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This work presents a semi-analytical method for laminar steady-state channel and pipe flows of viscoelastic fluids using the Linear Phan-Thien-Tanner (LPTT) constitutive equation, with solvent viscosity contribution. For the semi-analytical method validation, it compares its results and two analytical solutions: the Oldroyd-B model and the simplified LPTT model (without solvent viscosity contribution). The results adopted different values of the dimensionless parameters, showing their influence on the viscoelastic fluid flow. The results include the distribution of the streamwise velocity component and the extra-stress tensor components in the wall-normal direction. In order to investigate the proposed semi-analytical method, different solutions were obtained, both for channel and pipe flows, considering different values of Reynolds number, solvent viscosity contribution in the homogeneous mixture, elongational parameter, shear parameter, and Weissenberg number. The results show that the proposed semi-analytical method can find a laminar solution using the non-Newtonian LPTT model with solvent viscosity contribution and verify the effect of the parameters in the resulting flow field.
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Introduction: To a considerable extent, the magnitude of blood volume (BV) and hemoglobin mass (Hbmass) contribute to the maximum O2-uptake (VO2max), especially in endurance-trained athletes. However, the development of Hbmass and BV and their relationships with VO2max during childhood are unknown. The aim of the present cross-sectional study was to investigate Hbmass and BV and their relationships with VO2max in children and adolescents. In addition, the possible influence of endurance training and chronic hypoxia was evaluated. Methods: A total of 475 differently trained children and adolescents (girls n = 217, boys n = 258; untrained n = 171, endurance trained n = 304) living at two different altitudes (â¼1,000 m, n = 204, â¼2,600 m, n = 271) and 9-18 years old participated in the study. The stage of puberty was determined according to Tanner; Hbmass and BV were determined by CO rebreathing; and VO2max was determined by cycle ergometry and for runners on the treadmill. Results: Before puberty, there was no association between training status and Hbmass or BV. During and after puberty, we found 7-10% higher values in the trained groups. Living at a moderate altitude had a uniformly positive effect of â¼7% on Hbmass in all groups and no effect on BV. The VO2max before, during and after puberty was strongly associated with training (pre/early puberty: boys +27%, girls +26%; mid puberty: +42% and +45%; late puberty: +43% and +47%) but not with altitude. The associated effects of training in the pre/early pubertal groups were independent of Hbmass and BV, while in the mid- and late pubertal groups, 25% of the training effect could be attributed to the elevated Hbmass. Conclusions: The associated effects of training on Hbmass and BV, resulting in increased VO2max, can only be observed after the onset of puberty.
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NEW FINDINGS: What is the central question of this study? To what extent does testosterone influence haemoglobin formation during male puberty? What is the main finding and its importance? In boys, testosterone might be responsible for about 65% of the increase in haemoglobin mass during puberty. The underlying mechanisms are assumed to be twofold: (i) indirectly, mediated by the increase in lean body mass, and (ii) directly by immediate testosterone effects on erythropoiesis. Thereby, an increase in testosterone of 1 ng/ml is associated with an increase in haemoglobin mass of â¼65 g. These processes are likely to determine endurance performance in adulthood. ABSTRACT: The amount of haemoglobin during puberty is related to endurance performance in adulthood. During male puberty, testosterone stimulates erythropoiesis and could therefore be used as a marker for later endurance performance. This cross-sectional study aimed to determine the relationship between serum testosterone concentration and haemoglobin mass (Hbmass) in both male and female children and adolescents and to evaluate the possible influences of altitude and training. Three-hundred and thirteen differentially trained boys and girls aged from 9 to 18 years and living at altitudes of 1000 and 2600 m above sea level entered the study. The stage of sexual maturation was determined according to the classification of Tanner. Testosterone was measured by ELISA. Hbmass was determined by CO-rebreathing. Haemoglobin concentration did not change during maturation in girls and was 11% higher during puberty in boys, while Hbmass was elevated by 33% in Tanner stage V compared to stage II in girls (498 ± 77 vs. 373 ± 88 g) and by 95% in boys (832 ± 143 vs. 428 ± 95 g). This difference can most likely be attributed to indirect testosterone influences through an increase in lean body mass (LBM) and to direct testosterone effects on erythropoiesis, which increase the Hbmass by â¼65 g per 1 ng/ml. Altitude and training statuses were not associated with testosterone, but with an increase in Hbmass (altitude by 1.1 g/kg LBM, training by 0.8 g/kg LBM). Changes in Hbmass are closely related to testosterone levels during male puberty. Further studies will show whether testosterone and Hbmass during childhood and adolescence can be used as diagnostic tools for endurance talents.
