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On-line version ISSN 1678-4782
J. Pediatr. (Rio J.) vol.85 no.1 Porto Alegre Jan./Feb. 2009
Influence of programmed physical activity on body composition among adolescent students
Edson S. FariasI; Flaviano PaulaII; Wellington R. G. CarvalhoIII; Ezequiel M. GonçalvesIII; Alexandre D. BaldinIII; Gil Guerra-JúniorIVIDoutorando, Curso de Pós-Graduação em Saúde da Criança e do Adolescente, Faculdade de Ciências Médicas, Universidade Estadual de Campinas (UNICAMP), Campinas, SP, Brazil. Laboratório de Crescimento e Composição Corporal, Centro de Investigação em Pediatria (CIPED), Departamento de Pediatria, Faculdade de Ciências Médicas, UNICAMP, Campinas, SP, Brazil. Professor, Departamento de Educação Física e Desporto, Universidade Federal do Acre (UFAC), Rio Branco, AC, Brazil
IIEducador físico. Universidade Federal de Rondônia (UNIR), Porto Velho, RO, Brazil
IIIDoutorando, Curso de Pós-Graduação em Saúde da Criança e do Adolescente, Faculdade de Ciências Médicas, UNICAMP, Campinas, SP, Brazil. Laboratório de Crescimento e Composição Corporal, CIPED, Departamento de Pediatria, Faculdade de Ciências Médicas, UNICAMP, Campinas, SP, Brazil
IVProfessor livre-docente, Departamento de Pediatria, Faculdade de Ciências Médicas, UNICAMP, Campinas, SP, Brazil. Laboratório de Crescimento e Composição Corporal, CIPED, Departamento de Pediatria, Faculdade de Ciências Médicas, UNICAMP, Campinas, SP, Brazil
ABSTRACTOBJECTIVE: To verify the influence of programmed physical activity on body composition among adolescent students during 1 school year.
METHODS: The sample included 383 students (age range: 10 to 15years) separated into two groups: 186 cases (96 male and 90 female) and 197 controls (108 male and 89 female). This was an intervention study with pre- and post-test assessments in which interventions consisted of programmed physical activity; the control group had conventional school physical education. Body composition was assessed by anthropometric measurements, body mass index (BMI), body fat percentage and fat and lean body mass.
RESULTS: In the case group, subscapular skinfold thickness, BMI, body fat percentage and fat body mass remained stable; there were significant reductions in tricipital skinfold thickness and in abdominal perimeter among girls and significant increases in arm, waist and calf perimeters and in lean body mass. In the control group, there were significant increases in BMI, tricipital skinfold thickness, abdominal perimeter and fat body mass among girls. At post-test, overweight and obesity significantly decreased among case group subjects, but not among controls.
CONCLUSION: Programmed physical activity resulted in improvement or maintenance of body composition parameters and in reduction of overweight and obesity in the intervention group.
Keywords: Motor activity, school health, body composition, obesity, overweight.
The technological changes of the past decades have made children and adolescents less active, which has contributed to increasing the frequency of overweight and obesity among the age group.1,2 Obesity has multifactorial etiology, but its primary physiopathology is the high ratio of calorie intake to calorie consumption. The energy imbalance leads to accumulated energy in adipocytes, causing hypertrophy, hyperplasia, and abnormalities in adipocyte function, especially endoplasmic reticulum and mitochondrial function. Intracellular and systemic consequences include insulin resistance, adipokine production, free fatty acids, inflammatory mediators, and the promotion of systemic dysfunction which are seen in the clinical manifestations and sequelae of obesity.3
Thus, overweight/obese children and adolescents have come to suffer from adult diseases: some early in life, such as psychosocial conditions, depression, isolation, and low self-esteem; and others later in life, such as high blood pressure, diabetes, and cardiovascular disease.3-6 Ferreira et al.7 have found a relationship between metabolic syndrome (MS) and risk factors for cardiovascular disease and insulin resistance among obese children, data confirmed by a review by Lottenberg et al.8
Physical activity can foster key changes in body composition and lean mass, thus becoming an important factor in controlling overweight/obesity among children and adolescents. Metanalysis assessing treatment of pediatric obesity has shown that there are limitations to the effects of pharmacological interventions and short term changes in lifestyle (under six months of treatment).9 However, reviews of long term studies (over 12 months of practice) have shown promising results for the influence of physical activity on lifestyle changes and, consequently, on body composition, both for preventing and for treating overweight/obesity among children and adolescents.10-12
Therefore, the goal of this study was to assess the influence of programmed physical activity on body composition among adolescents during 1 school year.
The present study was approved by the research ethics committee of the Universidade Estadual de Campinas (UNICAMP) Faculdade de Ciências Médicas (Report no. 218/2005). The study was undertaken in the city of Porto Velho, Rondônia, in northern Brazil, with the approval all school directors and parents/guardians of schoolchildren involved.
