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Megan E. Holmes, Jim Pivarnik, Karin Pfeiffer, Kimberly S. Maier, Joey C. Eisenmann and Martha Ewing

Background:

The role of psychosocial stress in the development of obesity and metabolic syndrome is receiving increased attention and has led to examination of whether physical activity may moderate the stress-metabolic syndrome relationship. The current study examined relationships among physical activity, stress, and metabolic syndrome in adolescents.

Methods:

Participants (N = 126; 57 girls, 69 boys) were assessed for anthropometry, psychosocial stress, physical activity, and metabolic syndrome variables; t tests were used to examine sex differences, and regression analysis was used to assess relationships among variables controlling for sex and maturity status.

Results:

Mean body mass index approached the 75th percentile for both sexes. Typical sex differences were observed for systolic blood pressure, time spent in moderate and vigorous physical activity, and perceived stress. Although stress was not associated with MetS (β = –.001, P = .82), a modest, positive relationship was observed with BMI (β = .20, P = .04).

Conclusions:

Strong relationships between physical activity and stress with MetS or BMI were not found in this sample. Results may be partially explained by overall good physical health status of the participants. Additional research in groups exhibiting varying degrees of health is needed.

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Andrew C. Fry, Carol C. Irwin, Justin X. Nicoll and David E. Ferebee

To determine absolute and relative (adjusted for body mass) strength, mean power, and mean velocity for upper and lower body resistance exercises, forty-seven young boys and girls participated in maximal strength testing. Healthy young boys and girls, ages 3- to 7-years old, were tested for one-repetition maximum (1-RM) strength, and 70% of 1-RM to determine mean power and mean velocity on the chest press and leg press exercises. Adult weight machines were modified to accommodate the smaller size and lower strength levels of the children. A 2 × 4 (sex × age) ANOVA was used to determine age and sex differences in performance. No interaction or sex differences were observed for any variable at any age. 1-RM strength, mean power, and mean velocity significantly increased across ages (p ≤ .05). When adjusted for body mass, the changes were insignificant, with one exception. Relative mean power for the bench press increased with age. Data indicated children from 3-7 years of age are capable of performing strength and power tests, but may require more attempts at maximal loads compared with adults. It appears that muscular strength and velocity during this stage of development are primarily dependent on increasing body mass, whereas power is influenced by additional variable(s).

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Blair Crewther, Zbigniew Obminski and Christian Cook

Purpose:

To examine the steroid hormone effect on the physical performance of young athletes during an Olympic weightlifting competition.

Methods:

26 boys and 26 girls were monitored across 2 weightlifting competitions. Pre- and post-competition testosterone (T), cortisol (C) and dehydroepiandrosterone-sulfate (DHEA-s) were measured in blood, with pre-event free T (FT) and the free androgen index (FAI) calculated. Body mass (BM) and weightlifting performance were recorded.

Results:

The boys had a larger BM, superior performance with more T, FT and a higher FAI than girls (p < .01). Although C (32%) and DHEA-s (8%) levels were elevated across competition, no sex differences in hormone reactivity were seen. In boys, DHEA-s correlated with performance (r = .46), but not after controlling for BM (r = .14). For girls, T correlated with performance (r = -0.51) after BM was controlled.

Conclusion:

The sex differences that emerge during puberty were observable, whereby the boys were larger and stronger with a more anabolic profile than girls. Individual DHEA-s (boys) and T (girls) levels were related to performance, but BM appeared to be acting as a mediating (boys) or suppressing (girls) variable. This adds new insight regarding the hormonal contribution to competitive performance in young athletes.

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Mary A. McElroy

Sport and nonsport career choices among economically disadvantaged adolescents enrolled in a summer sports program were explored. It was hypothesized that youngsters with sport career aspirations would demonstrate differences in sport-related attitudes and experiences when compared to youngsters with nonsport career aspirations. Nonsport career aspirations were categorized into two groups: one representing “high prestige” occupations and one representing “low prestige” occupations. Discriminant analysis revealed that disadvantaged youths' career aspirations were differentially related to the sport-related factors. Contrary to warnings of the potential dysfunctional consequences for those who aspire to sport careers, adolescents with sport career aspirations consistently scored higher on achievement-related socialization factors than those aspiring for traditional low-prestige occupations. Sex differences were noted and discussed in light of the role of sport in the lower class social environment.

