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The purposes of the present study were to analyze the stability of biological risk factors for CVD (blood pressure [BP], percentage of fat mass [%FM], total cholesterol [TC]) and one behavioral/life style risk factor (physical activity [PA]), as well as to study the stability of biological risk factors clustering. The sample comprised 325 males and 367 females, aged 8-15 years old. Participants were classified as being 'at risk' according to age and sex adjusted 4th quartile or the first for PA. Three biological risk factors (%FM, SBP and TC) showed higher stability (one-year interval; r = 0.9-0.5) than DBP (r = 0.3) and PAI (r = 0.3). It can be concluded that 46% of subjects with two and/or three biological risk factors at the first measurement remained with the same number of biological risk factors in the second measurement. [ABSTRACT FROM AUTHOR]

The purpose of this study was to compare the daily activity levels of children varying in body mass over 3 consecutive weekdays. The sample was comprised of 157 children (boys, n = 64; girls, n = 93), aged 8-15 years. BMl was used as obesity indicator. Children were categorized as non-obese and overweight/obese group, according to the age-adapted values. The CSA activity monitor was used as an objective measure of daily physical activity. No significant differences were reported in the daily physical activity among boys and girls according to BMI group. Boys were significantly more engaged in moderate-to-vigorous physical activities (p = .05) than girls. Significant differences in moderate-to-vigorous physical activities (p = .05) were found between non-obese (69.3 min x day-1) and obese girls (50.7 min x day-1), while no significant differences were reported in boys. Differences between overall activities and involvement in MVPA emerged between overweight/obese and non-obese girls; therefore, obesity in girls may be linked to low levels of physical activity behavior. [ABSTRACT FROM AUTHOR]

The goal of this study was to validate an adapted version of the 'weekly checklist' in a Portuguese population. The validity was assessed by comparing self-reports against the Computer Science and Application, Inc (CSA) monitor. The sample comprised 109 children (boys, n = 42; girls, n = 67), aged 8 to 16 years old. All subjects were volunteers from local schools (porto region). The weekly activity checklist was modestly (r = 0.30) but significantly (p < .01) correlated with the CSA. Girls (r = 40; p < .01) had higher correlations than boys (0.28; p < .05). When the values were analyzed by age, excluding the young subjects (<10 years old), the correlation values were slightly higher (r = 0.38; p < .01). The Portuguese version of the 'weekly activity checklist' had similar reliability and validity as the original version. The measure appears to have lower validity in 8- and 9-year-old children. [ABSTRACT FROM AUTHOR]

Purpose: To systematically review the literature on the relationship between physical activity and the effect of physical training on brain-derived neurotrophic factor (BDNF) concentrations in children and adolescents., Methods: The searches were conducted in the databases: PubMed, ScienceDirect, Web of Science, Scopus, SPORTDiscus, Latin American and Caribbean Center for Science Information of Health, and SciELO. All original studies that analyzed the relationship between the practice of physical activity and the effect of physical training on plasma and serum BDNF concentrations in children and adolescents were included. The standardized mean difference (SMD), correlation coefficient (r), and 95% confidence interval were calculated., Results: Eleven studies were selected, totaling 1424 children and adolescents. Cross-sectional studies indicated a significant inverse relationship between physical activity and BDNF concentrations in boys (r = -.117 [-.222, -.009]; P = .033), but not in girls (P = .230). Adolescent athletes tend to have lower serum, but higher plasma BDNF concentrations than sedentary ones (SMD = -0.677 [0.188]; P < .001). An increase in serum BDNF was observed after physical training (SMD = 0.437 [0.183]; P = .017), with no effect in the control group (SMD = 0.235 [0.193]; P = .225)., Conclusions: Adolescent athletes tend to show lower serum, but higher plasma BDNF concentrations compared with sedentary individuals. Furthermore, physical training seems to increase serum BDNF concentrations in sedentary adolescents to a small extent.

