Physical Fitness In Boys Research Articles

Longitudinal pathways of associations between motor proficiency and physical fitness during earlier and later childhood: The NW-CHILD study.

Understanding the relationships between motor proficiency (MP) and physical fitness (PF) is important for the future health of children, although longitudinal findings of this nature are limited. This study explored the association between MP and PF during earlier childhood (6 and 9 years old) and later childhood (12 years old) in boys and girls. A stratified and randomized research design including a baseline and two follow-up time-point measures (2010, 2013, and 2016) were used. Primary school children (N = 374, boys = 178; girls = 196) were tested with the Bruininks-Oseretsky Test of Motor-Proficiency-2, Short Form, and the Test of Gross Motor Development- 2, at ages 6 and 9 years, and with the Progressive Aerobic Cardiovascular Endurance Run test at age 12. Spearman Rank Order Correlations and stepwise regression analyses were used to analyze the data. Although of a low magnitude, proof of a dynamic longitudinal, but a stable relationship between MP and PF were found and with different gender-specific relationships in this pathway of association. A small but significant percentage of variation in PF at 12 years could be explained by overall motor competence (MC) and object control skills (OCS) at the ages of 6 and 9 years. Among girls, the association with PF at 12 years was influenced by both OCS, and MC, although only MC contributed to the variation found in boys. Socio-economic status made an insignificant contribution at 6 years to later PF in boys, but not in girls. MC, including OCS during early and middle childhood can be considered as possible triggers of physical activity which again, can increase PF during later childhood. Obtaining early competence in these developmental areas is therefore important to promote positive and sustainable trajectories of health with long-term health outcomes.

Associations between Dietary Patterns and Physical Activity with Physical Fitness among Adolescents in Shandong Province, China: A Cross-Sectional Study

The trend of physical fitness (PF) and physical activity (PA) among Chinese adolescents is not optimistic, and unhealthy dietary behaviors are common. PA and dietary patterns (DPs) have been linked to PF in adolescents, but the associations between DPs and PF with PF in Chinese adolescents are rarely discussed. A total of 8796 adolescents aged 11-18 were enrolled from Shandong Province, China. The CNSPFS battery was applied to assess PF. PA levels and diet quality were determined using the Physical Activity Questionnaire for Adolescents and the modified Chinese Diet Quality Questionnaire, respectively. This study used factor analysis to identify DPs and linear regression models to investigate the association between PF and related factors. The average PF score of the participants was 75.67. Adolescents who were girls, lived in rural areas and were active in PA performed better on the PF test (p < 0.05). Boys whose fathers were university educated or above had a higher probability of achieving higher PF scores (OR 4.36, 95% CI 1.32-14.36); however, if their mothers were university educated or above, they had a lower probability of achieving higher PF scores (OR 0.22, 95% CI 0.063-0.76). Unhealthy dietary pattern was negatively correlated with cardiorespiratory fitness in boys (OR 0.56, 95% CI 0.31-0.98). The association between unhealthy dietary pattern and girls' BMI became significant after adjustment for PA (p < 0.05). Girls performed better in PF than boys. Highly educated fathers could contribute to improve the PF performance in boys. There were four DPs among adolescents in Shandong Province, and different DPs may have different effects on PF in boys and girls.

Inequalities in the association between adherence to the Mediterranean diet and physical fitness in the young population during the COVID-19 lockdown.

