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

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 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 curvilinearly across age whereas median for the 7 (without pisiform) carpal bones (Carpal scores) increased almost linearly. The 20-bone maturity scores demonstrated distinctive trends by gender: the medians for boys increased almost linearly while the medians for girls increased curvilinearly. SES differences were minimal. Only among children aged 10-11 years were high SES boys and girls advanced in skeletal maturity. Madeira adolescents were advanced in skeletal maturity compared with Belgian reference values.

CONCLUSION

The data suggests population variation in TW2 estimates of skeletal maturation. Skeletal maturity was not related to SES in youths from Madeira.

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

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 mass, with lean mass the most important predictor at the femoral sites. In postmenopausal women, lean mass is an important determinant of bone mineral content (BMC) and BMD, but changes in BMD are related to changes in fat. The relation between strength and BMD is mainly attributable to the relation between lean mass and BMD. The contributory effects of soft tissue to bone change over different life periods.

Sedentary behaviour, physical activity and a continuous metabolic syndrome risk score in adults

OBJECTIVE

The association of sedentary behaviour and leisure time physical activity with a validated continuous metabolic syndrome risk score was investigated in adults.

SUBJECTS/METHODS

A number of 992 adults (559 men) without cardiovascular disease or diabetes. Subjects reported time spent in leisure time physical activity and television watching/computer activities. A validated metabolic syndrome risk score, based on waist circumference, triglycerides, blood pressure, fasting plasma glucose and high-density lipoprotein cholesterol, was used. The metabolic syndrome risk score and time spent in sedentary behaviour and physical activity were analysed as continuous variables using multiple linear regression.

RESULTS

Metabolic syndrome risk was positively associated with time spent watching television/computer activities, irrespective of physical activity level, and after adjustment for age, education level, smoking status and dietary intake in women aged > or =45 years (beta=0.184, P<0.05). Independent of the time being sedentary, moderate to vigorous leisure time physical activity was inversely associated with metabolic syndrome risk in men (<45 years: beta=-0.183, P<0.01; > or =45 years: beta=-0.192, P<0.01) and women aged > or =45 years (beta=-0.203, P<0.01).

CONCLUSIONS

Although cross-sectional, the present results support inclusion of efforts to decrease sedentary behaviour in metabolic syndrome prevention strategies for women aged > or =45 years, besides promotion of moderate to vigorous physical activity, since both behavioural changes might show additional effects.

Anthropometry, carbohydrate and lipid metabolism in the East Flanders Prospective Twin Survey: heritabilities

AIMS/HYPOTHESIS

We determined the genetic contribution of 18 anthropometric and metabolic risk factors of type 2 diabetes using a young healthy twin population.

METHODS

Traits were measured in 240 monozygotic (MZ) and 138 dizygotic (DZ) twin pairs aged 18 to 34 years. Twins were recruited from the Belgian population-based East Flanders Prospective Twin Survey, which is characterised by its accurate zygosity determination and extensive collection of perinatal and placental data, including information on chorionicity. Heritability was estimated using structural equation modelling implemented in the Mx software package.

RESULTS

Intra-pair correlations of the anthropometric and metabolic characteristics did not differ between MZ monochorionic and MZ dichorionic pairs; consequently heritabilities were estimated using the classical twin approach. For body mass, BMI and fat mass, quantitative sex differences were observed; genetic variance explained 84, 85 and 81% of the total variation in men and 74, 75 and 70% in women, respectively. Heritability estimates of the waist-to-hip ratio, sum of four skinfold thicknesses and lean body mass were 70, 74 and 81%, respectively. The heritability estimates of fasting glucose, fasting insulin, homeostasis model assessment of insulin resistance and beta cell function, as well as insulin-like growth factor binding protein-1 levels were 67, 49, 48, 62 and 47%, in that order. Finally, for total cholesterol, LDL-cholesterol, HDL-cholesterol, total cholesterol:HDL-cholesterol ratio, triacylglycerol, NEFA and leptin levels, genetic factors explained 75, 78, 76, 79, 58, 37 and 53% of the total variation, respectively.