All students included in the study were enrolled in grades five through eight in 2006 and regularly attended classes. Students with permanent or temporary physical impairments which hindered anthropometric measurements were excluded from the study, as well as those which missed over 25% of all Physical Education classes during the study. When the study began, the sample consisted of 497 students, but it decreased due to personal complications (loss = 53 students), and the need at the end of the study to adjust sample size to increase the statistical discriminatory power of the variables (loss = 61 students); the study finished with 383 students, all ranging from 10 to 15 years old.
This is a longitudinal intervention study with pre- and post-tests in which students were intentionally divided into two groups: students from Colégio Adventista were assigned to the case group (n = 186), while students from Colégio Objetivo were assigned to the control group (n = 197).
Both groups were submitted to two 60-minute physical education classes per week, totaling 68 classes during the school year. Control group students performed physical activities considered routine in the school, such as playing games, calisthenics, learning the fundamentals of particular sports, and playing sports. Meanwhile, case group students were submitted to programmed physical activity, with the maximum heart rate (HRmax)13 of each student monitored by the Geonaute® CW 500.0 heart rate monitors. Initially, the case group performed light intensity physical activities, with 40 to 55% HRmax,13 for a maximum period of 1/3 of the study, time needed to allow it to jump to 55 to 75% HRmax.13 Classes consisted of three sections: first, aerobic activity (flexibility exercises, jumping rope, walking, alternating running, jumping in continuous rhythm, recreational games) for 30 minutes; second, playing sports (volleyball, indoor soccer, handball, swimming) for 30 minutes; and, third, stretching for 10 minutes.
Early in the study, case and control groups were similar in terms of age, gender, socioeconomic status (as assessed via survey, using the Brazilian Associação Nacional de Empresas de Pesquisa (ABEP) classification14) (Table 1), and puberal development (self-assessed, according to breast stage for girls15 and genital stage for boys16) (Table 2). The data did not significantly diverge at the end of the study.
Body composition was assessed using anthropometric weight (kg), height (cm), subscapular and tricipital skinfold (cm), arm, waist, abdomen and calf perimeter (cm) measurements, following standards set by Petroski et al.17 All measurements above were taken at the beginning and the end of the study.
Body composition measurements were used to calculate:
- Body mass index (BMI) (kg/m2), data turned into z score,18 and students assessed as normal if zBMI ≤ 1.0, overweight if zBMI > 1.0 and < 2.0, and obese if zBMI > 2.0.
- Body fat percentage (fat percentage), from equations developed by Slaughter et al.19 Such equations use the tricipital and subscapular skinfolds, and take gender, race (black and white), and sexual maturity into consideration.
- Fat and lean masses (kg), using the formula from Behnke e Wilmore20: fat mass (FM) = weight (kg) X (fat percentage/100) and lean mass (LM) = weight - FM.
To determine the statistical power of the sample, we used the fpower SAS software application, which calculates the sample size needed to achieve a certain power. After defining sample size, all variables had discriminatory power over 80%, and most were above 90%.
The similarity between the two schools for gender and socioeconomic status was assessed using the chi-square test; similarity in age and puberty was assessed using the Mann-Whitney test. Analysis of variance (ANOVA), corrected for age and socioeconomic status, was used to compare measurements between groups (cases and controls), genders (male and female), and time (pre- and post-test). BMI z score between assessments were compared using the symmetry test and McNemar's test. A 5% significance level was adopted for statistical tests.
Table 3 shows results for weight, height, BMI, subscapular and tricipital skinfolds, arm, waist, abdomen and calf perimeters, fat and lean and fat mass percentages. The data were assessed according to gender (male and female), type (case and control groups), and time (pre- and post-test), and adjusted for age and socioeconomic status (repeated-measures ANOVA).
Weight was significantly higher for boys than for girls (p = 0.02) and at post-test than at pre-test (p < 0.01). Height was significantly higher at post-test than at pre-test only for the case group (p = 0.01), and for boys than for girls only at post-test (p < 0.01). BMI was significantly higher at post-test than at pre-test only among controls (p = 0.03).
For subscapular and tricipital skinfolds, overall, values were higher for girls than for boys, at pre-test than at post-test, and for controls than for cases. The subscapular skinfold was significantly higher at post-test for controls than for cases (p < 0.01). Tricipital skinfold was significantly higher for girls than for boys (p = 0.04), at pre-test than at post-test (p < 0.01), and among controls than among cases (p = 0.04).
For arm, waist, abdomen and calf perimeters, overall, values were higher for boys than for girls, at post-test than at pre-test, and for controls than for cases. Arm perimeter was significantly higher at post-test than at pre-test for the case group (p = 0.04). Waist perimeter was significantly higher for boys than for girls (p < 0.01), and at post-test than at pre-test (p < 0.01). Abdominal perimeter was significantly higher for boys than for girls (p = 0.03) and for control than for cases (p = 0.03). Calf perimeter was significantly higher for boys than for girls (p = 0.03) and at post-test than at pre-test (p = 0.02).