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Eritropoese , Testosterona , Adolescente , Adulto , Composição Corporal , Criança , Estudos Transversais , Feminino , Humanos , Masculino , PuberdadeRESUMO
Alterations in pubertal timing have been associated with long-term health outcomes. While a few reports have shown that dietary intake of selenium is associated with fertility and testosterone levels in men, no human studies have considered the association between selenium and pubertal development in children. We examined the cross-sectional association of childhood dietary intake of selenium with pubertal development among 274 girls and 245 boys aged 10-18 years in Mexico City. Multiple logistic and ordinal regression models were used to capture the association between energy-adjusted selenium intake (below Recommended Dietary Allowance (RDA) vs. above RDA) and stages of sexual maturity in children, adjusted for covariates. We found that boys with consumption of selenium below the RDA had lower odds of a higher stage for pubic hair growth (odds ratio (OR) = 0.51, 95% confidence interval (95% CI): 0.27-0.97) and genital development (OR = 0.53, 95% CI: 0.28-0.99) as well as a lower probability of having matured testicular volume (OR = 0.37, 95% CI: 0.15-0.88) compared with boys who had adequate daily dietary intake of selenium (above RDA). No associations were found in girls. According to our results, it is possible that inadequate consumption of selenium may be associated with later pubertal development in boys, suggesting a sex-specific pattern. Future work with a larger sample size and measures of selenium biomarkers is needed to confirm our findings and improve understanding of the role of this mineral in children's sexual development.
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Dieta , Puberdade/efeitos dos fármacos , Puberdade/fisiologia , Selênio/administração & dosagem , Maturidade Sexual/efeitos dos fármacos , Adolescente , Criança , Estudos Transversais , Feminino , Humanos , Masculino , México , Recomendações Nutricionais , Selênio/deficiência , Fatores Sexuais , Maturidade Sexual/fisiologiaRESUMO
The present study aims: (1) to explore the influence of lean mass (LM) on bone mineral content (BMC), (2) to investigate the pubertal influences on the BMC-LM relation, and (3) to perform Z-score charts of BMC-LM relation, stratified by gender and reproductive status categorized by age ranges. A cross-sectional analysis was conducted using 4001 healthy subjects between 7 and 90 years participating in the Health Workers Cohort Study. Of these, 720 participants were ≤ 19 years, 2417 were women ≥ 20 years, and 864 were men ≥ 20 years. Using Dual X-ray absorptiometry (DXA), we measured BMC and LM. Participants' pubertal development was assessed according to Tanner's stage scale. To describe BMC-LM relation, simple correlation coefficients were computed. To produce best-fit equations, an ANOVA test was conducted. Z-score graphs for the BMC-LM relation were obtained. In general, the BMC-LM correlations were linear and highly significant. For boys, curves were virtually parallel, with similar intercepts and a progressive displacement of values toward the upper-right region of the graph, for each Tanner subgroup. For girls, curves for Tanner 1-2 and 4-5 stages were parallel; but, in girls Tanner 4-5, the intercepts were significantly higher by about +300-400 g of BMC (P < 0.001). For postmenopausal women, the curve was parallel to that for the premenopausal but showed a lower intercept (P < 0.001). We provide DXA reference data on a well-characterized cohort of 4001 healthy subjects. These reference curves provide a reference value for the assessment and monitoring of bone health in all age groups included in the present study.