Objective: this study analyzed the association between adherence to the Mediterranean diet and proxy-reported physical fitness among Spanish and Brazilian youths during the COVID-19 lockdown according to several inequality indicators. Methods: we conducted a cross-sectional study with parents and guardians of children and adolescents from Spain and Brazil. The evaluation process was through the use of online questionnaires. Adherence to the Mediterranean diet was assessed using the Mediterranean Diet Quality Index in Children and Adolescents. Proxy-reported physical fitness was determined using the International Fitness Scale. Inequality indicators (gender, nationality, socioeconomic status, and parents/guardians' education level) were evaluated with a survey completed by the participants' parents/guardians. Binary logistic regression models estimated the association between adherence to the Mediterranean diet and proxy-reported physical fitness, with stratification according to inequality variables. A total sample of 1,099 Spanish and Brazilian individuals (47.6% girls, aged 3 to 17 years) were included in the analysis. Results: compared to the "improvement needed to Mediterranean diet" category, the "optimal Mediterranean diet" group was significantly associated with "very good" physical fitness in boys (OR = 1.5; 95 % CI: 1.0-2.1) and in participants with parents/legal guardians' education level without university studies (OR = 1.5; 95 % CI: 1.0-2.4). Conclusions: gender and parents/guardians' education level plays a significant role in the association between the "optimal Mediterranean Diet" and "very good" physical fitness level in Spanish and Brazilian children and adolescents. Future prospective studies are needed to investigate the role of inequality indicators in this relationship.

Physical fitness in children and adolescents categorized by fat mass level

To evaluate the relationship between fat mass with anthropome tric indicators and, secondly, to compare the performance of physical fitness among children and adolescents categorized with adequate and excess fat mass. A descriptive cross-sectional study was conducted with 863 schoolchildren aged 6 to 17.9 years. Weight, height, and waist circumference were measured. physical fitness [speed (20m), agility (10x5m), and ho rizontal jump] was evaluated. Fat mass was calculated by anthropometric equation, body mass index, ponderal index, and waist to height ratio. Data were grouped into 6 age groups. Children of both sexes categorized as having adequate levels of fat mass had lower values of body mass index, ponderal index, and waist to height ratio than children with high levels of fat mass. In physical fitness, children with adequate fat mass were better than the ones with elevated fat mass. In girls with adequate fat mass, better results were observed in horizontal jump and agility during adolescence. There were no differences in the speed test. Fat mass can be considered as a valuable tool for determining excess body fat and categorizing children and adolescents with adequate and excess fat mass. In addition, having acceptable levels of fat mass may contribute to better physical fitness in boys in horizontal jump, agility, and speed and, in girls, only in horizontal jump and agility.

Adolescents with Higher Cognitive and Affective Domains of Physical Literacy Possess Better Physical Fitness: The Importance of Developing the Concept of Physical Literacy in High Schools.

Physical literacy (PL) is thought to facilitate engagement in physical activity, which could lead to better physical fitness (PF). The aim of this study was to examine the reliability of the Croatian version of two frequently applied PL questionnaires that evaluate knowledge and understanding, perceived competence, environment, and value for literacy, numeracy, and PL and validity regarding correlation with objectively evaluated PF in adolescents. Five hundred forty-four high school students (403 females, 141 males) from Croatia were tested on PF (standing long jump, sit-ups for 30 s, sit-and-reach test, multilevel endurance test) and two PL questionnaires. The reliability of the Croatian version of the Canadian Assessment of Physical Literacy knowledge and understanding (CAPL-2-KU) and PLAYself was good (α = 0.71–0.81 for PLAYself subscales, κ = 0.39–0.69 for CAPL-2-KU). Genders differed in the self-description dimension of PLAYself, with higher results in boys (Z = 3.72, p < 0.001). CAPL-2-KU and PLAYself total score were associated with PF in boys and girls, with PLAYself having stronger associations with PF. This research supports the idea of PL as an essential determinant for the development of PF, highlighting the necessity of the development of cognitive and affective domains of PL in physical education throughout a specifically tailored pedagogical process.

