Physical Activity In Boys Research Articles

Physical Activity in Boys With Duchenne Muscular Dystrophy Is Lower and Less Demanding Compared to Healthy Boys.

This study describes the amount of physical activity and perception of physical activity in boys with Duchenne muscular dystrophy (DMD) compared to healthy boys. A questionnaire described 6 domains of physical activity. Four Duchenne muscular dystrophy subgroups were made: early and late ambulatory, nonambulatory with relative good, or limited arm function. Eighty-four boys with Duchenne muscular dystrophy (15.0 ± 6.4 years) and 198 healthy boys (14.0 ± 4.3 years) participated. Daily activities were more passive for boys with Duchenne muscular dystrophy. Physical activity was less and low demanding compared to healthy boys. It decreased with disease severity ( P < .05), whereas screen time increased ( P < .05). Benefits of physical activity in boys with Duchenne muscular dystrophy were having fun and making friends. Barriers were lack of sport facilities and insufficient health. This study helps to quantify poor engagement in physical activity by boys with Duchenne muscular dystrophy, and demonstrates factors that contribute to it. Suggestions to stimulate physical activity are made.

Associations of sedentary behavior and physical activity with physical measurements and dyslipidemia in school-age children: a cross-sectional study.

BackgroundPhysical activity and sedentary behavior are common factors influencing cardiovascular health. However, how school and leisure-time activity/sedentary behavior are associated with physical fitness and blood lipid levels in primary school children in consideration of gender disparity remains unclear.MethodsData was obtained from a health and nutrition survey on primary school children from nine areas in China. The association between physical activities/sedentary behaviors (school and leisure-time physical activity levels, screen time, and other sedentary behaviors) and anthropometric measurements/prevalence of dyslipidemia were examined by multilevel analysis (the individual level, class level, grade level, and investigation area level) adjusted for age, energy intake and family income.ResultsA total of 770 participants (average age = 9.4 ± 1.7 years) were included. Prevalence of dyslipidemia was 10.9%. Prevalence of dyslipidemia was associated with screen time in boys [OR = 3.04, 95% CI (1.24–7.45)] and inversely associated with leisure-time physical activity in boys [OR = 2.22, 95% CI (1.08–4.56)] and school-time activity in girls [OR = 5.34, 95% CI (1.18–24.16)].ConclusionsPhysical activity—but not sedentary behavior—was significantly associated with dyslipidemia in both genders. Increasing leisure-time physical activity for boys and school-time physical activity for girls may be critical.

Physical Activity in Early Adolescence and Pulmonary Function Gain From 15 to 18 Years of Age in a Birth Cohort in Brazil.

The aim of this study was to evaluate the association between physical activity from 11 to 15 years of age and pulmonary function (PF) gain from 15 to 18 years of age among adolescents in a birth cohort in Brazil. Longitudinal analysis of the individuals participating in the 1993 Pelotas Birth Cohort Study. Physical activity was assessed by self-report at ages 11 and 15, spirometry was performed at ages 15 and 18 (n = 3571). Outcome variables assessed were gains in forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC) and peak expiratory flow (PEF). Crude and adjusted linear regressions, stratified by sex, and mediation analyses were performed. Boys who were active (leisure-time and total physical activity) at ages 11 and 15 had higher gains in FEV1, FVC, and PEF than those who were inactive. Vigorous-intensity physical activity in boys was also associated with FEV1 and FVC gains. Mediation analyses showed that height at age 18 accounted for 5% to 75% of the association between physical activity and PF gains. No significant associations were found among girls. Physical activity in early adolescence is associated with gains in PF by the end of adolescence in boys.

25(oh) Vitamin D Is Associated With Cardiorespiratory Fitness In Preschool- Aged Boys, But Not In Girls

