QUANTITATIVE RESEARCH
A cross-cultural comparison of body composition, physical fitness and physical activity between regional samples of Canadian and English children and adolescents 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, PhD2,5
ABSTRACT OBJECTIVES: Cross-cultural comparisons in children’s body composition, health-related fitness and physical activity (PA) are rare due to a shortage of comparable data, but such comparisons may help avert worrying global prevalence in childhood obesity, and declining fitness and PA. METHODS: We drew samples of Canadian and English children (10 years, n=1630, 50% boys) and adolescents (15 years, n=1406, 56% boys) from three separate, regional studies that conducted comparable school-based assessments (2006-2011). For each age-sex group, we assessed betweencountry differences for body composition (mass, height, BMI, waist circumference), cardiorespiratory fitness (CRF; 20 m shuttle run test), strength (handgrip) and self-reported PA. We used multiple regression to investigate whether between-country differences in fitness were explained by body composition and PA. RESULTS: At any age, Canadian boys and girls were taller, heavier, and had greater BMIs and waist circumferences. English children had higher CRF than Canadians, which was explained by differences in body composition and PA. Canadian children were significantly stronger, partly due to greater body size. There were no between-country differences in adolescent boys. Canadian adolescent girls reported more PA than their English counterparts, but neither PA nor body size explained why Canadian adolescent girls had greater CRF or strength. CONCLUSION: Future cross-cultural studies of PA should include indices of growth and fitness to better understand the relationship between intricate differences in PA and health outcomes. KEY WORDS: Physical fitness; physical endurance; muscle strength; body mass index; exercise La traduction du résumé se trouve à la fin de l’article.
O
besity 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 Cardiorespiratory5, 6 and muscular fitness7, 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 Canada10, 11 and England12, 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 Study5). © Canadian Public Health Association, 2014. All rights reserved.
Can J Public Health 2014;105(4):e245-e250.
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 betweencountry differences in fitness. 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:
[email protected] 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.
CANADIAN JOURNAL OF PUBLIC HEALTH • JULY/AUGUST 2014 e245
FITNESS IN CANADIAN AND ENGLISH YOUTH
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±0.6 years; 97% Caucasian) or grade 10 (June–Sept. in 2006, 2007 and 2008; n=966, 59% boys, 15.1±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±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 schools20 (consent: 22%). We included students with baseline data on sex, age, height and body mass (Sept.–Oct. 2011; n=440, 49% boys, 15.3±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 arealevel (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 e246 REVUE CANADIENNE DE SANTÉ PUBLIQUE • VOL. 105, NO. 4
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/m2) 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/m2 and 30 kg/m2, 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° to 0° flexion at the shoulder, and to apply maximal effort between 90° and 0° 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°, 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° and the shoulder flexed at 0°, 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)
-0.4) * -3.0) *** -1.6) *** -0.1) * (-3.3, (-8.9, (-3.8, (-0.3, -1.8 -5.9 -2.7 -0.1 (-1.3, 1.4) (-3.5, 4.0) (-1.9, -1.8) (-0.1, 0.2) -0.6 0.2 -0.1 0.0
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 (1=low, 5=very high PA) and the average denotes the PAQ-score.
Statistical analyses
Bold indicates statistical significance; * p
