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Aristides M. Machado Rodrigues, Manuel J. Coelho e Silva, Jorge Mota, Sean P. Cumming, Lauren B. Sherar, Helen Neville and Robert M. Malina

Sex differences in physical activity (PA) through pubertal maturation and the growth spurt are often attributed to changing interests. The contribution of sex differences in biological maturation to the adolescent decline has received limited attention. This study examined the contribution of somatic maturation to sex differences in objective assessments of sedentary behavior and PA in Portuguese adolescents (N = 302, aged 13–16 years). Maturation was estimated from the percentage of predicted mature stature and physically active and inactive behaviors assessed with Actigraph GT1M accelerometers. The influence of age, sex and their interaction on body size, maturation and physical behaviors were examined using factorial ANOVA and, subsequently, ANCOVA (controlling for maturation) tested the effect of sex. Males spent more time in MVPA and less time in sedentary behavior than females. However, sex differences were attenuated when maturation was controlled; thus suggesting that maturity may play an important role in adolescent behaviors.

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Erin White, Jennifer D. Slane, Kelly L. Klump, S. Alexandra Burt and Jim Pivarnik

Background:

Knowing the extent to which genetic and environmental factors influence percent body fatness (%Fat) and physical activity (PA) would be beneficial, since both are tightly correlated with future health outcomes. Thus, the purpose was to evaluate sex differences in genetic and environmental influences on %Fat and physical activity behavior in male and female adolescent twins.

Methods:

Subjects were adolescent (age range 8.3 to 16.6 yr) twins. %Fat (n = 518 twins) was assessed by bioelectrical impedance analysis (BIA) and PA (n = 296 twins) was measured using 3-Day PA Recall. Each activity was converted to total MET-minutes. Univariate twin models were used to examine sex differences in genetic and environmental factors influencing %Fat and PA.

Results:

%Fat was influenced by genetic effects in both boys and girls (88% and 90%, respectively), with slightly higher heritability estimates for girls. PA was influenced solely by environmental effects for both sexes with higher shared environmental influences in boys (66%) and higher nonshared effects in girls (67%).

Conclusions:

When developing interventions to increase PA in adolescents, it is important to consider the environment in which it takes place as it is the primary contributor to PA levels.

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Cale Jacobs and Carl Mattacola

Context:

Decelerating movements such as landing from a jump have been proposed to be a common mechanism of injury to the anterior cruciate ligament (ACL).

Objective:

To compare eccentric hip-abductor strength and kinematics of landing between men and women when performing a hopping task.

Setting:

Research laboratory.

Patients:

18 healthy subjects (10 women, 8 men).

Main Outcome Measures:

Eccentric peak torque of the hip abductors and peak knee-joint angles during a 350-millisecond interval after impact.

Results:

No significant sex differences were present, but there was a significant inverse relationship between women's eccentric peak torque and peak knee-valgus angle (r = –.61, P = .03).

Conclusions:

Women with larger eccentric peak torque demonstrated lower peak knee-valgus angles. By not reaching as large of a valgus angle, there is potentially less stress on the ACL. Increasing eccentric hip-abductor strength might improve knee-joint kinematics during landing from a jump.

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Dane R. Van Domelen, Paolo Caserotti, Robert J. Brychta, Tamara B. Harris, Kushang V. Patel, Kong Y. Chen, Nanna Ýr Arnardóttir, Gudny Eirikdottir, Lenore J. Launer, Vilmundur Gudnason, Thórarinn Sveinsson, Erlingur Jóhannsson and Annemarie Koster

Background:

Accelerometers have emerged as a useful tool for measuring free-living physical activity in epidemiological studies. Validity of activity estimates depends on the assumption that measurements are equivalent for males and females while performing activities of the same intensity. The primary purpose of this study was to compare accelerometer count values in males and females undergoing a standardized 6-minute walk test.

Methods:

The study population was older adults (78.6 ± 4.1 years) from the AGES-Reykjavik Study (N = 319). Participants performed a 6-minute walk test at a self-selected fast pace while wearing an ActiGraph GT3X at the hip. Vertical axis counts·s−1 was the primary outcome. Covariates included walking speed, height, weight, BMI, waist circumference, femur length, and step length.

Results:

On average, males walked 7.2% faster than females (1.31 vs. 1.22 m·s−1, P < .001) and had 32.3% greater vertical axis counts·s−1 (54.6 vs. 39.4 counts·s−1, P < .001). Accounting for walking speed reduced the sex difference to 19.2% and accounting for step length further reduced the difference to 13.4% (P < .001).

Conclusion:

Vertical axis counts·s−1 were disproportionally greater in males even after adjustment for walking speed. This difference could confound free-living activity estimates.

