Independent and Combined Effects of Weight Status and Maturation on Aerobic Fitness in Adolescent School-Aged Males.

Batista, MB, Valente-dos-Santos, J, Duarte, JP, Sousa-e-Silva, P, Coelho-e-Silva, MJ, Werneck, AO, Ohara, D, Cyrino, ES, and Ronque, ERV. Independent and combined effects of weight status and maturation on aerobic fitness in adolescent school-aged males. J Strength Cond Res 34(9): 2663-2671, 2020-This study aimed to examine the independent and combined effects of pubertal and weight status on concurrent measurements of peak oxygen (V[Combining Dot Above]O2peak) in school-aged adolescent males. The final sample included 49 boys (12.3 ± 0.8 years). V[Combining Dot Above]O2peak was derived from an incremental progressive maximal protocol using a motorized treadmill. In addition, maximal oxygen uptake was estimated from a 20-m shuttle run test. Static allometric models were obtained as an alternative to performance output per unit of size descriptors. Weight status had a significant effect on V[Combining Dot Above]O2peak using simple ratio standards per unit of body mass (BM) with adolescents classified as overweight and obese (OWOB) attaining lower values of V[Combining Dot Above]O2peak. A similar trend was noted for the allometric models adopting body mass (ml·kgBM·min), stature (L·m·min), and fat-free mass (FFM; ml·kgFFM·min). Findings also suggest the influence and interaction of pubertal and weight status on absolute values of V[Combining Dot Above]O2peak. Considering the data obtained, linear equations to estimate V[Combining Dot Above]O2peak from the 20-m shuttle run test should not be applied to boys who are OWOB because it will produce inaccurate assessments of cardiorespiratory fitness and penalize those who are heavier. Equations for V[Combining Dot Above]O2peak prediction need to be specific for pubertal status and preferably consider FFM as a body size descriptor.

Tracking of health-related physical fitness between childhood and adulthood.

OBJECTIVE: The aim of the present study was to analyze the tracking of indicators of health-related physical fitness between childhood and adulthood. METHODS: The study presents a longitudinal design, with the first phase of data collection occurring annually between 2002 and 2006, and the second phase carried out in 2016. A total of 142 young adults, aged between 21 and 25 years, of both sexes participated in the study. Were evaluated body mass, stature, skinfold thickness, sit and reach test; abdominal resistance/strength test, and 20-m shuttle run test. RESULTS: The intraclass correlation coefficient (ICC) indicated that all health-related physical fitness variables presented values considered moderate to high tracking (0.37-0.67; P < 0.005) between the analyzed periods. It was verified that in all variables, tracking was higher in the female group, except for the result of the running test related to the cardiorespiratory fitness component which demonstrated greater tracking in the male group (ICC = 0.37 vs ICC = 0.50). The result of the running test for males was the only variable presenting a discrepancy in the values observed between baseline and follow-up (P < 0.05; k = 0.110). CONCLUSIONS: It was concluded that the indicators of body fat, abdominal and running tests demonstrated moderate tracking, while the sit and reach test presented high tracking.

Allometric scaling of aerobic fitness outputs in school-aged pubertal girls.

