Encouraging Children to Join Skill Based Physical Activities

ABSTRACT

Objective: The objective of the study was to encourage young primary 4/ 5 school children to participate in skill based physical activity like dance which has better health benefits then the regular physical education sessions.

Methods: An epidemiological cohort study was conducted in randomly selected three schools in Glasgow. 95 children participated out of which 64 underwent 16 weeks of dance training as an additional physical education session in schools by a trained dance professional. Control group (N=31) children attended the regular physical education session of the school. For both the groups measurements were taken at baseline, post 8 weeks and post 16 weeks of the intervention. The aerobic fitness and body fat percentage were the major criteria to assess the effectiveness of the study. Aerobic fitness was measured by 20 m shuttle run test and body fat was assesses by Tanita body composition analyser.

Results: A significant improvement in aerobic capacity was reported in the intervention group with mean -1.71 ± SD 1.77; p value < 0.001, 95% confidence interval for mean difference was in the range of (-2.34, -1.08). A reduction in body fat was also recorded with mean difference of 2.57 ± SD 18.04; p value= 0.35, 95% confidence interval for mean difference (-2.91, 8.06).

Conclusion: The 16 week dance intervention has enhanced the aerobic fitness in children. The study suggests that a well planned entertaining skill based PE session can have positive influence upon increasing physical activity levels in young children.

INTRODUCTION

Physical inactivity is estimated to cause 2 million deaths worldwide annually. Furthermore it contributes largely to medical costs [1]. Engaging in regular physical activity is an essential element in preventing chronic diseases [2]. It is presupposed that improved physical activity in childhood can reduce the health risks associated with inactivity and benefit health both during childhood and adulthood [3]. However in recent years the inflating physical inactivity in children around the world has gathered considerable attention [4, 5, 6].

The increasing prevalence of overweight and obesity in children has been attributed in part, to decrease in physical activity. The imbalance in energy intake and energy expenditure is a major root for epidemic of child obesity [7]. A large proportion of children in Scotland are insufficiently active in order to gain subsequent health benefits, hence promotion of health enhancing physical activity to children has become a public health priority. Guidelines for Appropriate Physical Activity for Elementary School Children states that children should accumulate at least sixty minutes of moderate to vigorous physical activity (MVPA) in a day [8]. To a certain limit, a linear dose-response relationship between physical activity and health can be seen [9].

Researches suggest that habitual physical activity levels decreases over the lifespan, hence children are more active than adolescents and further more than adults. Hence it can be proposed that children who do not develop patterns of regular physical activity are at risk of being sedentary adults. The adequate fitness in childhood is likely to carry beneficial biological and behavioural effects into adulthood. Physically active children are more likely to become physically active adults [10].

The declined physical activity in young children today is widely noticeable; computer games and television shows are attracting child’s attention and are preferred over play [11]. Children from sedentary parents are found to be comparatively more inactive then their other counter parts.

The triad between physical inactivity, obesity and unhealthiness can be presumed seeing the correlation between the three. Obesity can be relate as a unforeseen trait in a number of chronic diseases and conditions in early and later life like cardiovascular and respiratory problems, insulin resistance (type II diabetes), osteoarthritis, endocrine and metabolic disorders, psychological imbalance etc [12,13].

While evidence proves that physical activity in children improves the bone strength, benefits cardiovascular system, improve glycemic control, improves metabolism, reduce the risk of specific cancers, induce positive state of well-being like self- esteem, self-efficacy, and positive mood states [14,15,16,17,18]. Studies report positive effect of exercise training on cognition in elementary school children [19]. Churchill et al., (2002) suggest improvements in cognition due to exercise is mainly on executive function [20]. The inclusion of a healthy dose of vigorous physical activity in schools as a part of the Educational curriculum can improve the overall development of the child.

The school has emerged as a critical setting for promoting health enhancing physical activity in children [21, 22, 23, 24]. School is a universal place where every child around the world spends most of his or her time, hence is a key factor in improving physical activity in children. Studies reviewing the effect of school based interventions propose an improved level of health-related knowledge and fitness in children. But in terms of obesity prevention not much effect has been detected. However, some measure of obesity has found to be downsized. Physical education in schools is not sufficient enough to provide notable health benefits. It appears that when children are given free choice, many of them seem to be less active. In order to get the health related effects it is important to offer skill based physical education sessions like dance, football, rugby etc where children can engage in moderate-to-vigorous physical activity. There are evidence that proves the effect of moderate- vigorous physical activity (MVPA) in weight stability and cardiovascular health [25].