Physical Fitness in Preschool Children

Introduction. The level of mental and motor development as well as physical fitness and perceptual-motor performance should guarantee success in adapting to the new school environment.&#x0D; The aim of the research. The aim of the research was to determine physical fitness in preschool children of both genders aged from 4 to 7 years.&#x0D; Material and methods. The study included 275 children at the chronological age of 4 to 7 years including 134 girls and 141 boys. In order to assess physical fitness, the authors used the Wrocław Physical Fitness Test for preschool children completed by the endurance test&#x0D; Results. Final physical fitness results showed that six-year-old boys were the fittest and less fit were girls at the age of seven. The least fit were boys and girls at the age of four. &#x0D; Conclusions&#x0D; The Wrocław Physical Fitness Test and the endurance test revealed that the experimental group of children aged between four and seven years from the Western Pomerania region represented a satisfactory physical fitness level. It should be noted that this level was significantly lower than the ones obtained in tests conducted by other authors in 2006, 1996, 1972, and 1967.&#x0D; The represented fitness level, especially the level of endurance, may result in adaptation disorders during the school shock period.&#x0D; The phenomenon of sexual dimorphism at preschool age is demonstrated by significantly better physical fitness in boys at the age of five and six and balanced fitness at the age of seven.&#x0D; Positive development of physical fitness is not supported by ongoing lifestyle pre-orientation. It is recommended to complete primary school admission criteria for the first form by physical fitness standards, including endurance.

Profiling children longitudinally: A three-year follow-up study of perceived and actual motor competence and physical fitness.

Longitudinal designs enhance our understanding of children's development and its influence on movement behaviors and health. This three-year follow-up study aimed to develop profiles according to perceived and actual motor competence (MC) (locomotion, object control, and overall) and physical fitness in boys and girls longitudinally including children's temporal migrations among clusters in terms of profiling trends. A secondary aim was to compare physical activity participation and weight status at each time point according to these profiles. One hundred and four typically developing Spanish children (45.8% girls) between 4 and 9years old at baseline participated in this study. Data were collected at three time points one year apart, between January 2016 and May 2018. A self-organizing map and K-means cluster analysis were used to classify and visualize the values and temporal trajectories longitudinally. The study of the profiles in three consecutive years revealed five profiles, three for boys [ie, profile 1 (aligned-high), profile 2 (aligned-partially-low perception-medium actual MC and fitness), and profile 3 (non-aligned-medium perception-low actual MC and fitness)]; and two for girls [ie, profile 4 (aligned-high) and profile 5 (aligned-low)]. For highly perceived and capable children, boys (profile 1) and girls (profile 4), there was a tendency for higher physical activity participation and lower body mass index and waist circumference over time compared to their counterparts who had medium and/or low levels in perception and actual MC and fitness (P<.05). As children age, those with low values in perceived and actual MC and fitness in object control skills will present a higher probability of maintaining unhealthy lifestyles. So, prior intervention, children's profiles identification should be analyzed according to the type of MC.

Secular Trends of Physical Fitness in Twenty-Five Birth Cohorts of Slovenian Children: A Population-Based Study.

In Slovenia, the national SLOfit surveillance system of the somatic and motor development of children and youth has been enabling researchers to observe the developmental trends of the entire population of school-aged children since 1987. The national database currently incorporates over 7.2 million sets of measurements of eight fitness tests and three anthropometric measurements. Since 1991, as in the rest of the world, in Slovenia, there is a common perception that the physical fitness of contemporary children is in decline and below the level of the physical fitness of the previous generation's childhood fitness. Our paper examines the trends of physical fitness in 26 birth cohorts of 7–10-year-olds. The analysis shows that the secular trends of physical fitness in boys and especially in girls have been positive and that the level of physical fitness of recent birth cohorts exceeds the national average of physical fitness of the 1989–2019 period. At the same time, the analysis reveals that the distribution of physical fitness has been changing from almost normal in the cohorts born in the first half of the 1980s, toward positively skewed in the subsequent cohorts born before the year 2000, and bimodal distribution in the later cohorts, indicating growing inequality and polarization of the motor development of children.

