Showing papers by "Gaston Beunen published in 2004"

Growth in peak aerobic power during adolescence.

Abstract: GEITHNER, C. A., M. A. THOMIS, B. VANDEN EYNDE, H. H. M. MAES, R. J. F. LOOS, M. PEETERS, A. L. M. CLAESSENS, R. VLIETINCK, R. M. MALINA, and G. P. BEUNEN. Growth in Peak Aerobic Power during Adolescence.Med. Sci. Sports Exerc., Vol. 36, No. 9, pp. 1616 –1624, 2004. Purpose: To model the growth of peak aerobic power during adolescence in both sexes followed longitudinally from 10 to 18 yr. Methods: Peak aerobic power (peak V u O2) was measured annually during a maximal treadmill test with the Bruce protocol. Height and weight were measured semiannually. The Preece-Baines Model I growth function was used to fit curves to data for individuals with six observations for peak aerobic power to estimate age at peak velocity (PV) for peak V u O2 (age at PVPV u O2), PVPV u O2 (L·min 1 ·yr 1 ), and value at PVPV u O2 (L·min 1 ) for each individual. Curves were successfully fitted for 83 individuals (48 males, 35 females). The model was also fitted to individual data for height and weight to estimate ages at peak height velocity (PHV) and peak weight velocity (PWV). Age at PVPV u O2 was compared with ages at PHV and PWV. Pearson correlation coefficients were calculated between ages at PV and PV for peak V u O2, height, and weight. Results: Mean ages at PVPV u O2 are 12.3 1.2 yr for females and 14.1 1.2 yr for males. Peak V u O2 increases in both sexes throughout adolescence, with males having higher values than females at all ages. Age at PVPV u O2 occurs nearly coincident with PHV and before PWV in both sexes. Correlation coefficients among ages at PHV, PWV, and PVPV u O2 suggest a general maturity factor for body size and aerobic power. Conclusion: Growth in peak V u O2 exhibits a clear growth spurt in both sexes during adolescence. The growth spurt occurs earlier in females but

Exploration of myostatin polymorphisms and the angiotensin-converting enzyme insertion/deletion genotype in responses of human muscle to strength training.

Abstract: This study explores the associations between polymorphisms in two candidate genes—myostatin gene (MSTN or GDF8) and angiotensin-converting enzyme (ACE) gene—with interindividual differences in human muscle mass and strength responses to strength training. The MSTN AluI A55T (exon 1), BanII K153R, TaqI E164 K and BstNI P198A (all in exon 2) markers and the ACE insertion (I)/deletion (D) polymorphism were typed in 57 males [22.4 (3.7) years] who participated in a 10-week, high-resistance training program for the elbow flexors. Maximal strength, and maximal isometric and concentric elbow flexor torques were measured at baseline and after training. Information on muscle cross-sectional area of the upper arm was obtained by computer tomography scans. Only one individual was heterozygous for the MSTN BanII K153R variant. No allelic variant was detected at the other MSTN sites in this population. For the ACE I/D polymorphism, no evidence was found for an association of the D or I allele with baseline strength, isometric and concentric torque or arm muscle cross-sectional area [analysis of covariance (ANCOVA) 0.25

Linkage of myostatin pathway genes with knee strength in humans.

Abstract: This study was the first to explore the potential role of the myostatin (GDF8) pathway in relation to muscle strength and estimated muscle cross-sectional area in humans using linkage analysis with...

Adolescent correlates of adult physical activity: a 26-year follow-up.