Vitamin D deficiency has been associated with poor cardiorespiratory fitness in adolescents and adults, but this association is unclear in preschool aged children. PURPOSE: to determine the association between serum 25(OH)D concentration and cardiorespiratory fitness in preschool-aged children, and whether these are any gender differences in this association. METHODS:The participants were 137 preschool children (45% were girls) aged 4 and 5 years (mean height: 112.1±4.9 cm; weight: 20.5±3.4kg) participated in this study. Cardiorespiratory fitness (maximal oxygen uptake, VO2max) was measured with the 20-meter shuttle run test. Fasting blood samples were collected for the determination of plasma 25(OH)D and iPTH concentrations using commercially available ELISA kits. Multiple linear regressions were used to assess whether serum 25(OH)D concentration was associated with VO2max adjusted for potential confounding variables (BMI, season, and physical activity). RESULTS:The mean 25(OH)D concentration was 58.1±14.3 nmol/L, 29.9% of children were 25(OH)D deficient (<50 nmol/L), and 56.2% of children had insufficient 25(OH)D (50-75 nmol/L). Multiple linear regression analysis revealed that Serum 25(OH)D concentration was positively associated with VO2max independently of BMI, season, and objectively measured physical activity in boys (Beta = 0.22, P = 0.046), but not in girls (Beta = 0.02, P = 0.904). CONCLUSIONS:These findings suggest that serum 25(OH)D concentration is independently and positively related to cardiorespiratory fitness in preschool-aged boys, but not in girls. These findings indicate that the prevention and treatment of vitamin D deficiency may help to maintain and improve cardiorespiratory fitness in preschool-aged boys.

Physical Activity During Adolescence and Lung Function Gain from 15 to 18 Years of Age

A low prevalence of physical activity is found in all age groups worldwide. Although physical activity is associated with many health outcomes, the relationship with lung function remains poorly elucidated in the literature. PURPOSE: To evaluate the association between physical activity from 11 to 15 years of age with lung function gain from 15 to 18 years of age among adolescents belonging to a birth cohort in Brazil. METHODS: 5,249 live births in Pelotas (Brazil) participated in the 1993 Pelotas Birth Cohort Study. At ages 11, 15, and 18 years, all participants were sought for followed-up (follow-up rates: 87.5%, 85.7% and 81.3%, respectively). Physical activity (leisure-time and total) was self-reported at 11 and 15 years, while spirometric tests were performed at 15 and 18 years. Outcome variables were gains in forced expiratory volume in one second, forced vital capacity, and peak expiratory flow expressed as z-scores. Crude and adjusted linear regressions, stratified by sex, were performed. RESULTS: In adjusted analyses active boys at 11 and 15 years in leisure-time and total physical activity had higher gains in forced expiratory volume in one second (β=0.177; 95%CI:0.063;0.290, β=0.137; 95%CI:0.017;0.258), forced vital capacity (β=0.146; 95%CI:0.054;0.237, β=0.113; 95%CI:0.016;0.210), and peak expiratory flow (β=0.202; 95%CI:0066;0.338, β=0.149; 95%CI:0.005;0.293) than inactive ones. Vigorous-intensity physical activity in boys was also associated with gains in forced expiratory volume in one second (β=0.136; 95%CI:0.016;0.257) and forced vital capacity (β=0.112; 95%CI:0.015;0.209). Furthermore, the analyses of the association between active periods and lung function gain showed a significant trend for boys, with a dose-response effect. It was also observed that boys who were only active at 11 age years had greater lung function gains than the never-active boys. On the other hand, boys who were only active at age 15 years did not have higher gains in lung function than never-active boys. No significant associations were found for girls. CONCLUSIONS: Physical activity in early adolescence is associated with lung function gain by the end of adolescence among boys.

Mothers and Fathers Both Matter: The Positive Influence of Parental Physical Activity Modelling on Children's Leisure-Time Physical Activity.

To investigate associations between maternal and paternal sport participation, and children's leisure-time physical activity, and to explore differences by child gender. The sample comprised 737 year five students (mean age: 11.0 ± 0.6 years, 52% male) recruited through the Fit for Pisa Project which was conducted in 2008 at 6 secondary schools in Goettingen, Germany. Maternal and paternal sport participation were assessed through child reports of mothers' and fathers' weekly participation in sport. Children's leisure-time physical activity was measured as minutes/week that children engaged in organized and nonorganized sport. Multiple linear regression was used to assess associations between maternal and paternal sport participation, and children's leisure-time physical activity. Both maternal and paternal sport participation were positively associated with children's leisure-time physical activity (maternal: b = 34.20, p < .001; paternal: b = 25.32, p < .05). When stratifying analyses by child gender, maternal sport participation remained significantly associated with leisure-time physical activity in girls (b = 60.64, p < .001). In contrast, paternal sport participation remained significantly associated with leisure-time physical activity in boys (b = 43.88, p < .01). Both maternal and paternal modeling positively influence children's leisure-time physical activity.