Purposes: To examine the association between sedentary time (ST) and light physical activity (LPA), moderate- to vigorous-intensity physical activity (MVPA), and body mass index (BMI), and to track these behaviors over a 3-year follow-up in young schoolchildren., Methods: The final sample was 64 children (female: n = 36 or 56.3%), enrolled in schools in Porto, Portugal. Height and mass of children were measured by standard methods, and BMI was then calculated. ST, LPA, and MVPA were measured by accelerometer. Changes (Δ) and relative changes (Δ%) between 2009/2010 and 2012/2013 of ST, LPA, MVPA, and BMI were computed. Multiple linear regression analyses were fit to predict Δ%ST (outcome variable), by Δ%LPA, Δ%MVPA, and Δ%BMI (exposure variables)., Results: ST increased and LPA decreased significantly for whole sample (both Ps < .05). No statistically significant difference was found for MVPA over time. There were no differences for ΔST, ΔLPA, ΔMVPA, and ΔBMI between boys and girls. The Δ%LPA and Δ%MVPA were negatively associated with Δ%ST, whereas Δ%BMI was positively associated. Tracking coefficients varied from moderate to strong., Conclusions: Time spent in ST increases due to displacement of time in LPA. This reinforces public health measures and suggests the need for interventions focusing on offsetting the decline ST and increasing MVPA during childhood.

Purpose: This study examined the independent associations between cardiorespiratory fitness and circulating adiponectin concentration in adolescents, controlling for several potential covariates., Methods: This is a cross-sectional study in Portuguese adolescents. A sample of 529 (267 girls) aged 12-18 years were included and categorized as overweight and nonoverweight. Cardiorespiratory fitness was assessed by 20 meters shuttle run test. We measured serum adiponectin, high-sensitivity C-reactive protein, fasting glucose, insulin and HDL-cholesterol., Results: After adjustment for age, sex, pubertal stage, adherence to the Mediterranean diet, socioeconomic status, body fat percentage, insulin resistance, HDL-cholesterol and C-reactive protein, regression analysis showed a significant inverse association between adiponectin and cardiorespiratory fitness in nonoverweight participants (B=-0.359; p < .042). Analysis of covariance showed a significant difference between the highest cardiorespiratory fitness Healthy zone (above healthy zone) and the Under and the Healthy cardiorespiratory fitness zones in nonoverweight adolescents (p = .03) (F (2, 339) = 3.156, p < .001)., Conclusion: Paradoxically, serum adiponectin levels are inversely associated with cardiorespiratory fitness in nonoverweight, but not in overweight adolescents. In nonoverweight adolescents, those with highest levels of cardiorespiratory fitness (above healthy zone) presented lower levels of adiponectin compared with those in Under and Healthy cardiorespiratory fitness zones.

Purpose: Weight status-referenced pedometer step-count guidelines for young people have been developed for populations from high-income countries and may not be applicable to middle- and low-income countries. The objectives of this study were 1) to develop cut-off points for pedometer-determined step count in young Brazilians using waist circumference (WC) as a reference criterion, and 2) to analyze the capacity of previous recommendations to discriminate abdominal obesity in the sample studied., Methods: A cross-sectional study was conducted on 1,044 schoolchildren (456 boys) aged 6-17 years from Northeastern Brazil. WC was measured and daily step counts were determined with a pedometer., Results: The area under the curve (AUC) of step count was significant for boys (AUC = 0.55; 95%CI: 0.50-0.59) and girls (AUC = 0.57; 95%CI: 0.53-0.61). Our cut-off points (14,414 and 11,355 steps for boys and girls, respectively) were more balanced in terms of sensitivity and specificity compared with previous recommendations. The use of previous guidelines to classify step count in the sample provided very low sensitivity or specificity and wide variation in the prevalence of insufficient physical activity (39.3-77.0%)., Conclusions: A universal step-count recommendation for young people may not be adequate and specific guidelines seem to be necessary for different countries or regions.