The associations between digit ratio, aerobic fitness, physical skills, and overall physical fitness of elite youth distance runners

Lower digit ratios between the lengths of fingers 2 (2D) and 4 (4D) (2D:4D) are associated with superior distance running and athletic performance. We examined relationships between 2D:4D, aerobic fitness, physical skills, and overall physical fitness of elite adolescent boy and girl distance runners. Subjects were top five finishers for their sex and age in 10 or more races of 10 km or longer in Michigan in 1981. We calculated 2D:4D of 15 girls and 11 boys from radiographs. Subject peak O2 consumption (VO2Peak ), ventilatory threshold (VT), and point of equivalent change (PEC) were collected during intermittent treadmill protocol tests. Performances on physical skills tests (flex-arm hang, broad jump, vertical jump, figure-8-run, sit ups, and sit-and-reach test) were collected in the laboratory. We examined the interrelationships between 2D:4D, subject sex, aerobic fitness, physical skills test performance, and overall physical fitness, a composite of aerobic and physical skills performance with correlation, linear regression, t tests, and principle component analyses. Girls had significantly larger right hand (R) 2D:4D than boys. Boys had greater VO2Peak by mass than girls. Boys with lower R2D:4D had significantly greater VO2Peak and PEC. Girls with lower R2D:4D had significantly greater VT. Factors associated with aerobic fitness explained most of the variation in composite physical fitness scores. Composite aerobic fitness, physical skills, and overall physical fitness scores of boys were negatively correlated with R2D:4D. These data suggest that R2D:4D may help predict distance running performance in girls and boys and overall physical fitness in boys and provide additional insights into the innate factors influencing youth physical fitness.

Associations between Daily Step Counts and Physical Fitness in Preschool Children

Purpose: To investigate the relationships between daily step counts and physical fitness in preschool children. Methods: Preschoolers’ step counts were assessed by ActiGraph accelerometers consecutively for seven days. Physical fitness was assessed by a 20 m shuttle run test (cardiorespiratory fitness), the handgrip and standing long jump tests (musculoskeletal fitness), and the 2 × 10 m shuttle run test (speed/agility). A composite score was created from the mean of the standardized values of all physical fitness tests. Results: A total of 301 preschoolers (134 girls, mean age 57.40 ± 5.47 months; 167 boys, mean age 58.10 ± 5.34 months) were included in the final analysis. Compared with the lowest tertile, boys and girls in the highest tertile of step counts achieved high physical fitness with odds ratio (OR) being 5.39 (95% CI = 1.65–17.59) and 4.42 (95% CI = 1.30–14.99), respectively, after adjusting for confounders. Meanwhile, a relationship was observed for each 1000 steps/day increment being associated with 43% (OR = 1.43, 95% CI = 1.10–1.85) and 62% (OR = 1.62, 95% CI = 1.20–2.19) increment for high physical fitness in boys and girls, respectively. In addition, significant non-linear relationship was observed between daily steps and physical fitness in boys, which indicated that accumulated 8000 steps/day was associated with the highest ratio to achieve high physical fitness. Conclusions: Positive relationships between step counts and physical fitness were observed in preschool children, and the relationships were strongest for those who accumulated 8000 steps/day in boys. To confirm the findings in this study, well-designed and large-scale longitudinal studies are needed in the future.

FEATURES OF PHYSICAL DEVELOPMENT AND PHYSICAL FITNESS IN BOYS WITH HEARING IMPAIRMENTS AND THEIR CORRECTION USING SPORTS GYMNASTICS

Aim. The article deals with a possible correction of physical development and physical fitness in boys with hearing impairments with the help of sports gymnastics. Materials and methods. Boys aged 7–9 years were divided into two groups – experimental and control – 25 persons in each group. In the control group, the lessons were conducted following a standard program. In the experimental group, the lessons followed the program of sports gymnastics. In both groups, the training course lasted six months. Testing was conducted at the beginning and the end of the study. Results. After the experiment, the results of the experimental group exceed those of the control group. Conclusion. Regular lessons made according to a sports gymnastics program allow improving physical development and physical fitness in boys with hearing impairments aged 7–9 years.