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Peso Corporal , Densidade Óssea , Reprodução , Caracteres Sexuais , Magreza/fisiopatologia , Adolescente , Adulto , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Composição Corporal , Criança , Estudos de Coortes , Estudos Transversais , Feminino , Pessoal de Saúde , Humanos , Masculino , Pessoa de Meia-Idade , Valores de Referência , Adulto JovemRESUMO
BACKGROUND: Studies examining the association of anogenital distance (AGD), a biomarker of prenatal androgen exposure, with sexual development in children are lacking. OBJECTIVE: To assess the association between AGD measures and reproductive outcomes, including puberty onset, testicular volume, reproductive hormone levels, and urogenital malformations in boys aged 9-11 years. MATERIALS AND METHODS: A cross-sectional study was conducted among children belonging to the Spanish Environment and Childhood (INMA) Project, a population-based birth cohort study. The present sample included 279 boys for whom data were available on AGD, pubertal stage, testicular volume, and relevant covariates. Out of the boys with AGD data, 187 provided a blood sample for hormone analysis. AGD was measured from the center of the anus to the base of the scrotum. Pubertal development was assessed according to Tanner stage of genital development (G1-G5), and testicular volume was measured with an orchidometer. RESULTS: After adjusting for potential confounders, logistic regression analysis showed that AGD was positively associated with testicular volume but not with Tanner stage (>G1 vs. G1), serum hormone levels, or undescended testis. Regardless of their age, body mass index, and Tanner stage (G1 or >G1), boys with longer AGD showed increased odds of a testicular volume >3 mL (OR = 1.06, 95%CI = 1.00-1.19 per 10% increment in AGD; and OR = 3.14, 95%CI = 0.99-9.94 for AGD >42 mm vs. <33 mm). DISCUSSION: Longer AGD was associated with testicular growth, an indicator of gonadarche, but not with other reproductive outcomes. CONCLUSIONS: Although AGD was positively associated with testicular volume, it remains unclear whether AGD predicts testis size at puberty or is related to puberty onset.
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Canal Anal/anatomia & histologia , Desenvolvimento Infantil , Puberdade , Escroto/anatomia & histologia , Testículo/anatomia & histologia , Fatores Etários , Biomarcadores/sangue , Criança , Estudos Transversais , Criptorquidismo/sangue , Criptorquidismo/diagnóstico , Criptorquidismo/epidemiologia , Hormônios/sangue , Humanos , Hipospadia/sangue , Hipospadia/diagnóstico , Hipospadia/epidemiologia , Masculino , Tamanho do Órgão , Valor Preditivo dos Testes , Puberdade/sangue , Fatores de Risco , Espanha/epidemiologiaRESUMO
OBJECTIVE: To evaluate the extent to which pubertal timing alters the classification of extremes of attained stature across race-ethnicity groups of youths in the US. STUDY DESIGN: We performed analyses of height and Tanner staging data of 3206 cross-sectional national sample of youths ages 8-18 years (53% male, n = 1606), 72% of whom were non-Hispanic white, 9% Mexican American, and 19% non-Hispanic black . Specialized growth models were used to derive Tanner-stage-age-adjusted z scores (TSAHAZ). The prevalence of shortness (<-1SD) and tallness (≥+1SD) status was quantified using TSAHAZ. RESULTS: Highly variable patterns of prevalence of shortness and tallness via chronologic age height z score (CAHAZ) were observed in results stratified by race-ethnicity and sex. Tallness CAHAZ prevalence was high among non-Hispanic white and non-Hispanic black male youths relative to Mexican American (40.0%-43.3% vs 20.5%) with a similar pattern in female youths. In both sexes, this pattern was eliminated with TSAHAZ, with Mexican American youth becoming statistically not different from their non-Hispanic white and non-Hispanic black peers. CONCLUSIONS: Differences in timing of puberty between race-ethnicity groups affects estimated prevalence of shortness and tallness of attained height that remains uncaptured with CAHAZ. Adjustment for pubertal development might help isolate crucial determinants of attained stature and other aspects of body composition that may be most responsive to intervention programs in populations. The curves developed by adjusting for pubertal status may help the clinician avoid misclassification of children with early and late pubertal development.
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Estatura , Puberdade , Grupos Raciais/estatística & dados numéricos , Adolescente , Criança , Feminino , Inquéritos Epidemiológicos , Humanos , Masculino , Modelos Estatísticos , Estudos de Amostragem , Estados Unidos/epidemiologiaRESUMO
OBJECTIVES: To compare the responses of high-sensitivity cardiac troponin T (hs-cTnT) and NH2-terminal probrain natriuretic peptide (NT-proBNP) after 60 minutes of swimming in male and female adults and adolescents with different pubertal status. STUDY DESIGN: Adolescent swimmers (25 male and 25 female) and adult swimmers (7 male and 9 female) participated in a 60-minute maximal swimming test with serial assessment of hs-cTnT and NT-proBNP at rest, immediately postexercise, and at 1, 3, 6, 12, and 24 hours postexercise. Adolescents were classified according to pubertal status: Tanner stages 3 (n = 14), 4 (n = 22), and 5 (n = 14). RESULTS: Exercise resulted in an increase in both biomarkers. hs-cTnT responses to exercise were similar in adolescents with different pubertal status and adults, although there was substantial individual variability in peak hs-cTnT, with the upper reference limit exceeding in 62% of the participants. Postexercise kinetics for hs-cTnT were largely consistent across all groups with a return to near baseline levels 24 hours postexercise. The male participants showed higher values of hs-cTnT at baseline and postexercise. All groups had similar NT-proBNP responses to acute exercise and recovery. One swimmer exceeded the upper reference limit for NT-proBNP. CONCLUSIONS: An exercise-associated increase in hs-cTnT and NT-proBNP occurred in response to a 60-minute maximal swimming test that was independent of pubertal status/adolescent vs adults. The present data also suggests that baseline and postexercise hs-cTnT values are higher in male compared with female, with no sex differences in NT-proBNP values.
