Physical fitness, nutritional habits and daily locomotive action of 12-year-old children with different body mass index

Objective. The purpose of this study was to examine the differences in physical fitness, daily nutritional habits and locomotive behaviour among pupils with varying body mass index (BMI) in the 5th and 6th grades of primary school. Design. The sample consisted of 480 pupils (229 boys and 251 girls), who participated in specific Eurofit tests and completed questionnaires probing their physical activity and nutritional habits. They were divided according to their BMI into normal, overweight or obese children. Main outcome measures. 18% and 8% of the pupils were categorised as overweight and obese, respectively. Results. From the data analysis (two-way ANOVA), with BMI and gender as independent variables, it was found that the obese and overweight pupils had lower performance in long jump, in 30-m speed and in 20-m shuttle run. They adopted sedentary daily habits, such as many hours of TV watching and unhealthly nutritional habits. Conclusions. The results of this study support the need for intervention at school through physical education and health education lessons, to inform pupils about the health risks associated with limited physical activity and unhealthy nutritional habits. Another goal should be to motivate and create behaviours that are conducive to better lifestyle habits.


Introduction
Physical activity is important for the health status of any age group, and especially for young people.Studies show that children and adolescents who participate in regular physical activity can gain psychological health and skeletal health benefits. 3Regular physical activity is associated with enhanced health and reduced risk of all-cause mortality, it improves aerobic capacity, muscular strength, body agility, co-ordination and metabolic functioning, exemplified by improvements in bone density, lipid profiles, insulin levels and immune function. 28Those who are physically active have a reduced risk of developing cardiovascular disease and ischaemic stroke, 30 non-insulin-dependent (type 2) diabetes, 12 colon cancers, 2 and osteoporosis. 25Physical activity is also consistently related to higher levels of self-esteem and lower levels of anxiety and stress.27   However, while the positive effects of regular physical activity are well established in children and adolescents, there is evidence that young people in many developed nations do not participate in regular physical activity of the type and intensity associated with health.As a result, the prevalence of childhood obesity is increasing worldwide. 19Since obesity is associated with increased morbidity and mortality, the World Health Organization has compared the marked increase to a global epidemic disease.

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The overweight and obese child is not physically active, has a sedentary way of life and no interest in exercise.Psychological consequences of obesity may have a powerful effect on the self-image and social standing of the overweight and obese child during critical phases of emotional development.Studies evaluating the influence of obesity on mental health portray a disturbing picture of depression, low self-esteem, poor body image, and social isolation.The failure to achieve success with dieting and other therapeutic interventions may potentiate these negative feelings, and the inability to participate in physical activity and discrimination by peers and adults are further contributing influences.

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Many studies have shown that obese children and adolescents are physically less active and less fit than their non-obese peers. 9Physical fitness is generally considered to be 'the ability to perform daily tasks without fatigue'.Physical fitness includes several components: cardiorespiratory fitness, muscular endurance, muscular strength, flexibility, co-ordination and speed.
Increasing physical activity is one of the key elements in the treatment of childhood obesity. 23However, motivating obese subjects to adhere to an activity programme is a major challenge. 26To improve adherence one must develop an exercise programme that is manageable for obese children and adolescents. 23Interventions that are not tailored to the fitness levels of obese participants may discourage future participation in physical activity.The ability to develop physical activity programmes suited to obese participants requires further investigation of different components of physical fitness in this population.
The purpose of this study was to examine the differences in physical fitness, daily nutritional habits and locomotive behaviour among pupils with varying body mass index (BMI) in the 5th and 6th grades of primary school.The hypothesis of the research is that overweight and obese children will have differences in fitness levels and they will adopt a sedentary lifestyle.

Material and methods participants and study design
The study included 480 children (229 boys and 251 girls) aged 11 -12 years (mean 11.62 ± 0.60 years), attending the 5th and 6th grade classes of primary schools which were selected with stratified sampling in suburban and urban areas of west-northwest Greece.The nature and purpose of the study were explained to parents before consent was obtained, and participation was on a voluntary basis.The measurements and the tests that the children underwent were carried out during the first two school hours.The data collected included anthropometric measurements as well as motor-and health-related fitness parameters.

Anthropometric measurements
Age (accurate to 1 month) was recorded.Height was measured with a stadiometer to the nearest 0.5 cm.Body mass was measured on a balance-beam scale accurate to 0.1 kg.The students were barefoot, wearing light clothing to decrease the additional weight.Body mass index (BMI) was calculated by dividing weight by height squared (kg.m -2 ). 7

Physical fitness measurements
The physical fitness of the children was evaluated with the Eurofit test battery, 8 which is designed for the assessment of healthrelated fitness in children and adults.Eurofit for children is designed to be practical and applicable under conditions available in ordinary communities.The children wore athletic shoes and athletic clothes and underwent the following tests that measure different components of fitness.
• Sit and reach (SAR): Reaching as far as possible from a sitting position.This test measures the flexibility of posterior muscles.
• Standing long jump with feet together (SLJ): The maximum horizontal distance attained was measured.This test evaluates the explosive strength of the legs.
• Sit-ups (SUP): The maximum number of sit-ups achieved in 30 seconds was recorded.This test measures the trunk strength (muscular endurance).
• Overhand throw: The test measures the strength of the upper body limbs.
• 20-meter multistage aerobic shuttle run test (MAT): This test evaluates the maximum aerobic capacity based on an indirect-incremental-maximum field test involving a 20-meter shuttle run, using the formula proposed by Léger et al. to calculate the maximal oxygen consumption (VO2max). 16

students' daily locomotive and nutritional habits
Responders were asked how often and how many times each week they 'participated in sports, swimming or other physical activities, excluding mandatory physical education classes in school'.They were also asked about their nutritional habits during the last week and about their sedentary habits ('How many hours do you watch TV on a week day and on the weekend?').

statistical analyses
Descriptive statistics were performed for all parameters.A twoway ANOVA was used to examine differences in group means.A Sidak post hoc test was used to identify differences among gender and BMI categories (Sidak was used to compare variables from different data collections) and effect sizes (η 2 --i.e.proportion of the total variance that is attributed to an effect) were calculated to assess the significance of the differences in fitness performance among BMI categories.Comparisons were considered significant at a p-value of 0.05 or less.Chi-square tests were used to detect differences between normal, overweight and obese children in their daily locomotive and nutritional habits.SPSS version 11.0 software was used for all statistical calculations.

