Objective: To describe changes in the body mass index (BMI) of nationally representative samples of young adult Polish males between 1965 and 2001, and to investigate variation in the incidence of ...underweight, overweight and obesity between 1965 and 2001 in the young adult males in the context of the socio-political transformation that occurred in Poland since 1989. Subjects: Four 10% nationwide random samples of 29-year-old Polish conscripts examined in 1965, 1986, 1995 and 2001. The conscripts were divided into four socio-occupational groups based on paternal education, occupation and degree of urbanization. Measurements: Height, weight and BMI (weight (kg)/height (m2)). Results: The proportion of overweight and underweight young adult males in the population increased between 1965 and 2001. The fraction of underweight decreased only among sons of farmers and entrepreneurs between 1986 and 1995 and then increased in all socio-occupational groups between 1995 and 2001. On the other hand, the proportion of overweight young adults gradually increased in all groups between 1965 and 2001.Conclusion: Socio-occupational position of the family is an important factor influencing underweight and overweight in young adult males. This factor apparently operates through a differential distribution of income, which influences components of lifestyle most likely associated with level of habitual physical activity and/or diet.
Problems with accurate chronological age (CA) reporting occur on a more or less regular basis in youth sports. As a result, there is increasing discussion of age verification. Use of 'bone age' or ...skeletal age (SA) for the purpose of estimating or verifying CA has been used in medicolegal contexts for many years and also in youth sport competitions. This article reviews the concept of SA, and the three most commonly used methods of assessment. Variation in SA within CA groups among male soccer players and female artistic gymnasts is evaluated relative to the use of SA as a tool for verification of CA. Corresponding data for athletes in several other sports are also summarized. Among adolescent males, a significant number of athletes will be identified as older than a CA cutoff because of advanced skeletal maturation when they in fact have a valid CA. SA assessments of soccer players are comparable to MRI assessments of epiphyseal-diaphyseal union of the distal radius in under-17 soccer players. Both protocols indicate a relatively large number of false negatives among youth players aged 15-17 years. Among adolescent females, a significant number of age-eligible artistic gymnasts will be identified as younger than the CA cutoff because of later skeletal maturation when in fact they have a valid CA. There is also the possibility of false positives-identifying gymnasts as younger than the CA cutoff because of late skeletal maturation when they have a valid CA. The risk of false negatives and false positives implies that SA is not a valid indicator of CA.
Height, mass and skeletal maturity (Fels method) were assessed in 135 elite youth soccer players aged 10.7-16.5 years (only two boys were ≪11.0 years). Sample sizes, years of training and current ...weekly training volume by two-year age groups were: 11-12 years ( n = 63), 2.6 - 1.0 years and 4.1 - 1.7 h; 13-14 years ( n = 29), 3.1 - 1.6 years and 4.5 - 1.7 h; 15-16 years ( n = 43), 4.7 - 2.4 years and 6.1 - 2.0 h. The oldest age group included membersof the national youth team.Heights and masses were compared to US reference values,and skeletal age and chronological age were contrasted. The players were also classified as late, average ('on time') and early maturers on the basis of differences between skeletal and chronological age, with the average category including boys with skeletal ages within - 1 year of chronological age. The mean heights and masses of 11- to 12-year-old soccer players equalled the US reference values, while those of players aged 13-14 and 15-16 years were slightly above the reference values. The mean skeletal age approximated mean chronological age in players aged 11-12 years (12.4 - 1.3 and 12.3 - 0.5 years, respectively), while mean skeletal age was in advance of mean chronological age in the two older groups (14.3 - 1.2 and 13.6 - 0.7 years, respectively, in 13- to 14-year-olds; 16.7 - 1.0 and 15.8 - 0.4 years, respectively, in 15- to 16-year-olds). Seven boys in the oldest age group were already skeletally mature and were not included when calculating differences between skeletal and chronological age. The proportion of late maturing boys in this sample of elite soccer players decreased with increasing chronological age. Among 11- to 12-year-old players, the percentages of late and early maturing boys were equal at 21% ( n = 13). Among 13- to 14-year-old players, the percentages of late and early maturing boys were 7% ( n = 2) and 38% ( n = 11) respectively, while among players aged 15-16 years the percentages of late and early maturing boys were 2% ( n = 1) and 65% ( n = 28) respectively. The results of this comparative analysis suggest that the sport of soccer systematically excludes late maturing boys and favours average and early maturing boys as chronological age and sport specialization increase. It is also possible that late maturing boys selectively drop-out of soccer as age and sport specialization increase.
This study examined the association between demographic age, sex, socioeconomic status (SES) and socio‐cultural father, mother, sibling physical activity (PA); peers and physical education teacher ...influences correlates and low, moderate and high levels of PA among Portuguese adolescents aged 10–18 years. A total of 3352 males and females attending basic and secondary schools, their parents and siblings were sampled across four regions of Portugal. PA was assessed with a psychometrically validated questionnaire. Multinomial logistic regression was used. Age was positively related with moderate and high PA. Boys and adolescents of high SES were more likely to participate in moderate and high PA. Adolescents were more likely to participate in high PA when theirs mother and sibling(s) also participated. Peers had a positive influence on participation in moderate and high PA, while physical education teachers did not have an influence. The results indicated that demographic and socio‐cultural correlates – in particular age, sex, SES, mother and sibling PA, and peer influence – were significantly associated with adolescent PA. These results also suggested that interventions should focus on girls and low SES adolescents who face higher risk of inactivity.