Fat percentages were significantly higher at pre-test than at post-test (p < 0.01), and fat mass greater at post-test than at pre-test in the control group (p = 0.04). Lean mass was significantly higher for boys than for girls (p < 0.01), and at post-test than at pre-test (p < 0.01).
Table 4 shows the frequency of obesity and non-obesity (normal and overweight) cases according to BMI z score, divided into cases and controls and pre- and post-test. The case group saw significant drops in the ratio of obesity at post-test (24.7%) from pre-test (29%) (p = 0.04). The same drop was not found in the control group, which had 35.5% obese subjects at pre-test and 32% at post-test (p = 0.09).
Regular physical activity programs have only come under greater scrutiny in the last few years. However, over time, several studies have sought to investigate the effects of this sort of training in improving different components of body composition.9-12,21
After adjusting for age and socioeconomic status before and after the intervention period, the results show changes in body composition variables, with a trend of decreasing body adiposity among the case group unseen among controls, especially in skinfolds, fat percentage, and fat mass.
For adolescents, we should stress that changes are not always so appreciable due to metabolic changes produced during the training process,21 and, primarily, due to changes in growth and body composition characteristic of growth spurts and sexual maturation,22 when as a rule a positive energy balance is needed for accumulation as fat during this stage of development.23
Changes in skinfolds, especially the tricipital skinfold, with decreases in post-test values, especially for the case group, were also seen by other authors.24,25 In this study, arm perimeter increased significantly in relation to time for the case group, but remained stable among controls. Calf perimeter had time and gender differences for both groups. Arm and calf perimeters increased, except for female case arms, with higher results for boys, perhaps because of the prevalence of muscle development in these regions of the body among men. Possible factors for these results are strength work of the lower and upper limbs (arm, thigh, and leg) through physical training developed during school physical activity, with greater fat burn and stimuli for muscles in the region; the intrinsic male characteristic of having greater muscle mass than girls; the fact that boys are more active than girls, especially in moderate and high physical activities which demand greater strength.
Waist and abdominal perimeters are strong indicators of subcutaneous and visceral adiposity. They are highly correlated to individual predisposition to conditions such as diabetes and cardiovascular disease.3-8 There were significant differences between both study groups (case and control) in the gender variable, showing greater enhancement for boys than for girls in terms of waist and abdomen measurements pre- and post-test. Such findings may be related to body composition characteristics determined by gender during puberty.
Regarding fat percentage, both male and female subjects from the case group had decreases at post-test over pre-test measurements, but the same was not found in the control group, especially for girls. Thus, at the end of puberty, girls have proportionally twice as much fat as boys. Some intervention studies26,27 done with adolescents show similar results regarding fat percentage.
The study showed significant increases in lean mass for time and gender in both study groups. This result can also be explained by the body changes which coincide with the growth spurts of puberty. However, fat mass decreased for both genders in the case group from pre- to post-test, which was not true for controls, which saw increases in fat mass. This data point can be associated to the positive effect the intensity of programmed physical activity had on fat mass directly. Changes from physical activity with increases in lean mass and decreases in fat mass are well documented in the literature.28,29
The current study also showed significant drops in the frequency of obesity in the case group (but not among controls) at post-test over pre-test. Therefore, we can say that physical activity focused on promoting health, done during school activities, even if it does not promote significant decreases in body fat, while compliance lasts does at least prevent its increase. This is true even during puberty, a stage in people's lives in which changes in body composition more often predispose adolescents to increases in body adiposity.
We would like to thank CNPq (E.S.F. and E.M.G.) and CAPES for doctoral scholarships (W.R.G.C. and A.D.B.), and to the Physical Education teachers of every school for their aid in our assessments.
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Manuscript received Sep 17 2008, accepted for
publication Dec 01 2008. Financial support: CNPq (bursary students: E.S.F.
and E.M.G.) and Capes (bursary students: W.R.G.C. and A.D.B.).
Departamento de Pediatria - CP 6111
Faculdade de Ciências Médicas - UNICAMP
CEP 13083-970 - Campinas, SP - Brazil
Tel.: +55 (19) 3521.8923
Fax: +55 (19) 3521.8925
No conflicts of interest declared concerning the publication of this article.
Suggested citation: Farias ES, Paula F, Carvalho WR, Gonçalves EM, Baldin AD, Guerra-Júnior G. Influence of programmed physical activity on body composition among adolescent students. J Pediatr (Rio J). 2009;85(1):28-34.
Manuscript received Sep 17 2008, accepted for publication Dec 01 2008.
Financial support: CNPq (bursary students: E.S.F.
and E.M.G.) and Capes (bursary students: W.R.G.C. and A.D.B.).