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Nancy L. Greer, Joseph Hamill and Kevin R. Campbell

Ground reaction force patterns during walking were observed in 18 children 3 and 4 years of age. The children walked barefoot at a self-chosen walking pace. Selected variables representing the vertical, anteroposterior, and mediolateral force components were evaluated. The results indicated that children in this age range contact the ground with greater vertical force measures relative to body mass than do adults. In addition, the minimum vertical force was lower, the transition from braking to propulsion occurred earlier, and the mediolateral force excursions were higher than typically found in adults. When the children were divided into groups on the basis of sex, differences were observed between those groups. The boys exhibited a greater difference in the vertical peak forces, a lower minimum force, a greater braking force, and a higher mediolateral force excursion value. The results indicated that children display a different ground reaction force pattern than do adults and that differences between boys and girls may be observed as early as ages 3 and 4 years.

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Maïtel Botcazou, Christophe Jacob, Arlette Gratas-Delamarche, Sophie Vincent, Danièle Bentué-Ferrer, Paul Delamarche and Hassane Zouhal

The purpose of this study was to clarify the effect of sex on plasma catecholamine responses to sprint exercise in adolescents and adults. Thirty-six untrained participants took part in this study—9 girls and 10 boys (Tanner Stage 4) and 9 women and 8 men. Each participant performed a 6-s sprint test on a cycle ergometer. Plasma adrenaline (A) and noradrenaline (NA) concentrations were determined successively at rest (A0 and NA0), immediately after the 6-s sprint test (AEX and NAEX), and after 5 min of recovery (A5 and NA5). Peak power, expressed in absolute values or relative to body weight and fat-free mass, was significantly higher in boys than in girls and higher in men than in women (p < .001). No sex effect was observed in AEX in the adolescents, but the NA increase was significantly higher in boys in response to the 6-s sprint (p < .05). In adults, no sex difference was found in NAEX, but AEX was significantly higher in men than in women (p < .05). NAEX was significantly higher in women than in girls (p < .05), and AEX was significantly higher in men than in boys (p < .01). The results of this study suggest that male and female adolescents and young adults might exhibit different catecholamine responses to sprint exercise.

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Élvio R. Gouveia, José A. Maia, Gaston P. Beunen, Cameron J. Blimkie, Ercília M. Fena and Duarte L. Freitas

The purposes of this study were to generate functional-fitness norms for Portuguese older adults, to determine age and sex differences, and to analyze the physical activity–associated variation in functional fitness. The sample was composed of 802 older adults, 401 men and 401 women, age 60–79 yr. Functional fitness was assessed using the Senior Fitness Test. Physical activity level was estimated via the Baecke questionnaire. The P50 values decreased from 60 to 64 to 75 to 79 yr of age. A significant main effect for age group was found in all functional-fitness tests. Men scored significantly better than women in the chair stand, 8-ft up-and-go, and 6-min walk. Women scored significantly better than men in chair sit-and-reach and back scratch. Active participants scored better in functional-fitness tests than their average and nonactive peers. This study showed a decline in functional fitness with age, better performance of men, and increased proficiency in active participants.

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Katie E. Gunnell, Jennifer Brunet, Erin K. Wing and Mathieu Bélanger

Background:

Perceived barriers to moderate-to-vigorous physical activity (PA) may contribute to the low rates of moderate-to-vigorous PA in adolescents. We examined the psychometric properties of scores from the perceived barriers to moderate-to-vigorous PA scale (PB-MVPA) by examining composite reliability and validity evidence based on the internal structure of the PB-MVPA and relations with other variables.

Methods:

This study was a cross-sectional analysis of data collected in 2013 from adolescents (N = 507; Mage = 12.40, SD = .62) via self-report scales.