In order to improve physical activity trends in Scottish schools, a school based intervention involving primary school children was developed. The intervention was designed to encourage children to participate in physical activity like dance which is more likely to be welcomed by children of younger age group and to continue it throughout their school career. To upgrade aerobic fitness and to downgrade the fat percentile in children were among the components of the study plan.

METHODOLOGY

The intervention “Dance Yourself Fit” focuses on improving the physical activity trends in primary 4-5 school children. Since it has been presupposed that notion of play starts declining by this age. By choosing dance as the mode of exercise, the intervention aims toward enhancing the skill based physical activity in schools along with an increase in the number of physical education (PE) sessions per week.

Study design and sampling

The Glasgow City Council has randomly selected three primary schools from the same socioeconomic area for the study. 95 healthy 8-9 years old volunteers including 54 girls and 41 boys participated from primary 4-5 classes. The mean weight and height of the participants before the initiation of the study was 30.09 kg with 95% CI (28.428- 131.769) and 132.24 cm with 95% CI (130.75- 133.73) respectively.

Each school was visited prior to the start of the study to ensure all potential volunteers, teachers and parents are fully aware of the aims of the study. The method of monitoring and assessment was explained to the students. Adjustment was made by the school to include two physical education sessions per week in their timetable. A qualified dance professional was recruited as a coach to train the students with dance.

Normal and healthy is defined as those without any medical condition which can hamper their ability to participate in aerobic exercise. Physical activity and medical questionnaire were given to the students and those considered unsuitable by the test results were excluded from the participation. Children were instructed to cease exercise if they feel any discomfort.

Subjects

Intervention group consists of 64 students from all the three primary schools. Control group comprise of 31 students, from one of the three randomly selected intervention schools. Children in the control group follow their normal PE sessions and physical activity and they are monitored followed by the intervention group every time the assessment is taken. The flow chart (figure: 1) represents the availability of children for measurements at each level.

Consent for participation in the study was taken from the parents/guardians and the participants.

Ethical approval of the study was obtained from the ethical community of the University of Glasgow.

Exercise Plan

Dance sessions were planned for 16 weeks, twice every week for a period of an hour/session. As per Serbescu C et. al two extra sessions of physical education per week were sufficient to obtain improvement in fitness level of the children [26]. Each dance session has a structured format commencing with 5 minutes of warm up followed by 45 minutes of moderate to high intensity dance moves with target intensity reaching up to 65-80% of maximum heart rate and a short cool down period.

Measures

All the measurements were taken at the baseline, intermediate (i.e. at the end of 8th week) and final levels by the well trained research staff.

Comparison between the three levels was done for both the groups to judge the effectiveness of the intervention. In the intervention group, 44 children were present for baseline and final measurements, 41 for baseline and intermediate and 31 for intermediate and final measurements.

Heart rate: Exercise intensity was monitored by ‘Polar Heart Rate Monitor’. Heart rate monitoring has been used successfully as a means of estimating the stress placed on the cardiopulmonary system and provides an indication of the intensity, duration and frequency of activity [27]. Heart rate monitoring belts were made to worn during the dance sessions. Data was stored in ‘Polar’ performance software and analysed.

Height: A portable stadiometer was used to measure height in centimeters (cm) to the nearest 0.1 cm.

Weight: Tanita body composition analyser was used to measure weight in kilograms (kg) to the nearest 0.1 kg.

Both weight and height were measured in light clothing like track pants or shorts with shoe off.

Body Fat Percentage: Bioelectrical impedence, a non invasive validated procedure used for measuring body fat [28]. Tanita body composition analyser was used for the same. Houtkooper LB et al suggest that bioelectric impedence is a better test specifically for grading average adiposity in groups [29].

Cardio-respiratory Fitness: The “multistage 20-meter shuttle run” (MST) / bleep test / beep test was used to assess the maximal aerobic capacity (VO2max). Since (VO2max) is considered as a gold standard to assess cardiovascular fitness and MST is a validated test to measure the maximal oxygen uptake [30]. Maximum oxygen carrying capacity (VO2max) and aerobic fitness are directly proportional to each other; a higher (VO2max) value indicates a better cardio respiratory fitness. The test protocol consists of 23 levels. Each level last for 1 minute and comprise of a series of laps that were ran back to forth between two lines set 20 metres apart, with a starting speed of 8.5 km/hr and increases by 0.5 km/hr at each level using a pre-recorded audio tape. A single beep indicates end of a level and three beeps indicate start of the next level. Students can walk, jog or run keeping in time with the beeps until they cannot keep in time with the speed set by the tape which is student’s maximal effort. MST table was used to assess the (VO2max) values [31, 32].