Cardiorespiratory fitness is related to metabolic risk independent of physical activity in boys but not girls from Southern Brazil.

Our aim was to determine the relationship between cardiorespiratory fitness (CRF) and metabolic risk in adolescents from Southern Brazil. We performed a school-based cross-sectional study in 1,037 adolescents (436 boys) aged 10-16 years from Londrina, PR, Brazil. CRF was determined by 20-m shuttle run test. A continuous metabolic risk score was obtained from the mean of fasting glucose, triglycerides, high density lipoprotein, blood pressure, and waist circumference z-scores. Age, physical activity (Baecke questionnaire), body mass index (BMI; weight/stature(2) ), and somatic maturity (Mirwald method) were included as covariates in multiple linear regression analyses. CRF was related to metabolic risk in boys (β = -0.02, P < 0.01) and girls (β = -0.01, P = 0.02) after adjusting for chronological age, BMI, and somatic maturity. However, when adjusted for physical activity, CRF failed to explain metabolic risk in girls (β = -0.01, P = 0.24). We conclude that CRF is independently and inversely related to metabolic risk in boys, but physical activity either mediates or confounds the association between CRF and metabolic risk in girls. Am. J. Hum. Biol. 28:534-538, 2016. © 2016 Wiley Periodicals, Inc.

Localization of Physical Activity in Primary School Children Using Accelerometry and Global Positioning System

BackgroundEcological approaches have highlighted the importance of the built environment as a factor affecting physical activity. However, knowledge on children’s activity patterns is still incomplete. Particularly, data on the spatial context of physical activity is limited, which limits the potential to design location-based interventions effectively. Using global positioning system (GPS) and accelerometry, this study aimed to identify locations where children engage in moderate-vigorous physical activity (MVPA).MethodsParticipants included 119 children (11–14 years, 57% girls) from public schools in Winterthur, Switzerland. During a regular school week between February and April 2013, children wore an accelerometer and GPS sensor for seven consecutive days. Time-matched accelerometer and GPS data was mapped with a geographic information system and each data point was assigned to one of seven defined activity settings. Both the absolute amount of MVPA and proportion of time in MVPA were calculated for every setting. Multilevel analyses accounting for the hierarchical structure of the data were conducted to investigate any gender differences.ResultsChildren achieved most MVPA on streets (34.5%) and on school grounds (33.4%). The proportion children spent in MVPA was highest in recreational facilities (19.4%), at other schools (19.2%) and on streets (18.6%). Boys accumulated significantly more MVPA overall and on other school grounds (p < 0.05) and showed a significantly higher proportion of time in MVPA at own school and outside of Winterthur (p < 0.05).ConclusionsThe results indicate the importance of streets and school grounds as activity-promoting environments. The high use of streets may be an indicator for active transportation, which appears to contribute to an active lifestyle in both genders. In contrast, the school setting is more likely to encourage physical activity in boys. Recreational facilities seem to be conducive for MVPA among both genders, although infrequently visited during the week of measurement.

G.P.394 - Physical activity in boys with DMD is lower and less demanding compared to healthy boys

G.P.394 - Physical activity in boys with DMD is lower and less demanding compared to healthy boys

Relationship of physical activity and sedentarism with tobacco and alcohol consumption, and Mediterranean diet in Spanish teenagers.

This study examined the association of physical activity and sedentarism with tobacco and alcohol consumption, and adherence to the Mediterranean diet in teenagers of both genders. A total number of 1897 Spanish teenagers (12-16 year-olds) took part in the present cross-sectional study. The variables were measured by means of questionnaires previously validated for these ages. Physical activity was positively associated to the degree of adherence to the Mediterranean diet for both genders (ß = .144, P < .001 for boys and ß = .066, P< .05 for girls), and inversely associated to smoking for boys (ß = -.135, P = <.001). Sedentary behaviors for leisure purposes (TV and PC) were negatively associated to adherence to the Mediterranean diet for both boys (ß =-.100 and ß = -.104, both P < .05, respectively) and girls (ß= -.148 and ß = -.141, both P <.001), and positively associated to alcohol consumption for girls (ß = .114, P < .01 and ß = .199, P < .001, respectively). results suggest that physical activity and sedentary behaviors have an important relationship with the adherence to the Mediterranean diet in teenagers. Also, higher levels of physical activity in boys can lead to reduced tobacco use, while watching TV and PC leisure can lead to increased alcohol consumption in girls.

