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Belinda R. Beck

Puberty ensues when marked alterations in circulating hormones in childhood stimulate dramatic physical and physiological transformations. It is, therefore, small wonder that the body can be observed to respond differently to certain stimuli according to the timing of the provocation in relation to

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Noreen D. Willows, Susan K. Grimston, David J. Smith and David A. Hanley

This study assessed change in hematological status among physically active children as they progressed through puberty. Values for serum ferritin, hemoglobin, and hematocrit at all stages of puberty were within the normal range of reference values. Significant changes in serum ferritin were not detected in the different pubertal stages, although serum ferritin was highest in prepubertal boys and girls. There were no significant differences in marginal or deficient iron stores between the sexes at any pubertal stage, suggesting that gender was not predisposing for iron deficiency; however, girls had a greater overall incidence for both measures. With more children under consideration, these trends may have reached significance. Boys in TS4 and TS5 had higher hemoglobin and hematocrit compared with earlier stages of puberty, and compared with girls at the same stages of puberty. This can be explained by testosterone production in boys. Among girls, pubertal progression had no significant effect on hemoglobin or hematocrit. In the absence of controls, there was no direct evidence that involvement in sports had an adverse effect on iron status.

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Robert G. McMurray and Peter A. Hosick

The study evaluated the interactions of puberty and obesity on substrate oxidation of overweight girls (n = 38) and boys (N = 35; BMI > 85th percentile) matched for gender, age, and puberty (pre/pubertal) with normal weight girls and boys. Metabolic rates (VO2) were obtained during rest and at 4, 5.6 and 8 k/h. Carbohydrate oxidation rates (mg/kgFFM/min) adjusted for % predicted VO2max, were higher for prepubertal OW children than pubertal children (p < .03). Fat oxidation rates were higher for NW prepubertal boys compared with other boys. Results indicate that OW children, regardless of gender or pubertal status, increase their carbohydrate oxidation rate to compensate for higher than normal metabolic rates. The effects of obesity on the substrate use is marginally related to puberty.

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Gretchen E. Iversen

Research on the psychosocial aspects of maturational timing has not addressed the experience of the late-developing gymnast. Studies to date have used conceptual and timing frameworks incommensurate with the experience of the athlete who reaches puberty in late adolescence. The role of environmental influences, including the support group, in a gymnast’s experience of puberty is salient. In order for sports practitioners to help late maturing female gymnasts deal with their personal and physical development, a reconceptualization of the related psychosocial parameters is needed.

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Noreen D. Willows, Susan K. Grimston, Delia Roberts, David J. Smith and David A. Hanley

This study assessed serum ferritin, hemoglobin, and hematocrit among 107 physically active young people 9 to 18 years of age. Tanner stage (TS) of puberty was assessed and subjects were categorized as prepubertal (TS 1), midpubertal (TS 2, 3, and 4, excluding menarcheal females) and going through their rapid growth phase, or late pubertal (TS 5 and menarcheal females) and having completed their rapid growth phase. Midpubertal females had a lower hematocrit than late pubertal females, but there were no significant differences in serum ferritin or hemoglobin between pubertal groups. Late pubertal males had hemoglobin and hematocrit values that were higher than among prepubertal males, but serum ferritin did not differ. At late puberty the males had significantly higher serum ferritin, hemoglobin, and hematocrit compared with late pubertal females, and females in late puberty were more likely to have marginal iron stores compared with males at the same stage of pubertal development. Midpubertal and late pubertal females reported a diet low in absorbed iron, which could contribute to their poorer iron status.

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Jorge Arede, António Paulo Ferreira, Oliver Gonzalo-Skok and Nuno Leite

ball throw test in 14-year-old players. 20 Mature players performed this test significantly better than the late puberty and midpuberty players. Body mass seems to be the determinant for upper-body strength and power. 20 Interestingly, the postpubertal group was significantly heavier than other

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Kathleen F. Janz, Jeffrey D. Dawson and Larry T. Mahoney

To evaluate the effect of changes in aerobic fitness and physical activity on changes in lipoproteins, we measured body composition, peak V̇O2, vigorous and sedentary activity, maturation, and lipoproteins in 125 children (mean baseline age, 10.5 years) for 5 years. Change in variables was analyzed using the slopes of the regression line obtained by plotting the data for each child. No predictor variables were significant for girls. In boys, predictors of favorable changes in lipoproteins included decreases in fatness, increases in fitness, early maturation, and increases in fat-free body mass (FFM). Multivariable analysis, adjusted for baseline age, indicated that change in FFM explained 21% of the variability in change in LDL-C. Results suggest that during puberty, changes in activity and fitness do not predict changes in lipoproteins.