Purpose: There are few reliable studies assessing the effect of physical exercise (PE) on adipokines levels at young ages. Our objective was to study the effects of regular PE on plasma adipokines in pediatric overweight and obesity., Method: 117 overweight and obese children and adolescents (47% females; 10.2 years) participated in an 8-month longitudinal study divided in two groups: PE group (n = 80), engaged in an after-school PE program; control group (n = 37), with no PE program. Plasma lipids, C-reactive protein (CRP), adiponectin, resistin, leptin, IL-6, IL-1beta, TNF-alpha, insulin and glucose levels were determined., Results: contrarily to the control group, the PE group presented reductions in body mass index z-score (BMIzsc) and body fat percentage that were accompanied by an improvement in lipid profile and insulin resistance, a reduction in CRP and TNF-alpha and an increase in adiponectin levels. The reductions in BMIzsc were inversely correlated with changes in adiponectin (r=-0.329, p = .003) and positively correlated with changes in percentage body fat (r = .262, p = .032), triglycerides (r = .228, p = .042) and leptin (r = .285, p = .010)., Conclusions: Moderate reductions in adiposity improve proinflammatory status in obese children and adolescents. A more substantial reduction in BMIzsc was associated with a greater increment in adiponectin and reduction in leptin.

Social support (SS) from parents and peers are key reinforcing factors in the Youth Physical Activity Promotion (YPAP) model. This study aims to identify the relative contribution of parental and peer SS on youth participation in moderate to vigorous physical activity (MVPA). Participants included 203 high school students (n = 125 girls; mean age 14.99 ± 1.55 years). MVPA was assessed by accelerometry. SS influences were evaluated using a well-established scale. Structural equation modeling measured (AMOS, Version 19) the relative fit of the YPAP models using both parental and peer SS. Parental SS had significant associations with both predisposing factors, enjoyment (β = .62, p < .01), and self-efficacy (β= .32, p < .01), as well a direct effect on MVPA (β = .30, p < .01). Peer SS had direct effect on MVPA (β = .33, p < .05), also significantly influenced levels of enjoyment (β = .47, p < .01) and self-efficacy (β = .67, p < .01). In both models self-efficacy mediated the influence on MVPA. The direct effects for parents and peers were similar. This demonstrates that both parental and peer social support exert a strong influence on adolescent MVPA.

Unlabelled: Nonalcoholic fatty liver disease (NAFLD) is one of the most frequent complications associated with excess adiposity. Its pathogenesis is complex and there are multiple factors that may contribute to it., Aim: To analyze whether cardiorespiratory fitness (CRF), waist circumference (WC), and C-reactive protein (CRP) are associated with alanine aminotransferase (ALT) in children with obesity., Methods: 79 overweight/obese children of both genders, 11-13 year-olds, with abnormal serum ALT from Porto public schools comprised the sample. Measurements included CRF (20-m Shuttle Run Test), WC (NHANES protocol), CRP and ALT (Cholestech LDX analyzer). Logistic regression adjusted for gender, maturation, and weight with ALT levels as dependent variable (risk vs. non risk), and WC (risk vs. non risk), CRP (risk vs. non risk), and CRF (fit vs. unfit) as independent variables. Level of significance was set at 95%., Results: Logistic regression showed that obese fit children were less likely to have abnormal ALT values (OR=.031), Conclusion: In obese children, higher cardiovascular fitness appears to reduce the chance of decreased liver function.

The purpose of this study was to calculate and validate reference standards for the 20-m shuttle run test (SR) in youths aged 10-18 years. Reference standards based on the number of completed SR laps were calculated by LMS method in a reference group of 5559 students. Cut-off values for SR laps were determined and tested by ROC curve analysis in a validation group (633 students), from which waist circumference, HDL-cholesterol, triglycerides, fasting glucose and mean arterial pressure were assessed to calculate a metabolic risk score, later dichotomized in low and high metabolic risk (HMRS). The accuracy of SR laps standards was significant for girls (AUC = 0.66; 95% CI = 0.58-0.74; p < .001) and boys (AUC = 0.71; 95% CI = 0.62-0.79; p < .001) for identifying subjects at HMRS. The 40th percentile was the best cut-off for SR laps in girls (SENS = 0.569; 1-SPEC = 0.330) and boys (SENS = 0.634; 1-SPEC = 0.266). New SR laps reference standards are able to discriminate metabolic risk levels, and may provide a valuable tool for early prevention of cardiovascular risk factors.