CONCLUSIONS/INTERPRETATION

Genetic factors explain the greater part of the variation in traits related to obesity, glucose intolerance/insulin resistance and dyslipidaemia.

Polymorphisms in the vitamin D receptor gene are associated with muscle strength in men and women

INTRODUCTION

Vitamin D receptor (VDR) polymorphisms have been associated with fracture risk and muscle strength, although evidence for the latter is limited and conflicting.

METHODS

BsmI, TaqI and FokI VDR polymorphisms were genotyped in 253 men (54.9 +/- 10.2 yr) and 240 women (41.5 +/- 13.2 yr). Haplotypes were constructed for BsmI and TaqI. Handgrip, isometric (at 60 degrees , 120 degrees and 180 degrees joint angle) and eccentric torques (60 degrees /s) of knee extension and flexion were analysed using AN(C)OVA. Torque-velocity curves were constructed for concentric torques at 60 degrees /s, 180 degrees /s and 240 degrees /s and analysed using multivariate AN(C)OVA. Age, height and fat-free mass were included as covariates.

RESULTS

Quadriceps isometric and concentric strength were higher in female f/f homozygotes compared to F allele carriers. Adjustment for confounding factors rendered results for quadriceps isometric strength at 120 degrees non-significant. No significant association was found with BsmI-TaqI haplotype in women. In contrast, male Bt/Bt homozygotes had higher isometric quadriceps strength at 150 degrees and higher concentric quadriceps strength than bT allele carriers without and with adjustment for confounding factors. No association was observed with FokI in men. In both genders, no interaction effect was present between BsmI-TaqI haplotype and FokI.

CONCLUSIONS

Different VDR gene polymorphisms are associated with quadriceps strength in men and women.

Somatic growth of a school-aged population from Mozambique: trend and biosocial meaning

A cross-sectional study of children and adolescents from Maputo, Mozambique, was carried out in order to (1) describe the current growth status of children and adolescents from Maputo, (2) evaluate the relative status of the growth and development of youth from Maputo compared to WHO international standards, (3) assess the relationship between socioeconomic status and growth and development, and (4) assess the impact that the civil war (1980-1992) had on the health status of children and adolescents living in Maputo. The sample is composed of 2,271 subjects (1,098 boys and 1,173 girls), age 6 to 17 years. Somatic measures included height, weight, and skinfold thicknesses from which nutritional indicators were calculated and plotted against WHO norms. Subjects were divided into three groups according to their socioeconomic status. Data from a cross-sectional study done in the same areas in 1992 was used to analyze the impact of war. Beginning at 11 years, Maputo students are always shorter and weigh less than the WHO standards. BMI in boys from 11 years and in girls from 12 years is somewhat lower than the WHO norms. A social gradient is evident, favoring those students with higher socioeconomic status. Height, weight, BMI, fat mass, and lean body mass are always higher in the 1999 sample than in the 1992 study. We conclude that (1) there is a substantial difference in height and weight values of Maputo children and adolescents compared to WHO standards; (2) there is a clear advantage of being of higher socioeconomic status; (3) socioeconomic status, hygiene, and sanitation are the main factors responsible for the greater values of the 1999 sample; and (4) differences between the stature of students with higher socioeconomic status and the WHO norms are almost irrelevant. This last aspect reveals the importance of socioeconomic factors in determining the growth process, implying its importance in facilitating the "expression" of the genotypes available in the population.

