Background: The purpose of this study was to analyze the relation between body mass index (BMI), Cardiorespiratory Fitness (CRF), and levels of physical activity (PA) from sedentary to very vigorous intensities, measured by accelerometry, in students from a middle and high school.Methods: This cross-sectional study included 111 children and adolescents, age 11 to 18 years. PA was assessed with an accelerometer for 7 consecutive days (1 minute epoch) using specific cut-points. PA components were derived using special written software (MAHUffe). CRF was assessed by maximal multistage 20m shuttle run. T-test was used to test differences between BMI groups, Pearson’s correlation, to analyze correlations between all variables and multinomial logistic regression, and to predict the value of BMI categories.Results: This paper provides evidence that BMI was inversely and significantly correlated with CRF. Only CRF was correlated with Vigorous and Very Vigorous PA levels and total amount of PA. Children with Overweight/Obesity were less likely to perform more laps than normal weight counterparts. The total amount or intensity level of PA did not show any influence on BMI level.Conclusions: Low CRF is strongly associated with obesity, which highlights the importance of increasing CRF for a protective effect even in youth. No associations were found for PA and BMI.

The purpose of this study was to analyse the associations between sports participation, levels of moderate to vigorous physical activity (MVPA) and cardiorespiratory fitness (CRF). The study comprised 310 participants (183 girls and 127 boys) aged 11–18 years. Sports participation was assessed by questionnaire and habitual physical activity (PA) was measured objectively with accelerometers. The 20-m shuttle-run test was used to estimate CRF. Logistic regression analyses were carried out with CRF as the outcome. The odds ratio (OR) for being fit was greater for those who comply with 60 min · day⁻¹ in MVPA (OR = 2.612; 95%confidence interval [CI] = 1.614–4.225) in comparison with those who do not. Participation in competitive sports at club levels increased the chances of being fit (OR = 13.483; 95%CI = 4.560–39.864), independently of MVPA levels. There were positive and significant trends in CRF and objectively measured PA across the levels of engagement in competitive sports (P < 0.05). Concluding, participation in competitive sports at club level is more effective than other organised or non-organised sports to reach healthier levels of CRF and recommend levels of MVPA.

Background: The objective of this study was to analyze associations of cardiorespiratory fitness (CRF) with physical activity, time spent watching television and using computer, mode of commuting to school (CS), and adiposity, by gender.Methods: Participants were 1708 students (53.8% girls), aged 11 to 19 years. CRF was evaluated with a 20-meter shuttle-run test using VO₂max by previously published equation. Maturation stages determined by Tanner’s criteria, body mass index, and skinfolds were measured, and a questionnaire used to assess socioeconomic status, PA, television and computer time, and mode of CS. We conducted a regression analysis using CRF as the dependent variable.Results: CRF was independent and positively associated with physical activity [β = 0.338 (95% CI = 0.119; 0.188); P < .001] and with maturation [β = −0.876 (95% CI = 0.666; 1.087); P < .001]; independent and negatively associated with television time [β = −0.003 (95% CI = −0.005; −0.002); P < .001] and adiposity [β = −0.068 (95% CI = −0.076; −0.060); P < .001]. CRF was positively associated with CS [β = 0.337; (95% CI = 0.014; 0.741); P = .014]. No associations were found for computer time.Conclusions: These findings suggest that increasing overall physical activity levels through interventions in different domains such as active CS, reducing sedentary activities, such as television time, might be effective strategies for improving CRF in youth.

Background: Elevated blood pressure (BP) has been reported in young people and seems to be associated with body mass index (BMI) and reduced physical activity (PA). Aim: This study sought to analyse the association of BP with BMI, PA intensity patterns and cardiorespiratory fitness (CRF) in youth. Subjects and methods: A cross-sectional study was carried out including 66 boys (13.91±1.76) and 97 girls (14.02±1.71). Anthropometric characteristics, CRF and BP were assessed during school time and accelerometers were utilized to determine intensity of PA. Results: The linear regression model, adjusted for age, sex and height, showed that higher values of BMI were associated (p≤0.05) with higher values of systolic blood pressure (SBP) (1.39; 95% CI: 0.56; 2.23) and diastolic blood pressure (DBP) (1.52; 95% CI: 0.68; 2.37). Additionally, SBP, but not DBP, was inversely associated (p≤0.05) with moderate PA (−0.25; 95% CI: −0.47; −0.02) and positively correlated with sedentary activities (0.04; 95% CI: 0.00; 0.08). Conclusion: The present study showed that BMI and time spent in sedentary activities were inversely associated with SBP. However, time spent in moderate PA was positively associated with SBP. BMI was the single predictor of DBP.

The aim of this study was to analyse whether Physical Activity Index (PAI), Physical Fitness, Screen Time (watching TV and computer use), Socio-economic Status and Commuting to School made a significant contribution to longitudinal changes in Body Mass Index (BMI) in youth. This longitudinal study was carried out over a period of 3 years with 345 students (147 boys) who were between 11 and 16 years old at the beginning of the study. Students were invited to perform tests from FITNESSGRAM Battery for Curl-Ups, Push-Ups, Back-Saver Sit and Reach, and 20 m Shuttle-Run (CRF). Fitness tests were categorized in “Healthy Zone” (HZ) and “Under Healthy Zone” (UHZ), PAI in “less active” and “active”; Socio-economic Status, in low, middle and high education level, and Commuting in active and passive. BMI was corrected for age and gender meaning that we subtracted the age-and-sex-specific cut points for overweight. Corrected body mass index was used as dependent variable in a Linear Mixed Model. The main result was the strong positive and independent association of individuals with CRF performances UHZ with corrected body mass index. In conclusion, the results of this longitudinal study showed markedly an important relationship of lower fitness levels with the risk of being overweight/obese, in particular CRF and abdominal strength.