Daylight saving time as a potential public health intervention: an observational study of evening daylight and objectively-measured physical activity among 23,000 children from 9 countries

BackgroundIt has been proposed that introducing daylight saving measures could increase children’s physical activity, but there exists little research on this issue. This study therefore examined associations between time of sunset and activity levels, including using the bi-annual ‘changing of the clocks’ as a natural experiment.Methods23,188 children aged 5–16 years from 15 studies in nine countries were brought together in the International Children’s Accelerometry Database. 439 of these children were of particular interest for our analyses as they contributed data both immediately before and after the clocks changed. All children provided objectively-measured physical activity data from Actigraph accelerometers, and we used their average physical activity level (accelerometer counts per minute) as our primary outcome. Date of accelerometer data collection was matched to time of sunset, and to weather characteristics including daily precipitation, humidity, wind speed and temperature.ResultsAdjusting for child and weather covariates, we found that longer evening daylight was independently associated with a small increase in daily physical activity. Consistent with a causal interpretation, the magnitude of these associations was largest in the late afternoon and early evening and these associations were also evident when comparing the same child just before and just after the clocks changed. These associations were, however, only consistently observed in the five mainland European, four English and two Australian samples (adjusted, pooled effect sizes 0.03-0.07 standard deviations per hour of additional evening daylight). In some settings there was some evidence of larger associations between daylength and physical activity in boys. There was no evidence of interactions with weight status or maternal education, and inconsistent findings for interactions with age.ConclusionsIn Europe and Australia, evening daylight seems to play a causal role in increasing children’s activity in a relatively equitable manner. Although the average increase in activity is small in absolute terms, these increases apply across all children in a population. Moreover, these small effect sizes actually compare relatively favourably with the typical effect of intensive, individual-level interventions. We therefore conclude that, by shifting the physical activity mean of the entire population, the introduction of additional daylight saving measures could yield worthwhile public health benefits.Electronic supplementary materialThe online version of this article (doi:10.1186/1479-5868-11-84) contains supplementary material, which is available to authorized users.

Association of environment and policy characteristics on children's moderate-to-vigorous physical activity and time spent sedentary in afterschool programs

BackgroundAfterschool programs are an important setting in which to promote children's physical activity. This study examines the association of environmental and policy characteristics on the moderate-to-vigorous physical activity and sedentary behavior of children attending afterschool programs. MethodsA total of 1302 children attending 20 afterschool programs across South Carolina wore accelerometers (ActiGraph GT3X+) for up to 4non-consecutivedays. Policy-level characteristics were evaluated using the Healthy Afterschool Program Index-Physical Activity scale. Physical activity space was measured using a measuring wheel (indoor, ft2) and Geographical Information Systems software (outdoor, acres). The structure (free-play or organized) of activity opportunities was evaluated via direct observation. Time spent in moderate-to-vigorous physical activity and sedentary, both indoors and outdoors, was estimated using accelerometry. ResultsFor every 5000ft2 of utilized indoor activity space an additional 2.4 and 3.3min/day of sedentary behavior was observed among boys and girls, respectively. A higher ratio of free-play to organized play was associated with higher indoor sedentary behavior among boys and girls (3.9min/day and 10.0min/day, respectively). For every 1acre of outdoor activity space used, an additional 2.7min/day of moderate-to-vigorous physical activity was observed for boys. A higher free-play to organized play ratio was associated with higher outdoor moderate-to-vigorous physical activity for boys and girls (4.4 and 3.4min/day increase, respectively). Policy characteristics were unrelated to moderate-to-vigorous physical activity levels and time spent sedentary. ConclusionFindings indicate that policies and size of activity space had limited influence on moderate-to-vigorous physical activity and sedentary behavior, suggesting that a programmatic structure may be a more effective option to improve moderate-to-vigorous physical activity levels of children attending afterschool programs.

Adolescents' physical activities and peer norms: the mediating role of self-efficacy.