We test the empirical relation between ultraviolet color and attenuation as derived for starburst galaxies with a wide assortment of galaxy types detected by the Galaxy Evolution Explorer and find ...that it systematically overestimates the far-ultraviolet attenuation of our sample by ~0.5 mag. Our efforts to find an additional parameter that could improve the starburst reddening relation were unsuccessful. In particular, UV-Ks colors (in nonmatching apertures) show no correlation with the offset from the starburst reddening relation, suggesting either that UV-Ks colors are a poor tracer of present to past average star formation history (the ``b'' parameter) or that the intrinsic dust distribution/geometry may be responsible for moving galaxies off the correlation. It is possible to reduce the systematic overestimate of AFUV by using the linear correlation derived from our sample, which simply lowers the starburst predicted values of AFUV by 0.58 mag. The scatter, however, remains large at 0.89 mag.
This study investigated the influence of chronological (CA) and skeletal ages (SA), anthropometry, aerobic endurance and lower limb explosive strength on developmental changes in repeated-sprint ...ability (RSA) in soccer players aged 11-17 years. Participants were annually followed over 5 years, resulting in 366 measurements. Multilevel regression modelling analysed longitudinal data aligned by CA and SA (Model 1 and 2, respectively). After diagnosing for multicollinearity, it was possible to predict RSA with 2-level hierarchical models Model 1 (CA as Level 2 predictor): Log-Likelihood=1,515.29, p<0.01; Model 2 (SA as Level 2 predictor): Log-Likelihood=1,513.89, p<0.01. Estimating sum of sprints for young soccer players are given by equations: sum of sprints=84.47 - 1.82 × CA + 0.03 × CA2 - 0.05 × aerobic endurance - 0.10 × lower limb explosive strength -0.09 × fat-free mass + 0.13 × fat mass (Model 1); 73.58 - 0.43 × SA - 0.05 × aerobic endurance - 0.10 × lower limb explosive strength - 0.08 × fat-free mass - 0.45 × training experience + 0.13 × fat mass (Model 2). The models produced performance curves that may be used to estimate individual performance across adolescent years. Finally, the validity of each model was confirmed based on corresponding measurements taken on an independent cross-sectional sample.
Asymmetries in the distributions of birth dates in senior professional and youth soccer players have been interpreted as evidence for systematic discrimination against individuals born shortly before ...the cut-off date in assigning youth to specific age groups. This concept is known as the "relative age effect". The results of a longitudinal study of birth date distritubions of 2757 semi-professional and amateur senior soccer players in Belgium are presented. Records for competitive games were available in official statistics provided by the Royal Belgian Football Association. The chi-square statistic was used to examine differences between observed and expected birth date distributions. Regression analyses indicated a shift of bias when two different start dates were compared. Players born in the early part of the new age band (January to March) were over-represented compared with players born late in the new selection period (October to December). However, players with birthdays at the start of the old selection year (August) were still represented. In a retrospective analysis of 2138 players, variables indicative of match involvement, number of selections for matches, and time played were examined in relation to the relative age effect. The group of semi-professional and amateur senior soccer players born in the first quarter of the selected age band received more playing opportunities. Comparisons of birth date distributions (traditional approach to relative age effect) with match-related variables gave similar, though not entirely consistent, results. However, there were no differences for the mean number of selections and for playing minutes between players born at the start or the end of the selection year. Our findings suggest that match-based variables may provide a more reliable indication of the relative age effect in soccer.
Although different indicators of physical activity and different methods of analysis are used, it appears that physical activity tracks at low to moderate levels during adolescence, from adolescence ...into adulthood, and across various ages in adulthood. Tracking of inactivity is less often studied. Measures of performance- and health-related physical fitness (strength, flexibility, motor fitness, aerobic power) track significantly across childhood and adolescence, but correlations are low to moderate. Limited data that span adolescence into adulthood indicate somewhat higher interage correlations for flexibility, static strength, and power. Data for different periods in adulthood are not available. Presently, it is common to criticize focus on motor and sport skills in physical education and competitive sports as contrary to health and fitness goals (e.g., James, 1995; Livingstone, 1994; Simons-Morton et al., 1988). There is a need, however, to distinguish between youth or community sports and highly specialized sport for the elite. Sports activities, be they competitive or recreational, are probably the major form of physical activity during childhood and adolescence, and perhaps in young adulthood. Though low to moderate, the tracking of various activity indicators, most of which include sport participation, suggests that sport activities during childhood and youth may form the foundation for activity habits in the future.
Estimates of daily energy expenditure are important to studies of physical activity and energy balance. Objective measures are not always feasible and further research is needed to validate survey ...instruments and diaries. The study validates estimated activity energy expenditure (AEE) based on a 3‐day diary protocol relative to AEE derived from uniaxial accelerometry in adolescents, 265 girls and 227 boys (12.5–16.4 years). Participants completed the diary and wore a GT1M Actigraph accelerometer on the same days. Height and weight were measured. Correlations between protocols were significant (P<0.001) but moderate, r=0.65 in males and r=0.69 in females. The highest correlation occurred among males on Friday, r=0.74 (P<0.01). Controlling for body mass, partial correlations between protocols decreased to 0.44 and 0.35 in males and females, respectively. About 97% of the cases fell within the limits of agreement in a Bland–Altman plot. The criterion of inclusion for the accelerometer excluded 18% of the initial sample. In summary, the 3‐day diary was completed without any major problems and provided a reasonably valid alternative for assessing AEE. Concordance between methods was slightly lower for individuals with higher values of AEE.
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