Results:

Using exploratory and confirmatory factor analyses, we found that perceived barriers were best represented as two factors representing internal (e.g., “I am not interested in physical activity”) and external (e.g., “I need equipment I don’t have”) dimensions. Composite reliability was over .80. Using multiple regression to examine the relationship between perceived barriers and moderate-to-vigorous PA, we found that perceived internal barriers were inversely related to moderate-to-vigorous PA (β = -.32, p < .05). Based on results of the analysis of variances, there were no known-group sex differences for perceived internal and external barriers (p < .26).

Conclusions:

The PB-MVPA scale demonstrated evidence of score reliability and validity. To improve the understanding of the impact of perceived barriers on moderate-to-vigorous PA in adolescents, researchers should examine internal and external barriers separately.

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Alejandro Santos-Lozano, Ana M. Angulo, Pilar S. Collado, Fabian Sanchis-Gomar, Helios Pareja-Galeano, Carmen Fiuza-Luces, Alejandro Lucia and Nuria Garatachea

Most studies on aging and marathon have analyzed elite marathoners, yet the latter only represent a very small fraction of all marathon participants. In addition, analysis of variance or unpaired Student t tests are frequently used to compare mean performance times across age groups. In this report the authors propose an alternative methodology to determine the impact of aging on marathon performance in both nonelite and elite marathoners participating in the New York City Marathon. In all, 471,453 data points corresponding to 370,741 different runners over 13 race editions (1999–2011) were retrieved. Results showed that the effect of aging on marathon performance was overall comparable in both sexes, the effect of aging differed between the fastest and slowest runners in both sexes, and the magnitude of the sex differences was higher in the slowest runners than in the fastest ones. Current data suggest that the biological differences between sexes allow men to have better marathon performance across most of the human life span.

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Chung Gun Lee, Youngtae Cho and Seunghyun Yoo

Purpose:

Suicide is the leading cause of death among Korean adolescents. This study investigates the cross-sectional relations of physical activity with suicidal ideation and attempts in adolescents, simultaneously considering previously reported risk factors of suicide such as depression, stress, and body image.

Methods:

This study used the 2007 Korea Youth Risk Behavior Web-based Survey (KYRBWS). Four hundred middle schools and 400 high schools in Korea were monitored, and 74,698 students completed the questionnaire. Logistic regression analysis was conducted to investigate the relationship between physical activity and suicidal ideation and attempts, progressively adjusting for body image, depression and stress.

Results:

After controlling for body image, stress, and depression, the significant relationship between physical activity and suicidal ideation disappeared, and the only remaining relationship was a positive relationship between frequent vigorous physical activity and suicide attempts. No sex differences were found after adjusting for all the variables.

Conclusion:

Unlike the general expectation that physical activity protects adolescents from suicidal behaviors, the results from this study suggest that physical activity does not have protective effect. Korean adolescents who perform frequent vigorous physical activities are more likely to attempt suicide.

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Joaquin A. Barrios and Danielle E. Strotman

The prevalence of medial knee osteoarthritis is greater in females and is associated with varus knee alignment. During gait, medial knee osteoarthritis has been linked to numerous alterations. Interestingly, there has been no research exploring sex differences during walking in healthy individuals with and without varus alignment. Therefore, the gait mechanics of 30 asymptomatic individuals with varus knees (15 females) and 30 normally-aligned controls (15 females) were recorded. Gait parameters associated with medial knee osteoarthritis were analyzed with two-factor analyses of variance. In result, varus males exhibited the greatest peak knee adduction moments, while normal females showed the greatest peak hip adduction angles and pelvic drop excursions. By sex, females exhibited greater peak hip adduction angles and moments and greater pelvic drop excursion, but lesser peak knee adduction angles. By alignment type, varus subjects exhibited greater peak knee adduction angles and moments, midstance knee flexion angles and excursion, and eversion angles and lateral ground reaction forces, but lesser peak hip adduction angles. In conclusion, females generally presented with proximal mechanics related to greater hip adduction, whereas males presented with more knee adduction. Varus subjects demonstrated a number of alterations associated with medial knee osteoarthritis. The differential sex effects were far less conclusive.