Physical Fitness across 11- to 17-Year-Old Adolescents: A Cross-Sectional Study in 2267 Austrian Middle- and High-School Students

Puberty is a critical period in the development of physical fitness. The purpose of this study, therefore, was to examine the development of various components of physical fitness in Austrian adolescents between 11 and 17 years of age. A total of 2267 (51% male) adolescents from 18 secondary schools in Western Austria provided valid data. Following anthropometric measurements, participants performed the German motor test, which consists of 8 test items that assess speed, power, strength, endurance, agility, balance, and flexibility. Differences in physical fitness by age and sex were examined via a 2 by 7 MANOVA. In general, fitness improved between the ages 11 and 13 years in boys and girls. After the age of 13, physical fitness remained relatively stable in girls, while there was a continuous increase in physical fitness in boys, except for flexibility, which remained stable. Accordingly, boys performed better than girls, except for flexibility, which was better in girls. No sex difference occurred for balance. Biological changes (e.g. changes in sex hormones, body composition), contribute to significant gains in strength and endurance throughout adolescence, particularly in boys. In girls, increases in physical fitness were less pronounced and were generally limited after the age of 13. This may also reflect behavioral changes and emphasizes the importance of continued promotion of physical activity and sports, particularly in girls.

Relationships among fitness, obesity, screen time and academic achievement in Japanese adolescents

PurposeStudents who study intensively in one of Japan's ‘cram schools’ and/or spend excess time on electronic devices such as video games are in a sedentary state much of the time, and this may affect their physical fitness. We investigated whether there are relationships among obesity, physical fitness and academic achievement in Japanese students after controlling for socioeconomic and behavioral confounding factors. MethodsThe data of 315 students (152 females [48%], 163 males [52%]; 12–13yrs old) were analyzed. Academic achievement was assessed by the total grade points on eight school subjects (GP8). Students with a body mass index at or above the 85th percentile of each gender were classified as the overweight/obese group. Physical fitness was evaluated by the total score on eight fitness tests. Socioeconomic and behavioral confounders including the mother's educational background, household income, cram school utilization and time spent on video games/mobile phones were used as covariates. ResultsThe GP8 of the overweight/obese students was significantly lower than that of the normal weight students (27.2 vs. 29.0 points, respectively). After adjusting for the confounders, the physical fitness score was found to be a significant factor for determinants of GP8 in boys (β=0.324), but not in girls. The obesity status was a factor for GP8 in the girls (β=−0.160) but not in the boys. ConclusionThese results suggest that physical fitness in boys and obesity status in girls could be important factors not only for health status but also for academic achievement, independent of socioeconomic and behavioral backgrounds.

The relationship between digit ratio (2D:4D) and physical fitness in boys 7 to 13 years

The relationship between digit ratio (2D:4D) and physical fitness in boys 7 to 13 years

Relationship of parental health-related behaviours and physical fitness in girls and boys.

AimPhysical activity (PA) and physical fitness (PF) are known to be closely connected. Various environmental and biological constraints have been shown to influence children’s PA with parents being among strong determinants of their children’s PA behaviour. However, little is known about parental influence on PF in children. Therefore, the purpose of this study was to identify the influence of parental health-related behaviours and attitudes on PF in boys and girls.Subjects and methodsBaseline data of 1,875 primary school children (7.1 ± 0.6 years; 50 % male) were included in the analyses. Lateral jumping performance was used as a proxy for whole-body coordination and the 6-min run for cardiovascular fitness. Parental health-related behaviours, attitudes and sociodemographic variables were assessed via questionnaire. Regression analyses, adjusting for age and BMI, were performed separately for boys and girls.ResultsThe final models of the regression analyses showed that children’s age and BMI are significantly related to PF. Mothers’ self-efficacy to encourage their children to be active is significantly associated with boys’ coordination and cardiovascular fitness and girls’ coordination. Mothers’ PA affects PF in boys, not in girls. Maternal smoking has a significantly negative effect on both boys’ and girls’ cardiovascular fitness.ConclusionThis study shows that parental health-related behaviours and self-efficacy to encourage their children to be active affect children’s PF. Influencing factors, however, differ in girls and boys, and mothers seem especially influential.