Statistical Analysis

Paired t test was used to compare the aerobic fitness (MST score), weight, height and body fat percentile values at baseline, intermediate and final level of both the control and intervention group. Descriptive data are mean ± SD and statistical significance was analysed at p< 0.05. All analyses were performed using Minitab 15.

RESULTS

Completed baseline, intermediate and final data were collected from students at the beginning, post 8 weeks and post 16 weeks respectively. Out of 95, 10 students were not present on the day of baseline measurements, 13 for the intermediate and 34 for the final measurements. Height, weight, age, sex, body fat percentage, and MST score were calculated for each child. Some students had incomplete data because of absence on more than 1 day of measurement. These data were excluded from the analysis.

Body Fat Percentage

Final results showed an overall reduction in fat percentage. At baseline, relative to the control group, children in the intervention group had significantly higher body fat percentage (4.17% higher). Comparing the baseline and final data of body fat percentage in the intervention group, a reduction in fat mass with mean of 2.57 ± SD 18.04, p value 0.35 was observed. While baseline and intermediate showed a mean difference of 3.26 ± SD 19.85, p value 0.30. An increase in fat percentile was reported from intermediate to the final results with mean -1.34 ± SD 4.75, p value 0.126. The readings of mean and SD of body fat percentage at all the three levels is given in table1.

Aerobic Fitness

An improvement in the Multistage Shuttle Run Test (MST) score has been observed in both the groups. At baseline, relative to the control group, children in the intervention group had significantly lower aerobic capacity, but by the end of the study intervention group showed better improvement in the aerobic capacity compare to the control group. A significant improvement with p value < 0.001 has been notified in the intervention group with a mean -1.71 ± SD 1.77, 95% confidence interval for mean difference was in the range of (-2.34, -1.08). The readings of mean and SD of body MST score is given in table 2.

Heart rate

Heart rate was monitored in all the dance sessions for the intervention group as well as the control group during their regular physical activity sessions. Comparing the results of boys from the intervention and control group a higher value of resting heart rate (HR), maximum heart rate (MHR) and average heart rate ( AHR) was reported in the pupil of the intervention group ( 126 bpm, 166 bpm, 132 bpm respectively). For the detailed report of the heart rate during the dance session refer figure: 2.

Heart rate monitoring of one of the boy from the control group during the regular PE session showed following results. HR: 87 bpm, MHR: 157 bpm, AHR: 106 bpm . Refer figure: 3 for detailed picture of the heart rate during a regular physical activity session.

The heart rate monitor of a girl from the intervention group showed following results. HR: 136 bpm, MHR: 193 bpm and AHR: 156 bpm. A complete range of heart rate during the dance session is given in figure: 4.

Gender Difference

In the intervention group at the baseline girls had significantly higher estimated body fat percentage (about 4.2 % higher) than boys. This difference in body fat % at the end of intervention went down to 2.24 %. Girls reported significant improvement in the aerobic capacity during the intervention period. Table 3 describes the individual readings of mean and SD of body fat percentage, MST and weight of boys and girls in the intervention group at baseline and final levels. Girls touched approximately 190 bpm of heart rate during the dance session which is much better then the boys MHR range during the dance session.

DISCUSSION

The unhealthy life style is the major risk factor for many preventive chronic diseases. Therefore the elevating sedentary behaviour in children has become a public health concern around the globe. It has been documented that improved level of exercise capacity in children confers protection against many chronic diseases with underlying risk factors like obesity [33]. Number of studies has confirmed the significance of school based intervention in promoting physical activity in children [21, 22, 23, 24].

Most of these studies involve multiple component procedure like physical activity, time spent in physical activity, dietary intake, class room education, parent’s involvement etc [34, 35, 36].Though, these studies were designed intensively and most of them had a long follow up period but still were not able to discover the precise factor (physical activity or dietary habits) that has the prime potential in improving the health status of the children. Further more most of these studies are self reporting and hence the results of such interventions can not be considered as significant. In the present study we focused on a novel school-based approach to boost the involvement of children in physical activity which can have health benefits as well as have rejoicing effect on children so that an attempt is made to gain their interest in being active. Our aim was to make the sessions so exciting that children do not find them stereotyped.