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Peptídeo Natriurético Encefálico/sangue , Fragmentos de Peptídeos/sangue , Resistência Física/fisiologia , Natação/fisiologia , Troponina T/sangue , Adolescente , Adulto , Fatores Etários , Biomarcadores/sangue , Criança , Estudos Transversais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Fatores SexuaisRESUMO
The aim of this study was to examine the influence of hormonal status, anthropometric profile, sexual maturity level, and physical performance on the technical abilities of 40 young male soccer players during small-sided games (SSGs). Anthropometric profiling, saliva sampling, sexual maturity assessment (Tanner scale), and physical performance tests (Yo-Yo and vertical jumps) were conducted two weeks prior to the SSGs. Salivary testosterone was determined by the enzyme-linked immunosorbent assay method. Technical performance was determined by the frequency of actions during SSGs. Principal component analyses identified four technical actions of importance: total number of passes, effectiveness, goal attempts, and total tackles. A multivariate canonical correlation analysis was then employed to verify the prediction of a multiple dependent variables set (composed of four technical actions) from an independent set of variables, composed of testosterone concentration, stage of pubic hair and genitalia development, vertical jumps and Yo-Yo performance. A moderate-to-large relationship between the technical performance set and the independent set was observed. The canonical correlation was 0.75 with a canonical R2 of 0.45. The highest structure coefficient in the technical performance set was observed for tackles (0.77), while testosterone presented the highest structure coefficient (0.75) for the variables of the independent set. The current data suggest that the selected independent set of variables might be useful in predicting SSG performance in young soccer players. Coaches should be aware that physical development plays a key role in technical performance to avoid decision-making mistakes during the selection of young players.
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PURPOSE: To evaluate the graft diameter size after one-year follow-up or more of patients Tanner II, III, and IV who were submitted to anterior cruciate ligament reconstruction. METHODS: Ten patients [five males (mean age: 14.4 years) and five females (mean age: 13.6 years)] with open physis and anterior cruciate ligament tear were submitted to transphyseal anterior cruciate ligament reconstruction with quadruple hamstrings graft. During the procedure, graft and tunnel size were recorded. After last clinical follow-up (range 1-11 years), an MRI study was requested and their measurements near the tibial tunnel were compared with the graft diameter measured and used during primary procedure. RESULTS: Four patients had Tanner stage II, four patients Tanner stage III, and two Tanner IV. There were statistically significant decreases in the quadruple hamstrings graft diameter size (average of 25.3%). Mean size at time of surgery was 7.9 mm (±0.87), and mean size measured at different points of follow-up evaluation was 5.9 mm (±0.65). CONCLUSION: Diameter size of hamstring graft in skeletally immature patients is smaller in most cases. If there is a decrease in the diameter of the graft along postoperative time, the risk of a re-rupture is theoretically further increased. Quadruple hamstring graft decreases a mean 25.3% in diameter from time of anterior cruciate ligament reconstruction surgery until reassessment period in skeletally immature patients. LEVEL OF EVIDENCE: IV.