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Timothy C. Mauntel, Eric G. Post, Darin A. Padua and David R. Bell

A disparity exists between the rates of male and female lower extremity injuries. One factor that may contribute to this disparity is high-risk biomechanical patterns that are commonly displayed by females. It is unknown what biomechanical differences exist between males and females during an overhead squat. This study compared lower extremity biomechanics during an overhead squat and ranges of motion between males and females. An electromagnetic motion tracking system interfaced with a force platform was used to quantify peak lower extremity kinematics and kinetics during the descent phase of each squat. Range of motion measurements were assessed with a standard goniometer. Differences between male and female kinematics, kinetics, and ranges of motion were identified with t tests. Males displayed greater peak knee valgus angle, peak hip flexion angle, peak vertical ground reaction forces, and peak hip extension moments. Males also displayed less active ankle dorsiflexion with the knee extended and hip internal and external rotation than females. No other differences were observed. The biomechanical differences between males and females during the overhead squat may result from differences in lower extremity ranges of motion. Therefore, sex-specific injury prevention programs should be developed to improve biomechanics and ranges of motion.

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John H. Lewko and Martha E. Ewing

Children (N = 370), ages 9 to 11 years, responded to a fixed-alternative questionnaire which examined the influences of mothers, fathers, sisters, and brothers on the sport involvement of males and females. The following predictions were tested: (a) at similar levels of involvement (high or low), males would be discriminated from females by significant others; (b) value toward sport would discriminate between high- and low-involved males and females; (c) for high levels of involvement, fathers would be the most discriminating variable for both males and females. Within-sex discriminant analyses revealed fathers as predominant socializing agents for high-involved males, while all agents discriminated between high/low females. Between-sex discriminant analyses revealed significant differences only for high-involved males and females. Results were discussed in terms of early parental socialization practices and the support/encouragement necessary to increase sport involvement, particularly for females.

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Jennifer M. Medina McKeon, Craig R. Denegar and Jay Hertel

The purpose of this study was to formulate a predictive equation to discriminate males from females using static and dynamic lower extremity (LE) alignments. Twenty-four healthy adults volunteered to participate. Three-dimensional motion analysis was used to assess the kinematics of the right hip and knee during two functional tasks. Six measures of static LE alignment were also performed. Statistical comparisons were made between males and females for all variables. Static and dynamic variables that were significantly different by sex were entered into separate discriminant analyses for each task. The resulting equations were each able to correctly predict 87% of the subjects by sex. Fifty-eight percent and 55% of the variance was explained by sex for the vertical jump and plant & jump, respectively. The frontal plane hip angle was the best predictor of sex for both tasks. While there were statistically significant differences between the sexes for static measures of LE alignment, kinematic measures were better at discriminating between sexes.

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Simone A. Kaptein and Elizabeth M. Badley

Objective:

To examine physical activity (PA) prevalence in individuals with arthritis in comparison with those with other chronic diseases.

Methods:

Descriptive analyses were based on cross-sectional self-reported data for adults over age 18 from the Canadian Community Health Survey administered in 2005 (N = 132,221) for the following groups: arthritis, back problems, other physical chronic conditions (ie, diabetes, heart disease, hypertension, and cancer), and no physical chronic conditions.

Results:

The arthritis group did less leisure-time physical activity than the other 3 groups, they were particularly less likely to engage in vigorous physical activities, but were just as likely to walk when commuting for errands, work, or school. Older women in the arthritis group appeared to be the least active across physical activities and groups.

Conclusions:

Adults with chronic disease were more physically inactive during leisure than those without chronic physical conditions, and older women in the arthritis group were particularly limited in our study. A more comprehensive assessment of all types of physical activity, including work, leisure, and commuting behaviors, need to be done in populations with chronic disease, to provide a more accurate portrayal of physical activity participation.

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John T. Cacioppo and Charlotte A. Lowell

Eight situations dealing with team sports were described to 63 male and 63 female undergraduates. Each situation depicted a team competition involving same-sex members, and subjects were told specifically about the affiliation, acquaintance, and skill of one of the participants. Subjects indicated how enjoyable they viewed each of the eight sports situations, how many years they had participated in team sports, and how much experience they had in team sport competition. The results suggested that men and women similarly enjoyed aspects of team sport participation that improved their chances of winning and interacting cooperatively with friends, but men seemed to enjoy the ego-challenging aspects of team sports more than women.

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Pantelis T. Nikolaidis, Stefania Di Gangi and Beat Knechtle

performance between women and men. To elucidate these assumptions, we investigated the relationship between half-marathon race times and age in 1-year intervals, using the world single age records in half-marathon running and the sex difference in performance from 5 to 91 years in men and 5 to 93 years in