Health benefits of the intervention

Physical activity

The intervention “Dance Yourself Fit” was designed to test the hypothesis that children who participated in 16 weeks of dance sessions conducted by the professional coach would report significant improvement in aerobic capacity and reduction in body fat in contrast to a control group who engaged in the regular PE sessions. In accordance with the hypothesis, the results revealed that scores of MST for children in the intervention group increased significantly following 16 weeks of training. The findings indicate reduced body fat compare to the control group at the end of the intervention as per the bioelectric impedence measurements. In this respect, the study support previously conducted study on physical activity and fitness in elementary school children (Sallis JF, McKenzie TL et al., 1997) [24] and research by Dwyer T et al in South Australia on the effect of daily physical activity in primary school children [37]. Results also support the study by Baquet G et al. (2004) that reported improved aerobic capacity in children following high-intensity, intermittent-running aerobic exercises [38].

In addition the methodology of the current study does not agree with the design of Wilma J et al. (2008) which has used multiple components to improve physical activity in children. The study has described a lot about the minor aspects of the intervention but has lagged behind in demonstrating the information regarding PE sessions which is an important aspect in assessing the significance of the study. However standard parameters were used to assess the results (Euro Fit test) but the outcome of the study does not transmit any statistical significance. Also the study has not reported any gender comparison on the effect of intervention which is more likely to be seen in any objectively based study [39].

Supposedly there is only handful of studies that has worked on improving the health related physical activity in children. Study by Fairclough S. J et al. (2008) is an educational based intervention on improving the health related exercise in children [40]. The study had 5 classroom sessions, were knowledge of health related benefits of exercise were given to the children. Pre and post questionnaire were given to the children and assessment was made according to the marks scored by the children. The current study does not agree with this education based intervention because it seems unconvincing that children of age group 9-10 will voluntarily engage themselves in health enhancing exercises just by the effect of 5 class room sessions.-

The present study showed an overall higher aerobic fitness in boys than girls at the baseline. However, unlike other studies girls showed comparatively better improvement in fitness at the end of the intervention.

Maximum Heart Rate

Maximum Heart Rate (MHR) measurement was used to judge the intensity of the dance session to elicit aerobic fitness in children. The standard formula of calculating MHR is 220-age but is not preferred for pre pubertal children because their MHR generally range from 195 to 205 beats per minute and is independent of age [41]. As per the ACSM (American College Of Sports Medicine) guidelines the exercise intensity should reach 80 to 85 % of MHR to elicit cardio vascular response. The children in the intervention group reported MHR in the range of 160 to 190 bpm (approximately) which is in the range to have health benefits. In contrast to most of the studies girls surpass boys in MHR range during the intervention sessions.

Body Fat Percentage

Results suggested a significant increase in the weight of children in both the groups. This can be merely due to the children being at the age of pre pubertal growth spurt which leads to an increase in weight and height. Although the weight gain in children in the intervention group is comparatively lower then the control group. In respect to the measure of body fat percentage used in the current study, the findings indicate that the intervention also had positive impact on fat percentage compared to the control group. Future research is needed to understand the impact of exercise interventions on the relationship between weight status and body fat.

Strength

The intervention included a large study sample and the duration of the study was long enough to analyse the effectiveness of the intervention. The children were from the age group of 8-9 years (age from which decline in physical activity begins). Since the range is not vast the results are less prone to be biased. The availability of comparable data at baseline, mid and final level of the intervention was an advantage to assess the results of the intervention. Strength of this study also includes the direct measurement of VO2 max, body fat% and aerobic capacity using standard methods of assessment. Involvement of the professional coach for physical education session other then the regular PE teacher has worked as an asset for the study. The result of the study has proved the significance of MVPA in enhancing the health status of children.

Limitations

When interpreting our results the following limitations should be considered.

In total 95 children participated in the study but only a third were present for all the three measurements. This has affected the comparative results between baseline, intermediate and final data. Least number of students was present for the final measurement which might have affected the overall outcome of the study. In the mid of the study children went for Easter vacation and no home based program was given to maintain the effect of the intervention which has shown reverse results. Our scenario here supports the study by Aaron L et al which suggested a reversed intervention effects of the school based interventions during the summer vacations [42]. The physical activity hall in most of these schools were not big enough to have one 20 m running lap as required for 20 meter shuttle run test. A to and fro of 20 m were used to assess the aerobic capacity. Therefore some variation in the readings might be possible.