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Reconstrução do Ligamento Cruzado Anterior , Articulação do Joelho/crescimento & desenvolvimento , Imageamento por Ressonância Magnética , Tendões/anatomia & histologia , Tendões/transplante , Adolescente , Ligamento Cruzado Anterior/cirurgia , Feminino , Seguimentos , Humanos , Articulação do Joelho/cirurgia , MasculinoRESUMO
OBJECTIVE: To compare the associations between neuromuscular performance and anthropometric characteristics with habitual levels of physical activity in boys and girls during the initial stages of puberty. STUDY DESIGN: In a cross-sectional study of 72 healthy children (39 boys and 33 girls) ranging in age from 8 to 14 years, sex differences in anthropometric and motor performance characteristics were compared at 3 Tanner stages (T1-T3). Outcome variables included dual-energy x-ray absorptiometry measurements of body composition, assessments of neuromuscular function, and levels of physical activity (steps/day) measured by accelerometry. RESULTS: Physical activity was lower in girls than boys at T2 and T3, but there was no sex difference at T1. Physical activity increased with Tanner stage for boys but did not differ between Tanner stages in girls. Physical activity at each Tanner stage was strongly associated (R(2) > 0.85) with neuromuscular characteristics for both boys and girls, but percentage of body fat also was associated with physical activity for T3 girls. CONCLUSIONS: The attenuated gains in neuromuscular function experienced by girls in early stages of puberty were strongly associated with lower levels of physical activity, whereas the increase in physical activity exhibited by boys was mostly related to increases in the strength and endurance of leg muscles. Because sedentary activity is a known contributor to the development of obesity and type 2 diabetes in youth, this study helps to identify possible contributors to decreases in physical activity in young girls and provides potential targets for early intervention.
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Músculo Esquelético/fisiologia , Fenômenos Fisiológicos do Sistema Nervoso , Aptidão Física/fisiologia , Puberdade/fisiologia , Criança , Estudos Transversais , Feminino , Humanos , Masculino , Fatores SexuaisRESUMO
Introduction: Puberal development assessment (PDA) is performed according Tanner's method (TM). Objective: In order establish the coincidence between PDA determined by physicians and the self-evaluation by school-aged children. Material and Methods: 2 980 school children from Santiago, Chile, were assessed by means of TM, the development of the mammary gland (MD), male genitalia (MG) and pubic hair (PH) were assessed. PDA was simultaneously performed by physicians and by the school children. Results: Concordance between physicians and self assessment showed a kappa coefficient (KC) of 0.55, 0.45, and 0.51 in PH, MD and MG respectively, (acceptable KC > 0.61). Self-evaluation of PDA decreased as the age of children increased, with OR of 0.76 (95 percent IC 0.74 -0.79); 0.87 (95 percent IC 0.83 - 0.91) and 0.92 (95 percent IC 0.88 - 0.96) for PH, MD and MG respectively. An inverse relationship between nutritional status (NS) and PDA was observed only in PH, obese school children underscored their PH (OR 0.6; 95 percent IC 0.5 - 0.7). Multivariate analysis for gender and NS showed that only females overestimate their PH, OR of 1.15 (95 percent IC 1-1.32). Conclusions: PDA through self-assessment yields only moderate correlation coefficients, thus it is not reliable for making relevant clinical decisions.
Introducción: La determinación del desarrollo puberal (DDP) se evalúa según el método de Tanner (MT). Objetivo: Determinar la concordancia de la DDP entre médicos con la autoevaluación en escolares. Pacientes y Métodos: Se examinaron 2 980 escolares de Santiago de Chile. Se evalúo desarrollo mamario (DM), genitales masculinos (GM) y vello púbico (VP) mediante el MT. La DDP fue evaluada simultáneamente por un médico y por los escolares. Resultados: La concordancia entre médicos y la autoevaluación mostró un coeficiente kappa (CK) de 0,55, 0,45, 0,51 en VP, DM y GM respectivamente, (CK aceptable > 0,61). La autoevaluación del DDP disminuyo a medida que aumentaba la edad, con OR respectivos de 0,76 (95 por ciento IC 0,74-0,79); 0,87 (95 por ciento IC 0,83-0,91) y 0,92 (95 por ciento IC 0,88 -0,96) para VP, DM y GM. Se observo una relación inversa entre estado nutricional (EN) y DDP sólo en VP, escolares obesos subestimaban su VP (OR 0,6; 95 por ciento IC 0,5-0,7). El análisis multivariado de género y EN mostró que sólo las mujeres sobreestimaban su VP, OR de 1,15 (95 por ciento IC 1-1,32). Conclusiones: La DDP mediante autoevaluación obtiene coeficientes de correlación sólo moderados que no permiten confiar en este para establecer decisiones clínicas relevantes.