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Thomas Rowland

Recognizing the cardiac features of athletically trained children bears importance for health care providers and exercise physiologists alike. This literature review reveals that ventricular enlargement and/or hypertrophy are commonly observed in studies of pre- and early-adolescent endurance athletes, yet the magnitude of these features is less than that described in adult athletes. Moreover, the upper range of values in child athletes is sufficiently small that clinical confusion with findings mimicking those in individuals with heart disease should not be expected to occur. In contrast to sex differences in the “athlete’s heart” in adults, cardiac structural findings in child athletes are similar in males and females. The extent that cardiac features observed in trained child athletes reflect a response to training or are influenced by genetic preselection remains uncertain.

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Sandra J. Shultz

Despite extensive research, we still do not fully understand the biological mechanisms that underlie a female's increased susceptibility for suffering a noncontact ACL injury. While sex differences in neuromuscular control are often implicated, prevention efforts addressing these differences have not resulted in a profound or sustainable reduction in injury rates. This paper will explore two likely scenarios that explain this greater susceptibility in females: (1) females have a structurally weaker ligament that is more prone or susceptible to failure at a given load (scenario #1), or (2) females develop less knee protection and experiences higher relative loads on the ACL (scenario #2). While we have learned much over the last two decades about ACL injury risk in females, much remains unknown. Continued research is of paramount importance if we are to effectively identify those females who are at greatest risk for injury and effectively reduce their susceptibility through appropriate interventions.

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Charles B. Corbin and Charles Nix

Elementary school children, 20 boys and 20 girls, served as subjects in this investigation designed to determine how children sex-typed each of three different motor activities and to study their success predictions before and after cross-sex competition. Results of the study indicated that both boys and girls sex-typed a motor task requiring strength, speed, and power as a “male” activity, while the two other motor tasks were characterized as “male-female.” The self-confidence levels of girls, as measured by success predictions were lower than boys prior to competition but only for the “male” activity. After cross-sex competition in which girls succeeded as often as the boys, self-confidence of girls was no different than for boys. There were no sex differences in postcompetition state anxiety levels. All subjects regardless of sex were more threatened after competing in a “male” as opposed to a “male-female” activity, and they experienced lower state anxiety following successful rather than unsuccessful competition.

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Lorayne Woodfield, Michael Duncan, Yahya Al-Nakeeb, Alan Nevill and Charles Jenkins

The present study examines the relationship of sex, ethnicity, and socio-economic status to physical activity levels of young people. Participants were 301 males and females (12.9 – 0.81 years). Physical activity was measured using the four by one-day physical activity recall questionnaire. ANOVA revealed that high socio-economic status children reported greater average daily energy expenditure levels than low socio-economic status children (p < .01). The daily energy expenditure of white-Caucasian children was significantly higher than black or Asian children. White boys were significantly more active than white girls, but no such sex differences were observed among black and Asian children. Although activity was always greater at weekends, a decline in activity by school year was observed on Saturdays and Sundays but with no such decline observed on weekdays.

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Amândio M.C. Santos, Joanne R. Welsman, Mark B.A. De Ste Croix and Neil Armstrong

Age- and sex-related differences in optimal peak power (PPopt) and associated measures determined using a force-velocity (F-V) cycling test were examined in pre teenage, teenage and adult males and females. Absolute PPopt increased significantly with age in both males and females. With body mass controlled for using allometric scaling significant age related increases remained, an effect masked in the females when PPopt was expressed as W • kg−1. Sex differences in PPopt were minimal in the preteens but males demonstrated higher PPopt than females in both teenage and adult groups. These patterns of change with age and sex broadly reflect those obtained for Wingate Anaerobic Test determined PP but the use of a single non-optimized braking force underestimates the magnitude of any differences observed.

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Daniel A. Galvão, Robert U. Newton and Dennis R. Taaffe

Resistance training has been shown to be the most effective exercise mode to induce anabolic adaptations in older men and women. Advances in imaging techniques and histochemistry have increased the ability to detect such changes, confirming the high level of adaptability that remains in aging skeletal muscle. This brief review presents a summary of the resistance-training studies that directly compare chronic anabolic responses to training in older (>60 years) men and women. Sixteen studies are summarized, most of which indicate similar relative anabolic responses between older men and women after resistance training. Relatively small sample sizes in most of the interventions limited their ability to detect significant sex differences and should be considered when interpreting these studies. Future research should incorporate larger sample sizes with multiple measurement time points for anabolic responses.