The decrease in the amount of motor activity observed on children and adolescents in different socioeconomic spectra 1 has raised interest in the knowledge of physical fitness and health, in order to classify it from scores based on referenced criteria both nationally and internationally, which involve physical qualities able to reflect patterns of behavior and environmental.

Closely related to the health, the low levels of cardiorespiratory fitness (CFR) on childhood and adolescence are associated with an increased early death risk due to any cause, especially cardiovascular diseases. 2,3 So the prevention of cardiovascular diseases should begin still during the school stage, given that the adoption of healthy attitudes on that age range is perpetuated into adulthood.

In this way it is important to detect in advance, even within the school environment, children and adolescents with a predisposition to low aerobic fitness. In this sense, the development of mathematical models for predicting CRF without exercise test could be feasible in epidemiological studies 4 and very useful for physical education teachers.

From this perspective, the presented study aimed to evaluate the CRF and the BMI of schoolchildren of both sexes according to the cutoff points established by the Fitnessgram®, as well as determine the influence of BMI on CRF of children and propose an equation for predicting VO2max from the body composition.

The results of anthropometric variables observed in Table 1 were similar when comparing both sexes, regarding age, height, body mass (BM) and BMI. In terms of percentage of body fat, females had higher values (t = 6.049, p < 0.0001), and the boys showed higher values for maximum oxygen consumption (t = −4.106, p < 0.0001).

Regarding the behavior of BMI in both sexes (Fig. 1), it may be noted no differences based on established criteria. Considering the cutoff points for the Fitnessgram®, 9.2% of girls were classified as “below”, 80.3% “normal,” and 10.5% “above”, the values considered in the same way for males were respectively, 8.2%, 79.5% and 12.3%.

Fig. 1.

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Relative values by sex, following the Fitnessgram cutoffs established for the Body Mass Index, BMI (kg/m2).

In relation to VO2max (Fig. 2), the percentage of boys classified as ‘above’, according to the cutoffs of the Fitnessgram®, was higher (41.8%) than the percentage of girls (19.7%). No statistically significant difference was found between girls and boys in the other classifications. The percentage of boys and girls classified as ‘below’ were 44.5% and 57.1%, respectively. The percentage of boys and girls classified as ‘normal’ were 13.7% and 23.2%, respectively.

Fig. 2.

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Relative values by sex, following the Fitnessgram cutoffs established for the VO2max (ml kg min–1). *p < 0.05: statistically significant difference between male and female; %: percentage; VO2max: maximal oxygen uptake.

Both Figs. 3 and 4 show the correlation between the two variables, as well as the influence of the independent variable, BMI exerts on the dependent, VO2max, by determining the simple linear regression and the R 2 value. This behavior was evaluated in both sexes and as many girls (R 2 = 0.907) as boys (R 2 = 0.850) presented strong correlation.

Fig. 3.

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Simple linear regression curve for the relationship between BMI and VO2max in males (R 2 = 0.850). VO2max: maximal oxygen uptake; BMI: body mass index.

Fig. 4.

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Simple linear regression curve for the relationship between BMI and VO2max in females (R 2 = 0.907). VO2max: maximal oxygen uptake; BMI: body mass index.

Analyzing Table 2, it was found in the study group a strong relationship in both sexes between the dependent and independent variables.

The present study aimed to evaluate the cardiorespiratory fitness and the BMI of schoolchildren of both sexes according to the cutoff points established by the Fitnessgram®, as well as determine the influence of BMI on CRF of children and propose an equation for predicting VO2max from the body composition.

There was a low compliance to the Fitnessgram® criteria associated with risk of obesity (Fig. 1). These results were better than those found by Bergmann et al., 12 in a study with students of 13–14 years old in the city of Canoas (Rio Grande do Sul, Brazil). In that occasion the authors detected 19% of boys and 15% of girls outside the health criteria recommended by Projeto Esporte Brasil (PROESP-BR). This may be attributed to the changes and differences in lifestyles of each region or country. 13

In relation to other national studies, such as Hobold and Hübner 14 with students of 10–14 years old, the BMI behaved as ‘below’, for both female and male from the city of Marechal Cândido Rondon (Paraná, Brazil). Ronque et al. 15 in adolescents aged 10–15 years old from the city of Londrina (Paraná, Brazil), obtained higher BMI values than the present study, in individuals with low and high cardiorespiratory fitness based on the criteria of the Fitnessgram®. However, the sample here studied remained above the schoolchildren from the Vale do Cotinguiba (Sergipe, Brazil) studied by Petroski et al. 16 Although with respect to Spanish 7–12 years old school children from Aragón, have shown to be equivalent. 17

The investigation of morphological parameters becomes more relevant when detects possibilities of body fat accumulation, the emergence of chronic diseases and cardiovascular diseases. Malina and Bouchard 18 emphasized that the female acquires greater gains of fat mass than boys from late childhood to late adolescence.

In this sense, the BF% (Table 1) of both groups were higher than those obtained by Dellagrana et al. 19 and Hobold and Hübner. 14 In this perspective, Lloyd et al. 20 in students aged 10–12 years old from Texas – USA, found a BF% of 14.3 in males, at the same level of this study, although the female showed 8.5%, a value very below the results of this study. Despite variations, these results put the sample of this study far from risk of overweight and obesity according Fitnessgram® criteria. 21 This evidence was corroborated by the parameters of the BMI (Fig. 1), which also report levels below normal.