Linkage of myostatin pathway genes with knee strength in humans

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 a candidate gene approach. In young male sibs (n = 329) 11 polymorphic markers in or near 10 candidate genes from the myostatin pathway were genotyped. Muscle mass was estimated by anthropometric measurements, and maximal knee strength was evaluated using isokinetic dynamometers (Cybex NORM). Single-point nonparametric variance components and linear quantitative trait locus regression linkage analysis methods were used. Linkage patterns were observed between knee extension and flexion peak torque with markers D2S118 (GDF8), D6S1051 (CDKN1A), and D11S4138 (MYOD1), and a maximum LOD score of 2.63 (P = 0.0002) was observed with D2S118. The ratios of peak torque over muscle and bone area of the midthigh of the lower contraction velocity (60 degrees/s) showed more frequently significant LOD scores than the torques at high velocity (240 degrees/s). Although myostatin is physiologically more related to muscle mass through possible effects of hyperplasia and hypertrophy than it is to strength, only two estimated muscle cross-sectional areas were marginally linked (LOD 1.06 and 1.07, P = 0.01) with marker D2S118 near GDF8 (2q32.2). The present results gave suggestive evidence that the myostatin pathway might be important for strength phenotypes, and GDF8, CDKN1A, and MYOD1 are potential candidate regions for a further and denser mapping with respect to these phenotypes.

Heritability of somatotype components from early adolescence into young adulthood: a multivariate analysis on a longitudinal twin study

BACKGROUND

Several studies with different designs have attempted to estimate the heritability of somatotype components. However they often ignore the covariation between the three components as well as possible sex and age effects. Shared environmental factors are not always controlled for.

AIM

This study explores the pattern of genetic and environmental determination of the variation in Heath-Carter somatotype components from early adolescence into young adulthood.

SUBJECTS AND METHODS

Data from the Leuven Longitudinal Twin Study, a longitudinal sample of Belgian same-aged twins followed from 10 to 18 years (n = 105 pairs, equally divided over five zygosity groups), is entered into a multivariate path analysis. Thus the covariation between the somatotype components is taken into account, gender heterogeneity can be tested, common environmental influences can be distinguished from genetic effects and age effects are controlled for.

RESULTS

Heritability estimates from 10 to 18 years range from 0.21 to 0.88, 0.46 to 0.76 and 0.16 to 0.73 for endomorphy, mesomorphy and ectomorphy in boys. In girls, heritability estimates range from 0.76 to 0.89, 0.36 to 0.57 and 0.57 to 0.76 for the respective somatotype components. Sex differences are significant from 14 years onwards. More than half of the variance in all somatotype components for both sexes at all time points is explained by factors the three components have in common.

CONCLUSIONS

The finding of substantial genetic influence on the variability of somatotype components is further supported. The need to consider somatotype as a whole is stressed as well as the need for sex- and perhaps age-specific analyses. Further multivariate analyses are needed to confirm the present findings.

Markers for cardiovascular disease in monozygotic twins discordant for the use of third-generation oral contraceptives

Oral contraceptives (OC) modulate the risk for developing cardiovascular (CV) diseases. The aim of this study was to determine whether the use of third-generation OC has an impact on markers of CV disease in genetically identical women. We performed an intrapair comparison in 27 monozygotic twin pairs, one of whom was taking third-generation OC, whereas the other was not using OC. Biometric parameters were ascertained and conventional and 24-h ambulatory blood pressure (BP) was recorded. A fasting blood sample was taken for the measurement of glucose, insulin, proinsulin, lipids, and insulin-like growth factor binding protein-1 (IGFBP-1). Insulin resistance and beta-cell function were calculated by homeostasis model assessment (HOMA). A 24-h urine sample for cortisol was obtained. Third-generation OC use increased 24-h ambulatory systolic and diastolic BP by 5.2 and 3.9 mmHg, respectively (both P=0.0003). There was no effect on glucose, insulin and proinsulin levels, and on HOMA parameters, but the IGFBP-1 levels were markedly raised (P=0.0009). The lipid profile showed a 34% increase in triglyceride levels (P < 0.0001), but also a 7% increase in HDL-cholesterol levels (P=0.037). Use of third-generation OC impacts on CV disease markers in young-adult genetically identical women. Some changes are beneficial (increased HDL-cholesterol), whereas others may be deleterious (increased BP and triglyceride levels) or have unknown effects at this time (increased IGFBP-1 levels).