The purpose of the present study was to examine the relations among adolescents' self-efficacy and social norms, and physical activity and whether self-efficacy mediated the relationship between social norms and physical activity. 400 junior high school students (202 boys, 198 girls, 2 not identified; M age = 15.3yr., SD = 0.6) completed a demographic questionnaire, the International Physical Activity Questionnaire (IPAQ), the Perceived Self-Efficacy in Physical Activity Scale, and the Physical Activity Social Norms Scale. Regression analyses indicated that both self-efficacy and social norms predicted physical activity. Self-efficacy fully mediated the relationship between peer norms and physical activity for boys but partially mediated the relationship for girls. An application of the results may be to foster self-efficacy and peer norms as a motivational strategy for supporting increased physical activity.

Association of physical activity in childhood and early adulthood with carotid artery elasticity 21 years later: the cardiovascular risk in Young Finns Study.

BackgroundDecreased arterial elasticity is a risk factor for several cardiovascular outcomes. Longitudinal data on the effect of physical activity in youth on adult arterial elasticity are limited. The aim of this study was to determine the long‐term effects of physical activity in children and young adults on carotid artery elasticity after 21 years of follow‐up.Methods and ResultsParticipants were 1417 children (aged 9 to 15 years) and 999 young adults (aged 18 to 24 years) from the prospective Cardiovascular Risk in Young Finns Study. Participants had questionnaire measures of leisure‐time physical activity available from 1986 and ultrasound‐derived indices of carotid artery elasticity measured in 2007. Carotid artery elasticity indices were distensibility (%/10 mm Hg), Young's elastic modulus (kPa), and stiffness index (unitless). Physical activity at age 18 to 24 years was directly associated with distensibility (β=0.068, P=0.014) and inversely with Young's elastic modulus (β=−0.057, P=0.0037) and indirectly with stiffness index (β=−0.050, P=0.0028) 21 years later in males and females. The associations remained after adjustment for age, sex, body mass index, smoking, systolic blood pressure, serum lipids and insulin, and 21‐year change in physical activity. At age 9 to 15 years, the favorable association, remaining after adjustment, was found in males (distensibility [β=0.097, P=0.010], Young's elastic modulus [β=−0.060, P=0.028], and stiffness index [β=−0.062, P=0.007]) but not in females (P=0.70, P=0.85, and P=0.91, respectively).ConclusionsLeisure‐time physical activity in boys and young adults is associated with carotid artery elasticity later in life, suggesting that higher levels of physical activity in youth may benefit future cardiovascular health.

Effect of elevated physical activity on changes in body composition and subcutaneous fat distribution in boys aged 10 to 16 years: a longitudinal study

The study is aimed at evaluation of the effect of regular physical activity on total and subcutaneous body fat and its distribution in boys aged 10 to 16 years. A three-year longitudinal study was carried out in order to monitor physical development in 237 boys from sports schools and regular schools in Warsaw, Poland. The boys were selected so that their rate of puberty changes was similar based on evaluation of voice and facial hair. The authors measured 5 skinfolds in the following sites: triceps, calf, subscapular, suprailiac, and abdominal skinfolds. The percentage fraction of total body fat in body mass was measured by means of Tanita TBF 300 electronic body composition analyser. A limb fat to trunk fat ratio (LF/TF) was also calculated in order to evaluate the type of distribution of subcutaneous fat in boys and monitor its changes as affected by regular high physical activity throughout puberty. Lower total body fat and subcutaneous fat in boys from sports schools was the effect of considerably higher physical activity. It was demonstrated that with some minimal values of total body fat and subcutaneous fat, physical activity did not cause a reduction in body fat. It was found that elevated physical activity in boys is conducive to development of a more limb-oriented (peripheral) fatness, which is more favourable to human health.

Strength Training and Physical Activity in Boys: a Randomized Trial

In developed societies levels of daily physical activity (PA) among school-age children are decreasing. This implies risk factors for cardiovascular and metabolic diseases. Specific strategies to improve levels of PA are needed. In prepubertal boys there is evidence that strength training increases spontaneous PA outside of training. A total of 102 schoolchildren (age 10-14 years) in Switzerland were randomly assigned to physical education classes or to participate twice weekly at a guided strength training program for 19 weeks. Spontaneous PA energy expenditure (PAEE; 3axial accelerometry for 7 days), leg and arm strength, and body composition (dual energy radiograph absorptiometry) were measured at baseline, after 19 weeks of training intervention, and after 3 months of washout. There were no significant differences between the groups at baseline. In the intervention group, PAEE increased by 10% from baseline to end of training in boys (P = .02), but not in girls. Leg and arm strength were increased owing to training intervention in both boys and girls. All other variables were unchanged. Baseline PAEE was significantly negatively correlated with changes of PAEE. Targeted strength training significantly increases daily spontaneous PA behavior in boys. The less active children showed the greatest increase in spontaneous PAEE. Girls showed a similar increase in strength, but not in spontaneous PAEE. This may be explained by their earlier pubertal development. Strength training may be a promising strategy in schools to counteract decreasing levels of PA.