The assessment of specific physical fitness of children aged 8 and 9 years participating in tennis classes using the Jindrich Hoehm test

Summary Study aim: The purpose of the study was to use the Jindrich Hoehm test to evaluate physical fitness in boys and girls aged 8 and 9 years participating in tennis classes. Material and methods: A total of 40 children divided into four sample groups participated in the study. The J. Hoehm test consisting of seven components was used to measure and assess the physical fitness of the research participants. This test is used in child and adolescent tennis training to assess specific physical fitness. Results: The actual data showed significant differences between 8-year-old boys and girls that were established based on the test components assessing lower extremity strength capacity and the agility assessment test. In the group of children aged 9, the differences between boys and girls emerged in the test assessing lower extremity strength capacity as well as the test component assessing the forehand and backhand footwork movement technique. Inasmuch as the test component assessing lower extremity strength capacity showed differences between 8- and 9-year-old boys, no test demonstrated statistically significant differences between 8- and 9-year-old girls. Based on the normalized data, 8-year-old girls are physically fitter than 8-year-old boys. In the group of 9-year-old children, the relation is reversed. The children participating in the study display a low level of physical fitness. Conclusion: The J. Hoehm test can be a useful tool for assessing the performance of tennis coaches.

Influence of extracurricular sport activities on body composition and physical fitness in boys: a 3-year longitudinal study

To analyse the effect of extracurricular physical activities on fat mass accumulation and physical fitness during growth in early pubertal males. Longitudinal study. A total of 42 male children (9.4+/-1.4 years, Tanner I-II and 12.7+/-1.5 years, Tanner III-IV, before and after the 3.3 years follow-up, respectively), randomly sampled from the population of Gran Canaria (Spain), 26 of them physically active (PA, at least 3 h per week during 3 years) and 16 non-physically active (non-PA). Body composition (dual-energy X-ray absorptiometry), anthropometrics (body circumferences and skinfolds) and physical fitness variables (dynamic and isometric force, anaerobic capacity and maximal aerobic power) were determined in all subjects. Both groups had comparable body sizes at the start and the end of the study. Body mass index increased with growth more in the PA than in the non-PA group (P<0.05). However, fat mass accumulation with growth was lower in the PA than in the non-PA (P<0.05). There was a positive relationship between the increment of total and trunkal fat mass, especially in non-active children (r2=0.93). In contrast, there was an inverse relationship between the total lean mass growth and the accumulation of total and regional fat mass (r=-0.37 to -0.41, all P<0.05). Physical fitness was maintained in the PA, while it worsened in the non-PA children. Without any dietary intervention, children who regularly participate in at least 3 h per week of sports activities are more protected against total and regional fat mass accumulation. They also increase their total lean and bone mass to a greater extent than children who do not participate in extracurricular sport activities. In addition, PA children maintain their physical fitness during growth, while it deteriorates in the non-PA children.

SEXUAL DIMORPHISM IN PHYSICAL FITNESS. A MULTIVARIATE STUDY

875a The purposes of this study are twofold: (1) to study the impact of body size in the sexual dimorphism of physical fitness (PF) viewed as a whole, a multidimensional trait of the subject, and (2) to identify if the map of differences in fitness of both genders changes along different age groups. The sample size comprises boys (M) and girls (F) from Maputo, Mozambique. The samples per age groups are as follows: 11 years, nM=44, nF=38; 12 years, nM=28, nF=35; 13 years, nM=42, nF=41; 14 years, nM=37, nF=19. Besides height and weight, physical fitness was assessed according to the following tests: agility run, endurance run (12′), handgrip, sit-up, sit and reach. Statistical analysis to test for differences in PF adjusted for body size was multivariate analysis of covariance (MANCOVA) followed by discriminant analysis done in SPSS. In all age groups there were differences in body weight. Exception made for 12 year olds, in all other age groups the multivariate tests showed that after adjustment for body size there are differences in PF (11years, Wilks A=0.66, F=5.44, p=0.00; 13 years, Wilks A=0.52, F=15.71, p=0.00; 14 years, Wilks A =0.52, F=16.73, p=0.00). In 12 year olds and after adjustment for body height and weight there was no significant effect of gender in PF. The mapping of gender differences over this age group is not very different as pinpointed by structural coefficients. In 11 years the importance goes for endurance run and sit-ups; in 13 years is agility run, endurance run and sit-ups; in 14 years is agility run and sit-ups. In conclusion: (1) body weight is a major determinant of gender differences in PF viewed as a whole trait of the subject; (2) adjustments for body weight marked in a similar fashion the sexual dimorphism in the age group of 11 to 14 years;(3) there was no impact of strength (handgrip) in the different mapping of PF in boys and girls; (4) in the 12 year old subjects no dimorphism was evident after size adjustment.