BACKGROUND: This study aimed to determine the allometric exponents for concurrent size descriptors (stature, body mass and fat-free mass) and also to examine the contribution of chronological age and pubertal status combined with above mentioned size descriptors to explain inter-individual variability in the peak of oxygen uptake (VO2peak) among girls during circumpubertal years. METHODS: The final sample included 51 girls (10.7-13.5 years). VO2peak was derived from an incremental progressive maximal protocol using a motorized treadmill. Anthropometry included body mass, stature and skinfolds. Measurements were performed by a single trained observer. Sexual maturation was assessed as self-reported stage of pubic hair (PH) development. Static allometric models were explored as an alternative to physiological output per unit of size descriptors. Allometry also considered chronological age and sexual maturation as dummy variable (PH2 vs. PH3 and PH3 vs. PH4). RESULTS: Scaling coefficients for stature, body mass and fat-free mass were 1.463 (95%CI: 0.476 to 2.449), 0.516 (95%CI: 0.367 to 0.666) and 0.723 (95%CI: 0.494 to 0.951), respectively. The inclusion of sexual maturation increased explained variance for VO2peak (55% for PH2 vs. PH3 and 47% for PH3 vs. PH4). Body mass was identified as the most prominent body size descriptor in the PH2 vs. PH3 while fat-free mass was the most relevant predictor combined with PH3 vs. PH4. CONCLUSIONS: Body mass and fat-free mass seemed to establish a non-linear relationship with VO2peak. Across puberty, inter-individual variability in VO2peak is explained by sexual maturation combined with whole body during early puberty and by sexual maturation and fat-free mass during late puberty. Additional studies need to confirm ontogenetic allometric models during years of maximal growth.

Association between risk behaviors and adiposity indicators in adolescents from Southern Brazil: A methodological approach.

The aim of this study was to analyze the association between risk behaviors and adiposity indicators in adolescents and to discuss some methodological aspects related to this relationship. We evaluated 1,321 adolescents (55.2% female) aged 10-16 years. Relative body fat (%fat) by measurement of triceps and subscapular skinfold thickness and waist circumference (WC) were used as total and central adiposity indicators, respectively. Physical inactivity, time spent in front of the TV, the consumption of soda and/or chocolate, alcohol, and tobacco smoking were analyzed as risk behaviors. Information about the socioeconomic status (categorized into three levels) and nutritional status of the mother (overweight or normal weight) were used as adjustment factors in the analyses of prevalence ratio (PR) of the outcomes and their associated 95% confidence intervals (95% CI). The chi-square test and Poisson regression were used for statistical analyses. Low associations were found between risk behaviors and adiposity indicators. Tobacco smoking was the most positively correlated behavior with adiposity in girls (%fat: PR = 1.61; 95% CI = 1.04-2.47; WC: PR = 1.90; 95% CI = 1.17-3.08) and in adolescents whose mothers were normal weight (%fat: PR = 2.31; 95% CI = 1.33-4.03; WC: PR: 2.31; CI: 1.19-4.46). Additionally, as an important methodological issue, we highlighted the assessment of risk behaviors in adolescents as crucial to producing more robust evidence on the subject. Of the investigated behaviors, we concluded that tobacco smoking is the behavior most associated with adiposity indicators.

Resting heart rate: its correlations and potential for screening metabolic dysfunctions in adolescents.

BACKGROUND: In pediatric populations, the use of resting heart rate as a health index remains unclear, mainly in epidemiological settings. The aims of this study were to analyze the impact of resting heart rate on screening dyslipidemia and high blood glucose and also to identify its significance in pediatric populations. METHODS: The sample was composed of 971 randomly selected adolescents aged 11 to 17 years (410 boys and 561 girls). Resting heart rate was measured with oscillometric devices using two types of cuffs according to the arm circumference. Biochemical parameters triglycerides, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol and glucose were measured. Body fatness, sleep, smoking, alcohol consumption and cardiorespiratory fitness were analyzed. RESULTS: Resting heart rate was positively related to higher sleep quality (ß = 0.005, p = 0.039) and negatively related to cardiorespiratory fitness (ß = -0.207, p = 0.001). The receiver operating characteristic curve indicated significant potential for resting heart rate in the screening of adolescents at increased values of fasting glucose (area under curve = 0.611 ± 0.039 [0.534 - 0.688]) and triglycerides (area under curve = 0.618 ± 0.044 [0.531 - 0.705]). CONCLUSION: High resting heart rate constitutes a significant and independent risk related to dyslipidemia and high blood glucose in pediatric populations. Sleep and cardiorespiratory fitness are two important determinants of the resting heart rate.