Several studies 22–25 over the past decade have reported the trend towards a minor cardiorespiratory fitness on female school students compared to their male counterparts. This phenomenon can be explained by sudden changes in body composition during puberty, particularly fat mass for girls. 18 In addition to this, LaMonte et al. 26 obtained that the maximal oxygen consumption is inversely proportional to BMI, in addition to other serum lipid parameters.

It was evidenced that the CRF of males was higher than females, while for the BMI, there were no differences between the groups. While most of the group remained in the normal range for BMI (79.9%), it drew attention to the high prevalence of the entire sample (50.8%) with poor performance for VO2max, particularly with respect to the female group, which 57.1% of them did not fit the health criteria adopted by Fitnessgram®. Furthermore, we proved the hypothesis of an inverse relationship between VO2max and BMI, in children and adolescents, a crucial period of life to develop these physical qualities. 27

Because it is an important functional aspect, which if neglected in childhood and adolescence leads to extreme damage to health in adulthood, the result of this study on CRF requires specific attention by the government and educational authorities. It is well known the secular trend in the decline of this physical quality by several factors, including increased time spent in sedentary behaviors, like a high rate of exposure to television. 28

This transition to sedentary lifestyle and its effects are strengthened by the phenomenon of urbanization of the society, as reported Chillón et al., 29 who studied spanish schoolchildren from antagonistic geographic areas, rural and urban, where lower levels of VO2max were found in the urban school children compared to their rural peers. Data from two cross-sectional studies in adolescents of 12.5-17.5 years old from Zaragoza (Spain) revealed an increase in CRF over 5 years. 30 According to the authors, these data follow the opposite to the consistent decrease in cardiorespiratory fitness identified by studies around 27 countries and five geographic regions around the world.

The fact that the data from this study are aligned with the global trend is worrying, because low levels of this variable are related to risk of cardiovascular diseases, which begin in childhood and progress silently until adulthood, and are associated with a high number of deaths in some populations. 22,31,32 The low performance of students from Aracaju (present study) on 20 m shuttle-run test – only one boy for every ten (13.7% and one girl for every five (23.2%) met the cutoff points proposed by Fitnessgram® – contrasts with the results obtained by Guedes et al., 33 who found that about 50% on both boys and girls, reached health criteria. According to the authors, these results are not optimistic, especially because they observed a decline in proportion when increasing age, especially in physical tests that involve large muscle groups.

Usually, girls tend to be more affected by the advancement of puberty, as was also seen in Rodrigues et al., 34 who found an increase in aerobic power in men, from 43.5 to 49.5 ml kg/min. However, similar to the present study, it was observed a decrease in values from 38.3 to 36.8 ml kg/min on female, within the age range studied. In turn, 46.0% of students in Canoas (Rio Grande do Sul, Brazil) 12 reached the zone of normality. Both studies corroborate the performance reached by the students from the present sample.

The development of estimative equations of CRF without exercise might be a low-cost alternative to applicate in the studies that involve large quantities of subjects, furthermore, it might provide a rapid diagnostic of the current status, mainly in physical education classes or before training program. However, these tools must be used carefully if the purpose is to predict more accurately VO2max in patients or athletes. 35

In the present study it was also possible to identify how BMI exerted influence on VO2max values in males (R 2 = 0.850) and females (R 2 = 0.907). This evidence was also observed in Marques-Vidal and Dias 36 , who studied children in the same age than the present study, Monyeki et al., 37 in 14-year-old adolescents, Castro-Piñeiro et al., 38 in 6- to 17-year-old children and adolescents, Arruda et al. 39 , in children and adolescents participating in a sports project, and Botelho et al., 40 in which the higher the BMI, the lower the cardiorespiratory fitness and physical fitness in general.

It should be emphasized the study of Aires et al., 41 who evaluated 11- to 18-year-old boys and girls from Portugal. The authors obtained that the students in the range of overweight and obesity had lower levels of CRF, thereby confirming a negative correlation between high fat and VO2max, furthermore reaffirming that a sedentary lifestyle is a strong predictor of heart disease.

Although cross-sectional studies and the scores of field tests show relative limitation as to its reproducibility, as highlighted in the literature, 42 they have been widely adopted as benchmarks for health-related physical fitness. Just as the Fitnessgram® tests battery, benchmarks such as Cole et al. 43 and World Health Organization (WHO) 44 play a key role, though Khadilkar et al. 13 have emphasized the possible constraints in the adoption of their cutoff points due to the anthropometric changes in population over time and the hindering of the categorization of children and adolescents.

The findings of this study were explained to the managers of the Municipal Education from the city of Aracaju, in order to alert them of the need of the development of public policy towards the adoption of regular physical activities within the school community.

In conclusion, the data of the present study showed that CRF of boys was higher than the girls and there were no differences with respect to BMI. On the other hand, the BF% of the girls showed higher levels. On both sexes there were a minimal prevalence of schoolchildren at risk of overweight and obesity, according to the criteria proposed by Fitnessgram®. Relative to CRF, a high prevalence on both sexes behaved below the area related to health. The linear regression to estimate VO2max from BMI met expectations for studies on a population scale and confirmed an inverse relationship between both variables, which highlights the need of associate the parameters of physical fitness and health for an early diagnostic of exposure to physical inactivity, obesity and other cardiovascular risk factors.

The author declare not have conflict of interest.