Influence of weight-bearing exercises on bone acquisition in prepubertal monozygotic female twins: a randomized controlled prospective study

The aim of this study was to determine whether high-impact exercises have an osteogenic effect in 21 prepubertal female monozygotic twins aged 8.7 (SD 0.7) years. Bone mineral density (aBMD), bone mineral content (BMC), bone area, and body composition were derived from DXA. Skeletal maturity was assessed by the Tanner-Whitehouse technique. Anthropometric dimensions (28 dimensions) were measured and also used to derive adiposity and muscularity indices, and information about physical activity was obtained by questionnaire. These measurements were taken before and after the exercise period. The exercise program consisted of high-impact exercises. During 9 months, one girl of each twin pair performed the exercises 3 times a week under supervision of a teacher while their sisters served as control group. At baseline there were no differences between the groups. After 9 months, exercisers (Ex) and controls (Con) had similar increases in height and weight. Significant lower adiposity was observed in the exercise group vs the control group. None of the bone indices differed significantly between the two groups. When the analyses were done for a subgroup of twin pairs (n = 12) who did not participate in high-impact sports during their leisure time, significant differences were obtained for aBMD and BMC of the proximal femur in favor of the exercise group. These results indicate that for prepubertal girls who are not involved in sport activities or who are only involved in low-impact sport activities this exercise program has an osteogenic effect on the proximal femur, but for girls who are already involved in high-impact sports this protocol does not have any additional effect on the bone status.

Age at menarche in relation to anthropometric characteristics, competition level and boat category in elite junior rowers

BACKGROUND

Within the context of the effects of training for sports on growth and maturation, there is very little menarcheal data for elite rowing athletes. Knowledge of the relationship of the maturational status with training level, different boat categories, and somatic features of the athletes will clarify the assumed impact of rowing training on the growth and maturational process of youngsters.

AIM

The aim of this study was to determine the age at menarche in world top junior rowing athletes and to investigate its relationship with anthropometric characteristics, and competition level, rowing style and boat category.

SUBJECTS AND METHODS

The sample consisted of 212 female junior rowers, with a mean chronological age of 17.6 +/- 0.8 years, all participants at the 1997 FISA World Junior Rowing Championships. Anthropometric dimensions, somatotype and body composition characteristics were measured, and age at menarche and training data were retrospectively obtained by questionnaires.

RESULTS

Results revealed that the mean age at menarche of the total group of rowers was 12.8 +/- 1.2 years and did not differ from a non-athletic reference population. Rowers who started their rowing training before menarche (n = 78) showed a significant (p </= 0.01) later age at menarche compared with rowers who started their training after menarche (n = 134), with mean ages of 13.4 and 12.4 years, respectively. No significant relationship between the age at menarche and physical and body composition characteristics could be demonstrated, with r varying between -0.11 and 0.11. Furthermore, no significant differences in ages at menarche between competition levels (finalists versus non-finalists/medallists versus non-medallists) and between the different boat categories could be observed.

CONCLUSIONS

Based on the results of this study, there is no direct evidence to state that intensive rowing training has a negative influence on the maturation status of junior female athletes.

Relation between cardiovascular risk factors at adult age, and physical activity during youth and adulthood: the Leuven Longitudinal Study on Lifestyle, Fitness and Health

This study investigated the relationship between sports participation/physical activity during youth (13 - 18 years of age) and adulthood (30 - 40 years of age), and cardiovascular risk factors (body fat and fat distribution, blood pressure, lipoprotein levels and cardiorespiratory fitness) at 40 years of age. Subjects were 166 Flemish males from "The Leuven Longitudinal Study on Lifestyle, Fitness and Health". Physical activity was assessed by means of a sports participation inventory and the Tecumseh community Health Study Questionnaire. In addition to correlation and multiple stepwise regression analyses, different groups (at risk, not at risk) were contrasted on sports participation/physical activity parameters using ANOVA. Long-term exposure during adulthood to daily physical activity was slightly related to a low/high risk profile for waist circumference, percent body fatness, triglycerides and peak VO(2). Sports participation during adolescence was not related to levels of cardiovascular risk factors at 40 years of age.

Body composition estimations by BIA versus anthropometric equations in body builders and other power athletes

BACKGROUND

Two main questions are stated: 1) are BIA and anthropometric equations accurate in estimating body composition in male power athletes and more specifically in body builders and 2) is there a difference in body composition when body builders are compared to weight and power lifters?