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Humanos , Masculino , Adolescente , Feminino , Criança , Autoexame/métodos , Puberdade/fisiologia , Antropometria , Imagem Corporal , Chile , Estudos Transversais , Cabelo/crescimento & desenvolvimento , Genitália/crescimento & desenvolvimento , Mama/crescimento & desenvolvimento , Estado Nutricional , Exame Físico , Reprodutibilidade dos Testes , Autoavaliação (Psicologia) , Caracteres SexuaisRESUMO
OBJECTIVE: Evaluate hormonal responses to incremental-stage exercise (EX) test to exhaustion in adolescents. SUBJECTS AND METHODS: Adolescents were tested at 16 years of age in Tanner Stage 4 (TS4) and at 17 years of age in Tanner Stage 5 (TS5) (n = 6). Adults were tested at 21 ± 1 y. (X ± SD) (n = 4) and served as controls. Blood samples were taken at rest, at the end of each EX stage. RESULTS: Main effects for EX in cortisol (p < 0.01, increasing with each EX stage) and for subject group for testosterone (T) occurred (p < 0.01; TS4 < TS5, adults). Interaction effect of group by EX stage occurred for GH (p < 0.05). GH increased in response to EX in all groups, however, the magnitude of increase was significantly less for TS5 and adults than TS4. CONCLUSIONS: Differences in T and GH responses for TS4 than those for TS5 and adults reflect the differing maturation levels of the endocrine system between Tanner Stages. TS5 adolescents are more similar to young adults in hormonal responses to EX than are TS4 adolescents.
OBJETIVO: Avaliar as respostas hormonais ao teste de exercício em estágios incrementais (EX) até exaustão. SUJEITOS E MÉTODOS: Foram examinados adolescentes com 16 anos de idade e índice Tanner 4 (TS4) e com 17 anos de idade e índice Tanner Stage 5 (TS5) (n = 6), e adultos com 21 ± 1 anos de idade. (X ± SD) (n = 4), estes últimos compondo o grupo controle. As amostras de sangue foram retiradas no repouso e ao final de cada estágio EX. RESULTADOS: Os principais efeitos observados no EX ocorreram no cortisol (p < 0,01, aumentou com a elevação do estágio EX) e no grupo de testosterona (p < 0,01; TS4 < TS5, adultos). Houve efeito de interação entre grupos e por estágio de EX no grupo de hormônio de crescimento (p < 0,05). O hormônio de crescimento aumentou em todos os grupos em resposta ao EX, no entanto, a magnitude dos aumentos observados foi significativamente menor em TS5 e nos adultos do que em TS4. CONCLUSÕES: As diferenças verificadas nas respostas dos grupos de testosterona e hormônio de crescimento em TS4 em relação ao TS5 e adultos refletem os diferentes níveis de maturação do sistema endócrino entre os estágios do índice de Tanner. Os adolescentes no TS5 se assimilam mais aos jovens adultos do que aos adolescentes TS4, quanto a suas respostas hormonais ao EX.
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Adolescente , Humanos , Masculino , Adulto Jovem , Exercício Físico/fisiologia , Hormônios/sangue , Esforço Físico/fisiologia , Análise de Variância , Desenvolvimento do Adolescente/fisiologia , Hormônios/classificação , Descanso/fisiologiaRESUMO
Um introdução ilustrada à teoria dimensional é utilizada para enfocar a questão do agrupamento de amostras que diferem alometricamente em tamanho. Nenhuma das idéias foram originadas pelo autor. Na realidade, os princípios são bem conhecidos. Os proponentes do índice de massa corporal que utilizam uma escala comum para indivíduos entre 20 e 65 anos de idade os ignoram escandalosamente. O erro ao agrupar amostras é demonstrado utilizando-se regressões log-log do peso em relação ao preditor altura para homens, mulheres e amostras combinadas de homens e mulheres em incrementos de 5 anos de 20 a 65 anos de idade. Este artigo serve como um convite para examinar a premissa da constância biológica ilustrada pelo tão conhecido índice de massa corporal, que nunca foi verdadeiro e, agora na era do microcomputador, é desnecesário.
An anecdotal introduction to dimensional theory is used to focus on the issue of combining samples that differ allometrically with size. None of the ideas are original with the author. Indeed, the principles are well-known. Proponents of the body mass index who propose a common scale for individuals 20 to 65 years old blatantly ignore them. The error of combining samples is demonstrated using log log regressions of weight on one predictor height for men, women, and combined samples of men and women in five-year age increments from age 20 to 65 years. This paper serves as an invitation to examine the assumption of biological constancy illustrated by the so-called body mass index that was never true and now in the microcomputer age is unnecessary.