Sex differences in physical activity (PA) through pubertal maturation and the growth spurt are often attributed to changing interests. The contribution of sex differences in biological maturation to the adolescent decline has received limited attention. This study examined the contribution of somatic maturation to sex differences in objective assessments of sedentary behavior and PA in Portuguese adolescents (N = 302, aged 13-16 years). Maturation was estimated from the percentage of predicted mature stature and physically active and inactive behaviors assessed with Actigraph GT1M accelerometers. The influence of age, sex and their interaction on body size, maturation and physical behaviors were examined using factorial ANOVA and, subsequently, ANCOVA (controlling for maturation) tested the effect of sex. Males spent more time in MVPA and less time in sedentary behavior than females. However, sex differences were attenuated when maturation was controlled; thus suggesting that maturity may play an important role in adolescent behaviors.

The aim of this study was twofold (1), to examine the prospective relationship of baseline TV viewing with BMI and CRF both at baseline and over a 2-year period, and (2) to examine the prospective relationship of baseline TV viewing and changes (Delta) on BMI and CRF over a 2-year period. Data were collected in a sample of 135 (64 girls) rural children ages 7 yr-old from elementary schools in Fundão, Portugal. Obesity status was obtained by the age-sex specific BMI cut points and CRF by a 9 min run test. TV viewing was also analyzed and children were assigned as one of two groups: the low TV watching (LTV), and high TV watching (HTV), users based upon them reported to spend less or more than 2 h/day watching TV, respectively. Logistic regression showed that those who were assigned to HTV group were 2.4 times (OR= 2.48; p = .04) more likely to be classified as unfit at time 1. Further the data showed that the LTV were more likely (OR= 0.36; p = .02) to be classified in high DeltaCRF change over time. The findings of this study suggest that there was a significant inverse association between times spent watching TV and CRF but not BMI over a 2-yr period.

The purpose of this study was twofold: first to document the gender differences in Moderate to Vigorous Physical Activity (MVPA) according to two epoch systems (5 vs. 60 s) in preschoolers, and, second to document the differences in physical activity (PA) patterns according to two different epoch choices. The sample comprised 59 preschoolers (31 girls) aged 2-5 years old. PA was assessed by accelerometer during school hours. The time spent in MVPA was significantly higher (p < .001) when a 5-s epoch was considered compared to the 60-s epoch, regardless gender. Further, it was found a difference of ?17 min difference between the 2 epoch systems for MVPA. Different epoch times might affect the time spent in MVPA among preschool children.

Specific behavior context such as type of PA (organized vs. nonorganized) might be associated with different environmental correlates. The main goal of this cross-sectional survey was to examine perceived environmental associations with type of adolescents' physical activity (PA) choices (organized and nonorganized). A sample of this study comprised 425 girls with mean age of 14.5 years-old. Environmental variables and PA were assessed by questionnaire, which allowed to define the type (organized or nonorganized) of PA. No associations were found between environmental perceptions and the participation in organized activities. However, different dimensions of environmental variables such as accessibilities to facilities (p -/+ .05) aesthetics (p -/+ .05) and social environment (p -/+ .05) were associated to girls' PA participation in nonorganized activities (NOPA). Our findings suggested that some environmental characteristics might play an important role in girls' NOPA participation.

This study analyzes trends in CVD risk factors and aerobic performance. Two cross-sectional studies were performed including 138 (58 boys and 80 girls) in 1998 and 110 (44 boys and 66 girls) in 2003 adolescents. Although in cardiorespiratory fitness (CRF) boys performed better than girls, they had lower body mass index (BMI) and total cholesterol (TC) than girls. The data also showed a significant year effect (p = .000) for CRF in both boys and girls. The sex-age group interaction was not significant (p > .05). This cross-sectional study revealed a marked low CRF level over time in both boys and girls.

This study analyzes the relationships between leisure time physical activity (LTPA), sedentary behaviors, socioeconomic status, and perceived environmental variables. The sample comprised 815 girls and 746 boys. In girls, non-LTPA participants reported significantly more screen time. Girls with safety concerns were more likely to be in the non-LTPA group (OR = 0.60) and those who agreed with the importance of aesthetics were more likely to be in the active-LTPA group (OR = 1.59). In girls, an increase of 1 hr of TV watching was a significant predictor of non-LTPA (OR = 0.38). LTPA for girls, but not for boys, seems to be influenced by certain modifiable factors of the built environment, as well as by time watching TV.