METHODS

EXPERIMENTAL DESIGN

this is a descriptive, comparative study on a selected sample of power athletes.

PARTICIPANTS

49 Belgian elite and sub-top male power athletes (34 body builders and 15 weight and power lifters) were included in this sample. More than 70% was in preparation of competition at time of data collection.

MEASURES

an extended set of anthropometric measures was taken. Body composition was estimated by BIA (Bioelectrical Impedance Analysis) and by regression equations of skinfolds. Somatotype and muscle+bone areas were calculated. Factor analysis on all anthropometric measures was carried out to determine the body structure of the athletes.

RESULTS

Compared to external visual criteria, the equations of Durnin and Womersley and Lohman (skinfolds) and the Guo-equation (BIA) were the only equations that could accurately estimate the body composition for this specific group of athletes. However, the sum of skinfolds attains the most accurate estimate of subcutaneous fatness. Body builders have significantly (p<0.01) larger arm and thigh circumferences and are more mesomorfic than the other power athletes (5.9 vs 3.8).

CONCLUSIONS

This study shows that to estimate body composition in extreme power athletes BIA is not as accurate as compared to anthropometric equations. Moreover, the sum of a larger set of skinfolds is preferred to anthropometric prediction equations. In addition, body builders are more muscular and leaner than other power athletes.

Bone mass and lifetime physical activity in Flemish males: a 27-year follow-up study

PURPOSE

The present population study is conducted to examine the extent to which lifetime physical activity and lifestyle parameters contribute to bone mass.

METHODS

The design of the project is a 27-yr prospective follow-up study. Subjects are 126 males gathered from the Leuven Longitudinal Study on Lifestyle, Physical Fitness and Health, and aged 13 yr at the onset of the study and 40 at the end of the follow-up. Physical activity and lifestyle parameters are obtained with questionnaires. Bone mass is measured by means of dual-energy x-ray absorptiometry (DXA).

RESULTS

Results from correlation and regression analyses show that the body mass index (BMI) is the most important parameter in relation to cortical and trabecular bone mass at every examination period. Longitudinally, static arm strength, running speed, and upper muscular endurance contribute significantly to the prediction of adult bone mass. The parameter "change in motor fitness" between 18 and 13 yr old was used to control for hereditary influences. The score for static arm strength and trunk muscle strength demonstrates a significant correlation with adult total bone mineral content (BMC) and lumbar bone mineral density (BMD), respectively. At the age of 40, the Baecke sports index is almost equally important as BMI in explaining the variance in BMD, and static arm strength is the most important parameter (after BMI) for BMC.

CONCLUSION

Lifetime physical activity, physical fitness, and BMI all contribute to adult bone mass. The clinical relevance of these findings is emphasized by the fact that the observed patterns of physical activity and motor fitness pertain to customary lifestyle and are thus feasible targets.

Birth weight and blood pressure in young adults: a prospective twin study

BACKGROUND

The intrauterine environment may be a critical period for the development of hypertension in later life. In the present study, we applied the twin approach to estimate the contribution of genetic and environmental causes that may underlie the birth weight-adult blood pressure association.

METHODS AND RESULTS

Birth weights of 418 twin pairs were obtained prospectively, and resting and 24-hour ambulatory blood pressures were obtained at the age of 18 to 34 years. In women, resting systolic blood pressure decreased 4.27 mm Hg (P<0.001) and diastolic pressure decreased 2.18 mm Hg (P=0.02) per kilogram increase in birth weight. Similar associations were found for ambulatory measurements, although these were somewhat less pronounced. Pair-wise analysis confirmed these findings: twin pairs of whom both members had a low birth weight (<2500 g) had a higher systolic blood pressure compared with twins who both had a high birth weight (>/=2500 g). Systolic blood pressure of the lightest of a low-birth-weight pair was >/=4.7 mm Hg (P=0.02) higher and of the heaviest >/=2.4 mm Hg higher (P=0.2) than similar measurements in high-birth-weight pairs. Intrapair differences in blood pressure between the lightest and the heaviest at birth were only present in low-birth-weight pairs. The results were similar for monozygotic and dizygotic twin pairs. In men, no associations were found between birth weight and adult blood pressure.