Objectively measured activity in 8–10‐year‐old Turkish children: Relationship to health‐related fitness

No objective data regarding the physical activity (PA) levels of young Turkish children currently exist. Furthermore, whether habitual PA is associated with the components of health-related fitness among children is unclear. The aim of this study was to evaluate the patterns and levels of objectively measured PA in prepubertal Turkish children and its relationship with body fatness, aerobic and anaerobic fitness. Eighty-nine 8-10-year-old children (47 boys and 42 girls) participated in this study. The intensity, duration and frequency of PA were assessed from 4 days of heart rate monitoring with 15 s sampling intervals. Body fatness was determined by measuring skinfold thickness. Anaerobic fitness was evaluated using the Wingate test. All the children performed the shuttle run test to assess aerobic fitness. The PA of boys was significantly higher than that of girls (P < 0.05). Gender difference is more marked for vigorous PA. Instead of sustained PA, short bouts of PA, lasting up to 1 min, were characteristic of PA patterns of children. The duration and frequency of PA were positively related to aerobic fitness and negatively related to fatness for both gender groups (P < 0.05). These relationships were more prominent for accumulated PA than for other measures of PA. No relationship was obtained between PA and anaerobic fitness in either gender group (P > 0.05). Intermittent, accumulated moderate intensity PA may be more important than sustained vigorous intensity PA in influencing children's fitness and fatness levels. Detailed studies are needed to clarify which dimension of PA is more beneficial for health-related fitness in children.

Educação física escolar, atividade desportiva e atividade física total em adolescentes

Less than half of adolescents reach the recommended300 minutes per week of physical activity (PA). Physical educationclasses and sports participation provideopportunities for adolescents to accumulate moretime for PA practice; however, littleis known about the influence of these variables onthe level of total physical activity ofadolescents. The aim of this study was toinvestigate the association between the practiceof physical education (PE) in schools and sportsactivities (SA) with the practice oftotal PA of adolescents. The study wascross-sectional and involved 467 adolescents ofhigh school (15.8 ± 0.9 years-old) from the city ofRio Claro, in the State of São Paulo. Participants completed the Physical ActivityQuestionnaire to Older Children (PAQ-C)and questions related to the practice of PE and SAin schools. We performed a logisticregression with p&lt;0.05 using SPSS. Girls hadlower prevalence of PA than boys, 9.4% and26.8%, respectively. Boys who did not participateof PE classes (OR=0.25, CI95%=0.09-0.66) and SA in schools (OR=0.34, CI95%=0.12-0.95)were less likely to be active in PAthan boys who practiced these activities. Theparticipation in PE classes or engagementin some SA were positively associated with thepractice of total PA in boys.

The impact of physical education on obesity among elementary school children

In response to the dramatic rise in childhood obesity, the Centers for Disease Control (CDC) and other organizations have advocated increasing the amount of time that elementary school children spend in physical education (PE) classes. However, little is known about the effect of PE on child weight. This paper measures that effect by instrumenting for child PE time with the state's mandated minimum number of minutes of PE, using data from the Early Childhood Longitudinal Study, Kindergarten Cohort (ECLS-K) for 1998–2004. Results from IV models indicate that PE lowers BMI z-score and reduces the probability of obesity among 5th graders. This effect is concentrated among boys; we find evidence that this gender difference is partly attributable to PE being a complement with other physical activity for boys, whereas they are substitutes for girls. This represents some of the first evidence of a causal effect of PE on youth obesity, and thus offers at least some support for the assumptions behind the CDC recommendations. We find no evidence that increased PE time crowds out time in academic courses or has spillovers to achievement test scores.

Associations between Neuromuscular Function and Levels of Physical Activity Differ for Boys and Girls during Puberty

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. 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. 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. 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.