Results
When the entire sample including both genders was analysed, 74% of the participants had a normal BMI, 18% were overweight and 8% were characterised as obese.
The differences in the fitness parameters among BMI categories by gender are presented in Table I.Two-way ANOVA results revealed a significant effect of BMI and gender in the multistage aerobic shuttle run test (p=0.001,η 2 =0.028), and in flexibility (p=0.002,η 2 =0.025).Specifically, normal boys performed better than their obese counterparts in standing long jump (p=0.000,η 2 =0.111), in sit-ups (p=0.010,η 2 =0.019), in sprint (p=0.000,η 2 =0.237), and in the multistage aerobic shuttle run test (p=0.001,η 2 =0.08).In addition, overweight boys demonstrated better performance than obese boys in the standing long jump, the overhand throw, sprint and in the multistage aerobic shuttle run test (p-values between 0.004 and 0.001).Normal-weight girls performed better in the sprint than their overweight and obese counterparts (p=0.001).In the comparison of physical fitness tests between genders within the BMI categories, boys obtained better results than girls for all tests except flexibility.
Tables II and III present the results of chi-square tests examining the differences between some discernible variables related to the daily athletic, locomotive and nutritional habits.Significant differences were found between the three cohorts, with the obese children displaying a higher percentage in all categories.

Discussion
The principal findings in the present study were that obese and overweight pupils had lower performance in specific physical fitness tests and they adopted sedentary daily habits, such as many hours of TV watching and unhealthy nutritional habits.Our results support the findings of previous studies in Greece 20,10,18   and in other countries 4,29 that the prevalence of overweight and obesity in 10 -12-year-olds was approximately 30%.
The results showed that overweight and obese students had inferior performances in all tests requiring propulsion or lifting of the body mass (standing-broad jump, sit-ups, and endurance shuttle run).These poorer performances in obese individuals are probably due to the fact that their excess body fat is an extra load to be moved during weight-bearing tasks.Another explanation could be that obese children and adolescents avoid weightbearing activities because of the greater energy cost compared with normal-weight children.In this case, the poorer performance could also be a consequence of a lack of experience in weightbearing tasks.Because obese young boys and girls are limited in their ability to perform weight-bearing activities, such activities should be limited at the start of an intervention programme.Activities that are not tailored to the capabilities of bigger children may discourage continued participation by obese individuals.9 Once levels of fatness have decreased and/or fitness levels have improved, weight-bearing tasks may be much less exhausting and should be progressively included in the programme.9   No relationship was found between obesity and flexibility, something that was mentioned in previous studies. 21Useful non-weight-bearing alternatives such as cycling, swimming or other aquatic activities should be the focus in the early stages of programme and then continued as an appropriate means of balancing various types of activity.

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The second research question was related to differences in the children's nutritional habits and in their daily locomotive habits.Results showed that overweight and obese children watched more hours of TV in the weekday and the weekends.Other studies have also found negative relationships between television viewing times and obesity. 14Television watching replaces more vigorous activities.There is a positive correlation between time spent watching television and being overweight or obese in populations of different ages.Prevalence of obesity has increased as well as the number of hours that TV networks dedicate to children. 13In addition, children are exposed to many unhealthy stimulations in terms of food intake when watching television.Over the last few years, the number of television food commercials targeting children have increased, especially junk food.The current use of food in movies, shows and cartoons may lead to a misconception of the notion of healthy nutrition and stimulate an excessive intake of poor nutritional food. 5 Another finding of this study was that overweight and obese children were less likely to join an organised athletic club.Sports clubs may be too competition oriented and therefore not appropriate for the less-fit children and adolescents, which  would include the obese.Given the commonly low levels of sports participation by the obese, the encouragement of sports participation from an early age may be important in the prevention and treatment of overweight. 9 No relationship was found between video game/computer use and the BMI among children.This may be because primary school children in this study spent relatively little time in these activities, because these activities are less sedentary than television viewing, or due to other factors which were not explored in this study (i.e.no food advertising, hands not free for eating during video game/computer use).There is not much research to which we could compare our findings.

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The phenomenon of fatness and all its contributory factors in childhood and adolescence is an important problem -it can become one of the most common diseases and can turn into a world-wide epidemic.Important causes for this are lack of physical activity and sedentary lifestyle.A goal for managing the overweight and obese children is to urge them to become physically active, in an attempt to influence them to adopt these habits as adults.In addition to the physical effects, this will also have psychological and social benefits. 22Exercise programmes include lifestyle changes, e.g.walking instead of taking a bus, using stairs instead of lifts, as well as exercise in a planned and structured manner, e.g.participating in sport or gymnastic groups.
Another aspect is that inactive periods (sedentary activities, TV and video viewing, etc.) during the day should be exchanged as much as possible for active behaviour.Recent studies suggest that decreasing sedentary activity is very effective in promoting weight loss. 32Strategies to increase physical activity are therefore key elements in the treatment of childhood obesity, along with changes in eating behaviour.

TABle III . Results of chi-square test concerning daily athletic and locomotive habits Chi-square test
*Values significantly different (p<0.05).