Abstract: Purpose:It is hypothesized that adolescent physical activity, fitness, anthropometric dimensions, fatness, biological maturity, and family characteristics contribute to the variation in physical activity at 40 yr of age, and that these associations vary with age.Methods:Subjects were 166 mal

Determinants and Upper-Limit Heritabilities of Skeletal Muscle Mass and Strength

Abstract: Resume The purpose of this study was to estimate the genetic and environmental contribution to variation in skeletal muscle mass and strength. In addition, important determinants were analyzed by stepwise multiple regression. In a large (N = 748) sibling pair sample of young brothers, ages 24.3 ± 4.5 years, upper-limit heritabilities (t 2 ) were estimated as a propor- tion of genetic and shared environmental variability over total phenotypic variability by the variance components method in QTDT. Maximal isometric strength measures of knee, trunk, and elbow had higher t (82 to 96%) than concentric strength (63 to 87%) on Cybex isokinetic dynamometers. Indicators of muscle mass revealed very high transmissions (>90%) whereas t 2 was lower for adiposity (<70%). Stepwise regression showed that fat-free mass was the primary determinant in knee and trunk strength (partial explained variance, R = 33-45%), but a local muscularity estimate (forearm circumference) was the main covariable for el- bow strength (partial R 2 = 18-39%). In this sample neither age nor physical activity, mea- sured by the sport index of Baecke, appeared to be an important determinant of muscle mass or strength. These results show that maximal muscle strength and mass are highly transmissible and that muscle mass is the primary determinant of muscle strength.

Skeletal maturity and socio-economic status in Portuguese children and youths: the Madeira growth study.

Abstract: Background: Skeletal maturity is used to evaluate biological maturity status. Information about the association between socio-economic status (SES) and skeletal maturity is limited in Portugal.Aims: The aim of this study is to document the skeletal maturity of youths in Madeira and to evaluate variation in maturity associated with SES.Subjects and methods: The study involved 507 subjects (256 boys and 251 girls) from the Madeira Growth Study, a mixed-longitudinal study of five cohorts (8, 10, 12, 14 and 16 years of age) followed at yearly intervals over 3 years (1996–1998). A total of 1493 observations were made. Skeletal age was estimated from radiographs of the hand and wrist using the Tanner–Whitehouse 2 method (TW2). Social class rankings were based on Graffar's (1956) method. Five social rankings were subsequently grouped into three SES categories: high, average and low.Results: Median for the radius, ulna and short finger bones (RUS scores) in the total sample of boys and girls increased curvilinear...

Gene powered? Where to go from heritability (h2) in muscle strength and power?

Abstract: The importance of genetic and environmental factors in muscular strength and power variation has been reported in the last two decades. However, there is a paucity of data on gender- and age-specific estimates of heritabilities. Linkage and association studies that aim to identify genes and gene variants for muscular strength are only emerging.

Association between bone, body composition and strength in premenarcheal girls and postmenopausal women.

Abstract: Aim: The study examined whether associations between bone, body composition and strength are age dependent.Subjects and methods: Two age levels (premenarcheal girls and postmenopausal women on HRT) were studied in a 10-month follow-up. Bone, lean and fat mass were measured by dual-energy X-ray absorptiometry (DXA), and strength was measured using an isokinetic dynamometer.Results: In girls, significant correlations were found between mass (lean, fat and body mass), strength and most bone characteristics (r = 0.15–0.93). At the proximal femur changes in bone mineral density (BMD) were moderately related to changes in body composition. In the women, body mass and lean mass were significantly correlated with most bone characteristics (r = 0.34–0.82). Low to moderate correlations were observed between changes in bone and changes in body composition. After controlling for lean mass the relation between strength and bone was no longer significant.Conclusions: In premenarcheal girls, bone is partly determined by...

A quantitative trait locus on 13q14.2 for trunk strength.

Abstract: Previous findings show strong evidence for the role of retinoblastoma (Rb) in myoblast proliferation and differentiation. However, it is not known whether variation in the retinoblastoma gene (RB1 ) is responsible for normal variation in human muscle strength. Therefore, a linkage analysis for quantitative traits was performed on 329 young male siblings from 146 families with muscle strength, using a polymorphic marker in RB1 (D13S153 on 13q14.2). Trunk strength, a general strength indicator that requires activation of large muscle groups, was measured on a Cybex TEF isokinetic dynamometer. We found evidence for linkage between locus D13S153 at 13q14.2 and several measurements of trunk flexion with LOD scores between 1.62 and 2.78 (.002< p <.0002). No evidence for linkage was found with trunk extension. This first exploration of the relationship between RB1 and human muscle strength through linkage analysis warrants efforts for further fine mapping of this region.