Future Research

Despite finding that a 16 week dance intervention enhanced the aerobic fitness in children, future research is required which can prove the long term benefit of physical activity at early age. Studies are required to understand the exercise physiology of girls and boys at the pre pubertal age. Importantly effect of skill based physical education in school system need to be established.

Studies are required to establish more effective strategies for encouraging health related physical activity in young children. Is concentrating on overweight or obese children for planning exercise program can be beneficial for better results? Are multiple short sessions of physical activity would be sufficient to get health related benefits compare to one long session of exercise. There are many hypotheses which need to be confirmed through more intense future researches.

CONCLUSION

Scotland urgently needs more research into physical inactivity and obesity along with useful data on trends in the epidemic of child obesity. The current study suggests the importance of skill based PE session along with the beneficial effect of additional physical education sessions on the health status of the children. A well planned entertaining PE session can have positive influence upon increasing physical activity levels in young children. The study also suggests that government should take steps to improve and increase the physical education in primary schools to combat physical inactivity and obesity in growing children.

References

www.who.int/dietphysicalactivity/publications/facts/pa/en/.

Torrance B., McGuire K.A., Lewanczuk R.. Overweight, physical activity and high blood pressure in children: a review of the literature, Vasc Health Risk Manag. 2007 February; 3(1): 139–149.

Kohl HW, Hobbs KE. Development of physical activity behaviors among children and adolescents. Pediatrics. 1998;101:549–554.

Tomkinson GR, Olds TS. Secular changes in aerobic fitness test performance of Australasian children and adolescents.Med Sport Sci. 2007;50:168-82 .

Tomkinson GR, Olds TS. Secular changes in pediatric aerobic fitness test performance: the global picture.Med Sport Sci. 2007;50:46-66.

Malina RM. Physical fitness of children and adolescents in the United States: status and secular change.Med Sport Sci. 2007;50:67-90.

Lukas Zahner,Jardena J Puder,Ralf Roth,Marco Schmid,Regula Guldimann, Uwe Pühse, Martin Knöpfli, Charlotte Braun-Fahrländer, Bernard Marti, Susi Kriemler. A school-based physical activity program to improve health and fitness in children aged 6–13 years (“Kinder-Sportstudie KISS”): study design of a randomized controlled trial [ISRCTN15360785], BMC Public Health. 2006; 6: 147.

Corbin CB, Pangrazi RP. Guidelines for Appropriate Physical Activity for Elementary School Children 2003 Update. Reston, VA: NASPE Publications; 2003.

Blair SN, Kohl HW, Gordon NF, Paffenbarger RS Jr, How much physical activity is good for health? Annu Rev Public Health. 1992;13:99-126

Telama R, Yang X, Viikari J, Välimäki I, Wanne O, Raitakari O, Physical activity from childhood to adulthood: a 21-year tracking study, Am J Prev Med. 2005 Apr;28(3):267-73.

Sleap M, Warburton P, Physical activity levels of 5-11-year-old children in England: cumulative evidence from three direct observation studies, Int J Sports Med. 1996 May;17(4):248-53.

Linsay Gray and Alastair H. Leyland. Overweight status and psychological well-being in adolescent boys and girls: a multilevel analysis, Eur J Public Health. 2008 December; 18(6): 616–621.

Weiss R, Dziura J, Burgert TS, Tamborlane WV, Taksali SE, Yeckel CW, Allen K, Lopes M, Savoye M, Morrison J, Sherwin RS, Caprio S. Obesity and the metabolic syndrome in children and adolescents. N Engl J Med.2004;350:2362–2374.

Nader PR, O’Brien M, Houts R, Bradley R, Belsky J, Crosnoe R, Friedman S, Mei Z, Susman EJ: Identifying risk for obesity in early childhood. Pediatrics 2006, 118:e594-601.

Freedman DS, Khan LK, Serdula MK, Dietz WH, Srinivasan SR, Berenson GS. The relation of childhood BMI to adult adiposity: the Bogalusa Heart Study. Pediatrics. 2005 Jan;115(1):22-7

Froberg K, Andersen LB., Mini review: physical activity and fitness and its relations to cardiovascular disease risk factors in children, Int J Obes (Lond). 2005 Sep;29 Suppl 2:S34-9.

Lee IM. Physical activity and cancer prevention — data from epidemiologic studies. Med Sci Sports Exerc 2003; 35:1823-7.

