Aptidão cardiorrespiratória de escolares adolescentes do sistema público de ensino

Abstract

Cardiorespiratory fitness is one of the components of physical fitness related to health, being considered a relevant indicator of health status. Its low levels can increase the risk for development of cardiovascular diseases and metabolic syndrome, besides being a reality observed in international and national scenario. This research is aimed to investigate direct and indirect association of variables age, fat percentage, abdominal muscle resistance and average arterial pressure with cardiorespiratory fitness of adolescent students. This is an epidemiological, cross-sectional and analytical study. The population consisted of school adolescents from municipal public school system in the city of Montes Claros, MG, enrolled between sixth and ninth year in 2017. Data collection was carried out in the second semester of 2017 in thirteen schools. It was used a questionnaire for data collection that included sociodemographic (sex and age) and scholarity characteristics (school year). For anthropometric evaluation, weight, height and skin fold measurement were measured. Systemic blood pressure, abdominal muscle resistance, through the sit up test (number of abdominals in one minute), and cardiorespiratory fitness, through the six-minute running test. In data analysis, categorical variables were described through their distribution of absolute and relative frequencies, and numerical variables by mean, median, standard deviation, minimum and maximum values, asymmetry coefficients (sk) and kurtosis (ku), corrected by the drawing effect. To evaluate direct and indirect effects of variables on cardiorespiratory fitness, it was used a multivariate model adapted by the path analysis technique. Direct and indirect effects represented by standardized coefficients were estimated, with statistical significance and evaluated by the Critical Ratio (CR) at 5% significance level. 860 schoolchildren participated in the research, 52.9% of female sex, with a mean age of 12.7 years (SD = ± 0.97). Regarding education, 63% were in sixth or seventh year. It was evidenced the direct negative effect of girls' age (β = -0.08; p = 0.016) and fat percentage (girls: β = -0.63; p <0.001; boys β = -0.59; p <0.001) on cardiorespiratory fitness, in addition to the direct and positive effect of abdominal resistance (girls: β = 0.10; p = 0.005; boys: β = 0.09; p = 0.019) in both sexes. The indirect way which was highlighted was the effect of percentage of fat on cardiorespiratory fitness mediated by abdominal resistance (girls: β = - 0.02; boys: β = -0.01). The proportion of direct effect in relation to total effect of percentage of fat on cardiorespiratory fitness was 95.4% in girls and 96.7% in boys (not mediated by other variables). Considering the effect of age, fat percentage and muscle resistance on cardiorespiratory fitness, it is suggested to promote actions that encourage practice of physical exercises from earlier ages.