CONCLUSIONS

These findings suggest that prenatal programming of adult blood pressure occurs at least in female twins. We suggest that particularly maternal influences, experienced by both twin members, may underlie the association between birth weight and blood pressure. The fetoplacental unit seems to influence blood pressure only when both fetuses had low birth weight.

The influence of zygosity and chorion type on fat distribution in young adult twins consequences for twin studies

An adverse intra-uterine environment has been associated with abdominal fat distribution in singletons. Twins often have a low birth weight and a short gestation. Therefore, they may have an increased risk to develop abdominal obesity. Furthermore, monozygotic monochorionic twins (MZ MC) have a larger intra-pair birth weight difference compared to monozygotic dichorionic twins (MZ DC). If adult anthropometry is programmed in utero, this may affect the intra-pair correlations in adulthood and, consequently, also the results from the classic twin method to estimate genetic and environmental influences. In the present study, we compared the absolute values, the intra-pair differences, and the intra-pair correlations of body mass, height, BMI, and abdominal fat distribution of 424 MZ MC, MZ DC and dizygotic (DZ) twin pairs (aged 18-34 yrs). DZ, MZ DC and MZ MC twins did not differ for most anthropometric characteristics. Only MZ women tended (p = 0.03) to accumulate more abdominal fat compared to DZ twins. Overall, the contribution of zygosity and chorion type to adult anthropometry was rather low (< or = 1.7%). Although the intra-pair birth weight difference of MZ MC pairs (10.5% in men, 12.3% in women) was significantly larger compared to that of MZ DC pairs (6.9% and 9.2% resp.), the intra-pair differences in adult anthropometry were similar for both MZ twin types. Also the intra-pair correlations of MZ MC and MZ DC pairs were strikingly alike, suggesting no significant influence of the prenatal environment on adult concordance. In conclusion, the substantial difference in the prenatal environment of MZ MC and MZ DC twins did not result in a difference in intra-pair concordance of adult anthropometry and fat distribution. Therefore, we suggest that the chorion type of MZ twins does not bias the twin design and the estimation of the genetic contribution to adult anthropometry.

Birth weight and body composition in young adult men--a prospective twin study

OBJECTIVES

To evaluate the association between birth weight and adult body composition in twins, controlling for maternal and genetic influences.

DESIGN

Twins were randomly selected from the East Flanders Prospective Twin Survey, a population-based historic twin cohort.

SUBJECTS

Male members of 229 twin pairs between 18 and 34 y of age who participated in the Prenatal Programming Twin Study.

MEASUREMENTS

Adult body mass, height, BMI, lean body mass, sum of skinfolds and waist-to-hip-ratio. Lean body mass, sum of skinfolds and waist-to-hip-ratio were also adjusted for body mass. Intra-pair difference in adult anthropometric measures between the heaviest and the lightest twin at birth.

RESULTS

Per kg increase in birth weight, body mass (4.2 kg), height (3.3 cm), lean body mass (3.1 kg) and to a lesser extent BMI (0.49 kg/m(2)) increased, whereas waist-to-hip-ratio (-1.4%) and sum of skinfolds (-0.11 s.d.) decreased, when adjusted for body mass. In a pair-wise analysis, the heavier twin at birth was taller and heavier as an adult, but, when adjusted for body mass, he had a lower waist-to-hip-ratio, less subcutaneous fat, and more lean body mass, compared to his lighter sib. Intra-pair difference in body composition was associated with intra-pair birth weight difference in monozygotic and dizygotic twins.

CONCLUSIONS

An adverse intra-uterine environment, as measured by birth weight, is associated with more subcutaneous and abdominal fat and less lean body mass in adulthood. This association is independent of maternal and genetic influences. However, we cannot exclude the existence of genes that act on both birth weight and adult body composition.

Tracking of physical fitness during adolescence: a panel study in boys

PURPOSE

To investigate the tracking in physical fitness (PF) viewed as a whole, a multidimensional trait of the subject, and to establish the stability of each factor of PF in adolescence from the perspective of a panel study using the structural equation modeling approach.