Warburton DE, Nicol CW, Bredin SS. Health benefits of physical activity: the evidence. CMAJ. 2006 Mar 14; 174(6):801-9.

Darla M. Castelli, Charles H. Hillman, arah M. Buck, and Heather E. Erwin. Physical Fitness and Academic Achievement in Third- and Fifth-Grade Students, Journal of Sport & Exercise Psychology, 2007, 29, 239-252.

Churchill JD, Galvez R, Colcombe S, Swain RA, Kramer AF, Greenough WT. Exercise, experience and the aging brain. Neurobiology of Aging. 2002; 23(5):941–955.

Trish Gorely, Mary E Nevill, John G Morris, David J Stensel, Alan Nevill. Effect of a school-based intervention to promote healthy lifestyles in 7–11 year old children, Int J Behav Nutr Phys Act. 2009; 6: 5.

Danielzik S, Pust S, Muller MJ: School-based interventions to prevent overweight and obesity in prepubertal children: process and 4-years outcome evaluation of the Kiel Obesity Prevention Study (KOPS). Acta Paediatr Suppl 2007, 96:19-25.

Manios Y, Moschandreas J, Hatzis C, Kafatos A: Health and nutrition education in primary schools of Crete: changes in chronic disease risk factors following a 6-year intervention programme. Br J Nutr 2002, 88:315-324.

Sallis JF, McKenzie TL, Alcaraz JE, Kolody B, Faucette N, Hovell MF: The effects of a 2-year physical education program (SPARK) on physical activity and fitness in elementary school students. Sports, Play and Active Recreation for Kids. Am J Public Health 1997, 87:1328-1334.

Nakeeb Y., Duncan M., Lyons M, & Woodfield L. Body fatness and physical activity levels of young children, Annals of Human Biology, January–February 2007; 34(1): 1–12.

Serbescu C, Flora D, Hantiu I, Greene D, Laurent Benhamou C, Courteix D. Effect of a six-month training programme on the physical capacities of Romanian schoolchildren, Acta Paediatr. 2006 Oct; 95(10):1258-65.

Armstrong N. 1998. Young people’s physical activity patterns as assessed by heart rate monitoring. J Sport Sci 16:S9–S16.

Sung RY, So HK, Choi KC, Li AM, Yin J, Nelson EA. Body fat measured by bioelectrical impedance in Hong Kong Chinese children, Hong Kong Med J. 2009 Apr;15(2):110-7.

Houtkooper LB, Lohman TG, Going SB, Howell WH. Why bioelectrical impedance analysis should be used for estimating adiposity, Am J Clin Nutr. 1996 Sep;64(3 Suppl):436S-448S. Review.

C Mahoney, 20-MST and PWC170 validity in non-Caucasian children in the UK, Br J Sports Med. 1992 March; 26(1): 45–47.

V J Paliczka, A K Nichols, and C A Boreham, A multi-stage shuttle run as a predictor of running performance and maximal oxygen uptake in adults, Br J Sports Med. 1987 December; 21(4): 163–165.

Ramsbottom R, Brewer J, Williams C: A progressive shuttle run test to estimate maximal oxygen uptake. Brit J Sports Med 1988, 22(4):141-144.

Harrell JS, McMurray RG, Bangdiwala SI, Frauman AC, Gansky SA, Bradley CB: Effects of a school-based intervention to reduce cardiovascular disease risk factors in elementary-school children: the Cardiovascular Health in Children (CHIC) study. J Pediatr 1996, 128:797-805.

SL Gortmaker, K Peterson and J Wiecha et al., Reducing obesity via a school-based interdisciplinary intervention among youth: Planet Health, Arch Pediatr Adolesc Med 153 (1999), pp. 409–418.

P Sahota, MCJ Rudolf, R Dixey, AJ Hill, JH Barth and J Cade. Evaluation of implementation and effect of primary school based intervention to reduce risk factors for obesity, BMJ 323 (2001), pp. 1027–1029.

M Story, M Evans, RR Fabsitz, TE Clay, BH Rock and B Broussard. The epidemic of obesity in American Indian communities and the need for childhood obesity-prevention programs, Am J Clin Nutr 69 (1999) (suppl), pp. 747S–844S.

Dwyer T, Coonan WE, Leitch DR, Hetzel BS, Baghurst RA, An investigation of the effects of daily physical activity on the health of primary school students in South Australia, Int J Epidemiol. 1983 Sep;12(3):308-13.

Baquet G, Guinhouya C, Dupont G, Nourry C, Berthoin S. Eff