Validity of equations for estimating V[combining dot above]O2peak from the 20-m shuttle run test in adolescents aged 11-13 years.

The aim of this study was to analyze the validity of 4 regression equations to estimate the peak oxygen consumption (V[Combining Dot Above]O2peak) from the 20-m shuttle run test in adolescents aged 11-13 years. One hundred and fifteen adolescents, 61 boys (mean ± SD: age = 12.3 ± 0.9 years) and 54 girls (age = 12.1 ± 0.7 years) performed the 20-m shuttle run test and an incremental progressive maximal test for direct V[Combining Dot Above]O2peak analysis. Four linear regression equations were used to estimate the V[Combining Dot Above]O2peak: Barnett et al. (equation 1), Léger et al. (equation 2), Mahar et al. (equation 3), and Matsuzaka et al. (equation 4). For boys, only the V[Combining Dot Above]O2peak estimated by EQ3 did not differ from the value directly measured (p > 0.05). The EQ1, EQ2, and EQ4 underestimated the V[Combining Dot Above]O2peak, whereas the EQ3 overestimated, particularly in girls (p < 0.05). Large limits of agreement were found between the reference method and the 4 equations, with higher estimated values by EQ2 for boys (8.36 ± 15.24 mL·kg·min) and girls (2.45 ± 12.63 mL·kg·min). The highest correlation values were observed by EQ4 for boys (r = 0.80), EQ1 for girls (r = 0.72), and EQ3 for total sample (r = 0.80). The equations analyzed were not precise for individual V[Combining Dot Above]O2peak prediction; however, the EQ3 revealed better agreement, particularly for boys. Considering the data obtained in the boys and total sample, our results suggest that the EQ3 may provide the best predictive measure of V[Combining Dot Above]O2peak from the 20-m shuttle run test in adolescents aged 11-13 years.

Pressor response to fluid resuscitation in endotoxic shock: involvement of vasopressin.

OBJECTIVE: To investigate the effects of fluid resuscitation administration on vasopressin secretion and its association with pressor response in endotoxic shock during a period of inappropriately low vasopressin secretion. DESIGN: Prospective, controlled experiment. SETTING: Animal basic science laboratory. SUBJECTS: Male Wistar rats, weighing 250 to 300 grams. INTERVENTIONS: Rats received lipopolysaccharide (2 mg/kg, intravenous) and had their mean arterial pressure monitored during the next 4 hrs. Subsequently, the animals were assigned randomly to one of seven groups (n = 6 per group) that differed in the composition or volume of the resuscitation fluid administered: control group (no fluid administered); isotonic saline solution (0.9% NaCl; 4 mL/kg); hypertonic saline solution (7.5% NaCl; 4 mL/kg); 0.9% NaCl in 6% hydroxyethyl starch 450/0.7 (4, 8, or 16 mL/kg); or 7.5% NaCl in 6% hydroxyethyl starch 450/0.7 (4 mL/kg). MEASUREMENTS AND MAIN RESULTS: Blood pressure was lower in the lipopolysaccharide-treated group. Administration of 0.9% NaCl in 6% hydroxyethyl starch 450/0.7 did not change mean arterial pressure, but reduced vasopressin plasma levels at a dose of 16 mL/kg. Hypertonic saline solution or 7.5% NaCl in 6% hydroxyethyl starch 450/0.7 administration was followed by an immediate recovery of blood pressure and also by an increase in plasma vasopressin levels when compared to isotonic saline solution. The vasopressin V1 receptor antagonist (10 microg/kg, intravenous, 5 min before infusion) completely blunted the increase in mean arterial pressure induced by hypertonic saline solution or 7.5% NaCl in 6% hydroxyethyl starch 450/0.7 in endotoxemic rats. CONCLUSIONS: Isotonic blood volume expansion reduced vasopressin plasma levels. Furthermore, the subsequent release of vasopressin is essential for the pressor response caused by hypertonic fluid infusion during endotoxic shock.