Physical activity, calcium intake, and bone mineral content in children in The Netherlands.

To examine the relation between physical activity, calcium intake, and bone mineral content in children. Population based, cross sectional study. Primary schools in Zoetermeer, The Netherlands. Altogether 1359 Dutch boys and girls, aged 7 to 11 years (response rate 88%). Bone mineral content was measured by quantitative roentgen microdensitometry of the midphalanx of the second digit at the diaphyseal and metaphyseal site. Maximal exercise testing, according to the Bruce treadmill protocol, was used to assess physical fitness. Habitual physical activity was assessed by use of a questionnaire on physical activities. Daily calcium intake from dairy products was estimated by use of a semiquantitative food frequency questionnaire. Bone mineral content in boys was not linearly associated with physical fitness after adjustments for differences in height, body weight, chronological age, and skeletal age. In girls a linear association was found at the metaphyseal site only. When extreme groups were compared, bone mineral content was found to be higher in "high fitness children" (upper decile) than "low fitness children" (lowest decile), with statistical significance reached in boys only. When analyses were performed in subgroups of skeletal age, a clear linear relation between physical fitness and bone mineral content was seen in the mature subgroup in both boys and girls. No linear association was found between habitual physical activity and bone mineral content, while the results in extreme groups (that is, upper versus lowest decile) and in subgroups of skeletal age were comparable to those on physical fitness in boys only. No association was found between daily calcium intake and bone mineral content in this age group. This cross sectional study in children aged 7 to 11 years suggests that an increased bone mineral content is found only in those with a high level of physical activity. This association is most pronounced in the more mature children. No evidence was found for an association between daily calcium intake and bone mineral content in childhood.

Chronological and biological age as related to physical fitness in boys 12 to 19 years.

The relative importance of skeletal age and chronological age in explaining body measurements and the relative importance of skeletal age, chronological age, height, weight, and their interactions in explaining motor fitness components are reported. Anthropometric, motor fitness, and skeletal maturity data have been collected in a mixed longitudinal study of Belgian school boys 12+/- - 19+/- years. At each age level multiple regression equations were calculated to evaluate the relative importance of the independent variables. Skeletal age was assessed by the TW2 method and the anthropometric measurements were taken following standard procedures. The motor fitness tests were selected on their factor loading and reliability in the same age range. Between 13 and 16 years a fairly high percentage of the variation in body dimensions is explained by skeletal age (+/-50% for stature). The percentage of explained variance reaches its maximum at 14-15 years. The highest percentage is found for linear dimensions and weight followed by bone width dimensions and circumferences. Triceps and calf skinfolds are not related to skeletal age. Chronological age as such does not contribute in the prediction of body measurements. The interaction between chronological age and skeletal age as such or in combination with height and/or weight have the highest predictive value except for trunk strength (leg lifting) and functional strength (bent arm hang). Except for static strength (arm pull), for which the explained variance ranged from 33% to 58%, the predictive value of body size, maturity, chronological age and their interactions is rather low, varying between 0% and 17%. As for body dimensions, the explained variance reaches its maximum for most motor tests at 14-15 years.