ([parallel]) 5.31# (3.49, 7.12)# ***
[r.sup.2] (n) 0.201 (534) ***
DV: Handgrip (kg)
Country (UK; ref: Canada) -3.14# (-3.75, -2.52)# ***
Height (cm) 0.21# (0.16, 0.27)# ***
Body mass (kg) 0.10# (0.05, 0.14)# ***
PAQ-score ([parallel]) 0.57# (0.05, 1.08)# *
[r.sup.2] (n) 0.416 (545) ***
Adolescents (15 yrs)
([section])
DV: Shuttle run (laps)
Country (UK; ref: Canada) -4.60# (-8.49, -0.72)# *
Waist (cm) -0.63# (-0.84, -0.42)# ***
Handgrip (kg) 0.39# (0.05, 0.72)# *
PAQ-score ([parallel]) 7.33# (4.67, 9.98)# ***
[r.sup.2] (n) 0.156 (419) ***
DV: Handgrip (kg)
Country (UK; ref: Canada) -1.77# (-2.80, -0.74)# **
Height (cm) 0.15# (0.07, 0.22)# ***
Body mass (kg) 0.17# (0.12, 0.22)# ***
Shuttles (laps) 0.04# (0.01, 0.06)# **
PAQ-score ([parallel]) 0.79 (0.07, 1.52) *
[r.sup.2] (n) 0.254 (422) ***
Model 1--Association between country and relevant indices of body
composition/size on fitness outcomes; Model 2--Model 1 plus
inclusion of PAQ-score.
Bold regression coefficients are significant; * p<0.05, ** p<0.01,
*** p<0.001. Note: all models are unadjusted for multiple
comparisons. ([dagger]) = unstandardized beta coefficient;
([double dagger]) 95% CI--upper and lower limit 95% confidence
intervals; ([section]) in children, mean age [+ or -] SD was
10.7 [+ or -] 0.6 in males and 10.7 [+ or -] 0.6 in females; in
adolescents, it was 15.2 [+ or -] 0.4 in males and 15.1 [+ or -]
0.4 in females; ([parallel]) PAQ-score--Physical Activity
Questionnaire score: mean score of 8-9 questionnaire items,
scored between 1 (no/low PA) and 5 (very high PA).
Note: Regression coefficients are indicated with #.