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Brandi M. Eveland-Sayers, Richard S. Farley, Dana K. Fuller, Don W. Morgan and Jennifer L. Caputo

Background:

The benefits of physical fitness are widely acknowledged and extend across many domains of wellness. The association between fitness and academic achievement, however, remains to be clarified, especially in young children. Therefore, the purpose of this study was to examine the relationship between fitness and academic achievement in elementary school children.

Methods:

Data were collected from 134 third-, fourth-, and fifth-grade children. One-mile run time, body mass index, curl-up, and sit-and-reach data were collected from physical education instructors in Middle Tennessee. The percentage of questions answered correctly for the mathematics and reading/language arts sections of the Terra-Nova achievement test was taken as a measure of academic achievement.

Results:

A negative association (P < .01) was noted between 1-mile run times and mathematics scores (r = –.28), whereas a positive relationship (P < .05) was observed between muscular fitness and mathematics scores (r = .20). Relative to sex differences, inverse relationships (P < .05) were observed between 1-mile run times and reading/language arts and mathematics scores in girls (r = –.31 and –.36, respectively), but no significant associations were evident in boys.

Conclusions:

Results from this study support a link between specific components of physical fitness and academic achievement in elementary school children.

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Magnus Carlsson, Tomas Carlsson, Daniel Hammarström, Christer Malm and Michail Tonkonogi

Purpose:

To investigate the relationship between race performance and lean mass (LM) variables, as well as to examine sex differences in body composition in elite-standard cross-country skiers.

Methods:

Thirty-four elite cross-country skiers (18 men and 16 women) underwent a dual-emission X-ray-absorptiometry body-composition test to determine LM, fat mass, and bone mineral content. For both sexes, performance data were collected from a sprint prologue and a distance race.

Results:

The absolute expression of LM variables (whole-body [LMWB], upper body [LMUB], and lower body [LMLB]) was significantly correlated with finishing time in the sprint prologue independent of sex. Distance-race performance was significantly related to LMWB, LMUB, and LMLB in women; however, no correlation was found in men. Men had a significantly higher LM and lower fat mass, independent of expression (absolute or relative), for the whole body, arms, trunk, and legs, except for the absolute fat mass in the trunk.

Conclusions:

The absolute expressions of LMWB, LMUB, and LMLB were significant predictors of sprint-prologue performance in both sexes, as well as of distance-race performance in women only. Compared with women, male skiers have a higher LM in the body segments that are major contributors to propelling forces. These results suggest that muscle mass in the lower and upper body is equally important for race performance; thus, more focus of elite skiers’ training should be directed to increasing whole-body muscle mass to improve their competitive performance capability.

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Bart C. Bongers, Maarten S. Werkman, Donna Blokland, Maria J.C. Eijsermans, Patrick van der Torre, Bart Bartels, Olaf Verschuren and Tim Takken

Purpose:

To determine criterion validity of the pediatric running-based anaerobic sprint test (RAST) as a nonsophisticated field test for evaluating anaerobic performance in healthy children and adolescents.

Methods:

Data from 65 healthy children (28 boys and 37 girls between 6 and 18 years of age, mean ± SD age: 10.0 ± 2.8 years) who completed both the pediatric RAST and the 30-s Wingate anaerobic test (WAnT) on a cycle ergometer in a randomized order were analyzed. Peak power (PP) and mean power (MP) were the primary outcome measures for both tests.

Results:

There were no significant sex-differences in PP and MP attained at the pediatric RAST and the WAnT. Age was strongly correlated to pediatric RAST and WAnT performance (Spearman’s rho values ranging from 0.85 to 0.90, with p < .001 for all coefficients). We found high correlation coefficients between pediatric RAST performance and WAnT performance for both PP (Spearman’s rho: 0.86; p < .001) and MP (Spearman’s rho: 0.91; p < .001).

Conclusion:

The pediatric RAST can be used as a valid and nonsophisticated field test for the assessment of anaerobic performance in healthy children and adolescents. For clinical evaluative purposes, we suggest to use MP of the pediatric RAST when assessing glycolytic power in the absence of the WAnT.