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Kristel Võsoberg, Vallo Tillmann, Anna-Liisa Tamm, Toivo Jürimäe, Meeli Saar, Katre Maasalu, Inga Neissaar, Evelin Lätt and Jaak Jürimäe

The aim of this study was to describe longitudinal changes in body composition, leptin, adiponectin, and ghrelin over a 36-month period in prepubertal rhythmic gymnasts (RG) and their age-matched untrained controls (UC) entering into puberty. Thirty-five RG (8.0 ± 0.6 yrs) and 33 UC (8.2 ± 0.6 yrs) were followed at 12-month intervals for the next 3 years. Height, weight, pubertal stage, body composition, leptin, adiponectin, and ghrelin were measured at each time points. The pubertal development over the next 36 months was slower in the RG compared with UC. Leptin was increased in UC and remained unchanged in RG over 3-year study period (3.7 ± 3.6 vs. 0.2 ± 1.1 ng/ml; p < .05). In RG, baseline leptin was negatively correlated with the change in body fat percentage over a 36-month period (r = −0.34; p < .05). The change in adiponectin over the study period was negatively correlated with the change in BMI (r = −0.43; p < .05). RG had relative leptin deficiency per body fat mass. In conclusion, relatively high leptin concentration at the beginning of puberty may predict those girls who do not increase their body fat percentage through coming years and therefore may have increased risk for delayed puberty.

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Sidnei Jorge Fonseca-Junior, Aldair J. Oliveira, Luiz Lannes Loureiro and Anna Paola Trindade Pierucci

Purpose:

Body composition of adolescent athletes is often evaluated scientifically and in sports by using reference equations developed from nonathlete adolescent populations. The aim of this study was to analyze the validity of predictive equations based on skinfold measurements, as compared with dual-energy X-ray absorptiometry (DXA), to estimate body fat in adolescent modern pentathlon athletes.

Methods:

51 athletes, 27 male (mean age = 15.1 years; standard deviation, SD = 1.5 years) and 24 female (mean age = 14.2 years; SD = 2.5 years), were assessed using DXA, anthropometric parameters, sports practice anamnesis, and pubertal stages. Agreement between methods was tested with boxplots of mean comparisons using Student’s t test (p < .05), and Bland-Altman plots.

Results:

The body density equations of Durnin & Rahaman (1967) and Durnin & Womersley (1974) showed better agreement with DXA than the other predictive equations, for both females (difference between means=-2.03; 2SD = 8.44) and males (difference between means = 0.98; 2SD = 7.30). There were no mean differences between these equations and the reference method (DXA; p > .05), but they did display high variability (2SD).

Conclusion:

The high variability among results indicated imprecision. Predictive skinfold equations developed for nonathlete adolescents do not offer good validity for modern adolescent pentathlon athletes, and should be avoided.

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Tuomo Rankinen, Mikael Fogelholm, Urho Kujala, Rainer Rauramaa and Matti Uusitupa

Dietary intakes, trace element status, and anthropometric measures were studied in 12- to 13-year-old boys (n = 49) playing ice hockey (AB) and in 11- to 12-year-old girls who were gymnasts, figure skaters, and runners (AG; n = 43), Thirty-five boys (CB) and 53 girls (CG) not involved in supervised sports were controls. After adjustment for sexual maturation, ABs had larger upper arm muscle circumference than CBs. The sum of four skinfolds was smaller in AGs than in CGs. The intake of energy and all micronutrients examined was higher in ABs than in CBs. Micronu-trient Intakes were not different between AGs and CGs. Compared to CBs, serum ferritin and copper concentrations were lower, but serum zinc concentration was higher in ABs. No differences in trace element status were found between AGs and CGs. Blood investigations did not indicate inadequate trace element status in any of the groups studied.