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Background: Little is known on how the substitution of time spent in sedentary behavior (SB) patterns with time spent in physical activity impacts cardiovascular risk factors during adolescence. The study aimed to investigate how the substitution of time spent in SB and sedentary bouts with time spent in different physical activity intensities was associated with longitudinal changes in cardiovascular risk factors in analyses stratified by sex. Methods: This is a prospective cohort study with a mean follow-up period of 3.2 (±0.34) years, involving 109 (60 girls and 49 boys) Brazilian adolescents. Body mass index, waist circumference, and cardiorespiratory fitness were the cardiovascular risk factors considered. A cardiovascular risk score was calculated. Sedentary bouts, light physical activity (LPA), and moderate to vigorous physical activity (MVPA) were measured by accelerometers. Multivariate linear regression models adopting the isotemporal substitution were used to analyze the association between substitution of 10 minutes per day of sedentary bouts with LPA and MVPA and risk factors. All analyses considered 5% significance levels. Results: Substitutions of SB, short and long bouts, with MVPA were associated with higher cardiorespiratory fitness in boys (β = 0.077; 95% confidence interval, 0.001 to 0.55; β = 0.076; 95% confidence interval, 0.003 to 0.154; and β = 0.084; 95% confidence interval, 0.001 to 0.167, respectively). No associations were observed when analyses involved substitution of sedentary bouts with LPA, adiposity, cardiovascular risk score, and girls. Conclusions: Substituting SB bouts with MVPA appears to favorably influence changes of cardiorespiratory fitness in boys during adolescence. Greater benefits appear to occur when longer sedentary bouts are substituted by MVPA. [ABSTRACT FROM AUTHOR]

Background: Recent statistical approaches have allowed consideration of the integrated relationships between sedentary behavior (SB) and physical activity (PA) with different health outcomes. The present paper aimed to systematically review the literature and synthesize evidence about associations between hypothetical reallocations from SB to different PA intensities and cardiovascular risk factors in youth. Methods: A systematic search of 8 databases was performed. Observational studies with a population of children and/or adolescents and based on statistical analysis that investigated the associations between time reallocations from SB to PA and cardiovascular risk factors were included. Results: Twenty-eight studies met the inclusion criteria. Level of evidence (derived from cross-sectional studies) indicated that the reallocation from SB to moderate to vigorous PA was beneficially associated with adiposity, cardiorespiratory fitness, and cardiometabolic biomarkers in youth. Reallocation from SB to light PA was not associated with the analyzed outcomes. Associations derived from longitudinal studies were mostly inconclusive. Conclusion: Cardiovascular risk factors could be improved by increasing moderate to vigorous PA at the expense of time spent in SB in pediatric populations. Prospective studies or studies investigating the effects of reallocating sedentary bouts to PA are needed. [ABSTRACT FROM AUTHOR]

Purpose: Compare tracking groups with cognitive control functions and plasma brain-derived neurotrophic factors concentrations from childhood to adolescence. Methods: This is a prospective study with 3 years of follow-up. At baseline, data from 394 individuals were collected (11.7 y), and data were obtained from 134 adolescents (14.9 y) at the 3-year follow-up. At both time points, anthropometric and maximal oxygen uptake data were collected. Cardiorespiratory fitness (CRF) groups were classified into high or low CRF. At follow-up, cognitive outcomes were collected via the Stroop and Corsi block test; plasma brain-derived neurotrophic factors concentrations were also analyzed. Results: Comparisons demonstrated that maintaining high CRF over 3 years results in shorter reaction time, better inhibitory control, and higher working memory values. Likewise, the group that moved from low to high CRF over 3 years presented better reaction time. Plasma brain-derived neurotrophic factors concentrations were higher for the group that increased its CRF over the 3 years in relation to the low–low group (90.58 pg·mL−1; P =.004). However, after scaling by an allometric approach, differences were only found for reaction time and working memory between high–high and high–low groups. Conclusion: Maintaining high CRF over 3 years was positively related to reaction time and working memory in relation to adolescents that decreased their levels of CRF. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the association between patterns of sedentary behavior and obesity indicators among adolescents. Methods: This was a cross-sectional study conducted among 389 adolescents (186 boys) aged 10–14 years. Body mass index, body fat (skinfolds), and waist circumference were adopted as outcomes. Sedentary behavior patterns (total time, bouts, and breaks) measured through accelerometry (GT3X and GT3X+; ActiGraph, Pensacola, FL) were adopted as exposures. Peak height velocity, moderate to vigorous physical activity (accelerometer), cardiorespiratory fitness (Léger test), sex, and chronological age were adopted as covariates. Linear regression models adjusted for covariates were used to determine associations between outcome and exposure variables. Results: The mean age of adolescents was 11.8 (0.7) years. Boys were more active than girls (P <.001). Accumulating shorter bouts (1–4 min) of sedentary behavior was negatively associated with body mass index (β = −0.050; 95% confidence interval [CI], −0.098 to −0.003) and waist circumference (β = −0.133; 95% CI, −0.237 to −0.028). Similarly, a higher number of breaks in sedentary behavior were negatively associated with body mass index (β = −0.160; 95% CI, −0.319 to −0.001) and waist circumference (β = −0.412; 95% CI, −0.761 to −0.064). Conclusion: Shorter bouts of sedentary behavior (1–4 min) and a higher number of breaks of sedentary behavior were associated with lower adiposity. Our findings also suggest that breaking up sedentary time to ensure bouts of sedentary behavior are short might contribute to the prevention of obesity in adolescents. [ABSTRACT FROM AUTHOR]

Purpose: To analyze the relationship between engagement in sports in early life and bone variables among adults of both sexes. Methods: The sample was composed of 225 men and women. Demographic data were collected, and dual-energy X-ray absorptiometry was used to assess bone mineral density, bone mineral content, and lean soft tissue. Sports participation in early life was assessed by an interview including childhood and adolescence. Consumption of tobacco and alcohol was also assessed by interview and the habitual physical activity level by a pedometer. Results: Inactive men had bone mineral content around 11% lower than active men in childhood or adolescence, whereas for women, this difference represented around 14%. Active men had 74% less fat mass than inactive men in early life, and the difference was 67% for women. Early sports participation explained the differences in whole-body bone mineral content (16.8%, P-value = .005) and bone mineral density (8.8%, P-value = .015), as well as bone mineral density in lower limbs (18.9%, P-value = .001) among women. Conclusion: Adults engaged in sports in early life have higher bone mass than their inactive peers, especially women. [ABSTRACT FROM AUTHOR]