Gaston Beunen

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.

Age at menarche in Flemish girls: current status and secular change in the 20th century

The age at menarche in a national sample of 4894 Flemish schoolgirls was surveyed in 1979-1980. The probit estimate of the mean age at menarche was 13.20 +/- 0.02 years (SD = 1.25 years). This estimate falls well within the range of reported ages at menarche for girls in northwestern Europe, but is slightly later than those for French-speaking girls in Belgium and in France. Status quo secular data for the 20th century indicate a decline in estimated mean ages at menarche of Flemish girls from about 14.3 years before World War II to 13.6 and 13.2 years, respectively, among girls born just before and during the war. Subsequently, mean ages at menarche of Flemish girls are fairly stable between 13.0 and 13.2 years. These secular changes are of the same magnitude as those observed in other European countries.

Aspectos genéticos da prática desportiva: - um estudo em gêmeos

Este estudo e percorrido por dois propositos fundamentais: a) apresentar, ainda que de modo breve, aspectos da metodologia de genetica quantitativa aplicados ao estudo de fenotipos de interesse dos cientistas das Ciencias do Desporto; e b) aplicar tais tecnicas e procedimentos em gemeos monozigoticos (MZ) e dizigoticos (DZ) para determinar a presenca de efeitos geneticos nos seus indices de pratica desportiva. A amostra e constituida por 104 pares de gemeos, 40 MZ e 64 DZ, cuja media de idades e 17,30 ± 5,82 e 17,86 ± 8,12, respectivamente. O indice de pratica desportiva foi obtido a partir do questionario de Baecke et alii (1982). Os procedimentos estatisticos compreendem tabelas de contingencia, correlacoes tetracoricas, taxas de concordância “probandwise” bem como ajustamento de modelos univariados gemelares. Os programas estatisticos utilizados foram o SPSS 9.0 e o Mx. Os principais resultados e conclusoes foram os seguintes: a) e evidente a presenca de forte agregacao familiar nos valores de pratica desportiva; b) estes valores sao mais fortes nos gemeos MZ do que nos gemeos DZ, e mais elevados nos meninos do que nas meninas; c) nos meninos o valor da dependencia genetica e de 82%, sendo muito reduzida a influencia do envolvimento comum e unico de cada par; d) nas meninas os resultados sao diametralmente opostos, ja que a influencia genetica e zero, e a do seu envolvimento comumente partilhado no seio da familia e de 71%. Estas diferencas de efeitos geneticos e do envolvimento nos dois sexos sugerem interpretacoes de natureza biologica e socio-culturalEste estudo e percorrido por dois propositos fundamentais: a) apresentar, ainda que de modo breve, aspectos da metodologia de genetica quantitativa aplicados ao estudo de fenotipos de interesse dos cientistas das Ciencias do Desporto; e b) aplicar tais tecnicas e procedimentos em gemeos monozigoticos (MZ) e dizigoticos (DZ) para determinar a presenca de efeitos geneticos nos seus indices de pratica desportiva. A amostra e constituida por 104 pares de gemeos, 40 MZ e 64 DZ, cuja media de idades e 17,30 ± 5,82 e 17,86 ± 8,12, respectivamente. O indice de pratica desportiva foi obtido a partir do questionario de Baecke et alii (1982). Os procedimentos estatisticos compreendem tabelas de contingencia, correlacoes tetracoricas, taxas de concordância “probandwise” bem como ajustamento de modelos univariados gemelares. Os programas estatisticos utilizados foram o SPSS 9.0 e o Mx. Os principais resultados e conclusoes foram os seguintes: a) e evidente a presenca de forte agregacao familiar nos valores de pratica desportiva; b) estes valores sao mais fortes nos gemeos MZ do que nos gemeos DZ, e mais elevados nos meninos do que nas meninas; c) nos meninos o valor da dependencia genetica e de 82%, sendo muito reduzida a influencia do envolvimento comum e unico de cada par; d) nas meninas os resultados sao diametralmente opostos, ja que a influencia genetica e zero, e a do seu envolvimento comumente partilhado no seio da familia e de 71%. Estas diferencas de efeitos geneticos e do envolvimento nos dois sexos sugerem interpretacoes de natureza biologica e socio-cultural

Skeletal maturity and body size of teenage Belgian track and field athletes.

Attained skeletal maturity (TW2 RUS method), skeletal maturity relative to chronological age, and body size of national-level Belgian track and field athletes 15 to 18 years of age were considered. Among the 47 male athletes, 29 (62%) were skeletally mature, while 15 (52%) of the 29 female athletes were skeletally mature. There appeared to be a predominance of skeletally mature individuals among male sprinters and jumpers, while a majority of female sprinters were not skeletally mature. Both skeletally mature and immature individuals were rather evenly represented in the other track and field categories, with the exception of female throwers, who were skeletally mature. Mean statures and weights of skeletally mature and immature 16-, 17-and 18-year-old male athletes did not differ significantly, though the skeletally mature tended to be heavier. In contrast, the skeletally mature female athletes, on the average, were taller and heavier than the skeletally immature, although the differences among the small groups were not statistically significant.

Valores normativos do desempenho motor de crianças e adolescentes: o estudo longitudinal-misto do Cariri

The aim of this study was: 1) to provide centile charts and reference values for a variety of motor tests and; 2) to compare the performance of children and adolescents from the Cariri-region with other national and international reference data. The total sample consists of 6.238 individuals (3.122 girls and 3.116 boys) between 8 and 17 years. The centile charts were constructed for each sex separately using the LMS method implemented in the LMSchartmaker Pro version 2.3. The reference charts of Cariri-region are similar to that observed in previously reported studies. Except for trunk lift boys outperform girls at most age levels, emphasizing the presence of sexual dimorphism. The P50 values of children and adolescents from Cariri were consistently lower than the P50-values of children and adolescents from Londrina (Brazil) and other samples from Portugal.

O tracking da atividade física: Um estudo em adolescentes do sexo masculino

The purpose of this study is to analyze the tracking of physical activity in adolescent males with a quasi-simplex model formulated in the structural covariance modeling paradigm. Data was taken from the Leuven growth study in which 588 adolescent males ‐ with ages varying from 12.76 to 17.73 ‐ had been followed during 6 years. Physical activity was evaluated by a validated questionnaire. The physical activity indicator was the amount of time spent in formal sport activity regardless of the amount of hours spent in physical education. Data was analyzed through an autoregressive quasi-simplex model that allows analysis of different tracking formulation. Vigorous methods to estimate maximum likelihood were employed. The results were: high stability of physical activity year-by-year; moderate tracking in the adolescence; and low values of intra-individual instability in the differences that occurred among the studied individuals in each point in time.