METHODS

From a sample of 454 boys followed from 12 to 18 yr of age of the Leuven Growth Study, we considered only three consecutive measurement occasions with a mean age of 12.76, 14.69, and 17.73 yr. Physical fitness was evaluated by means of a battery composed of the following tests: plate tapping, sit and reach, vertical jump, arm pull, leg lifts, bent arm hang, and shuttle run. Structural equation models were fitted to the data, namely autoregressive models with latent variables. These models were used to quantify the tracking of PF as a whole and also of the individual marker variables of fitness.

RESULTS

Stability estimates of PF as a whole are rather high, beta21 = 0.86 and beta32 = 0.68, with an explained variance of 74% and 73%, respectively. Tracking coefficients represented by disattenuated autocorrelations among the fitness factor gave high results: r1,2 = 0.86; r1,3 = 0.78; and r2,3 = 0.85.

CONCLUSIONS

Physical fitness as a whole is highly stable in adolescent years and very predictable from early years. The same is observed for each factor of fitness. Moreover, autoregressive models within the context of structural equation modeling are better suited than simple Pearson or Spearman autocorrelations to study the tracking problem of PF.

Trends in BMI among Belgian children, adolescents and adults from 1969 to 1996

OBJECTIVE

To document secular data on changes in the distribution of body mass index (BMI), to determine the probability of overweight at 40 y of age in Belgian males in relation to the presence or absence of overweight at different ages in adolescence, and to estimate tracking of BMI in Belgian males in Belgium aged 12-40 y.

DESIGN

Cross-sectional and mixed longitudinal surveys in nationally representative samples of Belgian males and females.

SUBJECTS

Cross-sectional-more than 21 000 boys and 9698 girls; to examine secular trends-3164 boys and 5140 girls; to examine tracking-161 males.

MEASURES

Body mass and height to determine BMI.

RESULTS

In Belgian children the degree of overweight has increased between 1969 and 1993. Tracking of BMI is high in adolescence (r=0.77) and adulthood (r=0.69-0.91) and moderate from adolescence to adulthood (r=0.49). In Belgian males, the probability of overweight at 40 y of age in the presence of overweight at different ages in adolescence is important (odds ratios 5.0-6.9).

CONCLUSIONS

Cross-sectional and longitudinal data, trends and tracking of BMI from 1969 until 1996 in Belgium indicate an increase in the degree of childhood overweight and obesity. Moreover, the risk of an overweight male adolescent becoming an overweight adult is substantial. Measures to restrict the Belgian overweight and obesity epidemic should be taken.

Evaluation of the influence of cardiorespiratory fitness on diverse health risk factors, independent of waist circumference, in 40-year-old Flemish males

OBJECTIVE

To examine whether cardiorespiratory fitness is associated with health risk factors, independent of abdominal obesity (waist circumference).

RESEARCH METHODS AND PROCEDURES

Data from 141 40-year-old Flemish male subjects were used in a cross-sectional design. The main outcome measure in this study was the health risk profile, composed of lipid parameters, blood pressure, and body composition parameters. Data were analyzed by regression analysis and by means of analysis of covariance with waist circumference (WC) as covariate and cardiorespiratory fitness as source of variance.

RESULTS

The data demonstrated that cardiorespiratory fitness was significantly associated with triglycerides, with the ratio of total cholesterol/serum high density lipoprotein cholesterol, and with percent body fat, independent of an association with WC.

DISCUSSION

Major findings of the present cross-sectional study indicate that a high WC is associated with adverse health-related lipid profile and body composition characteristics and that relatively high levels of aerobic fitness attenuate the health risk associated with a large WC.

Genetic variance of adolescent growth in stature

The aim of this study is to quantify the genetic and environmental variation in biological parameters of the adolescent growth in stature in both sexes, using structural equation models. Standing height was measured in 99 twin pairs from the Leuven Longitudinal Twin Study. Subjects were seen at semi-annual intervals between 10 and 16 years and at 18 years. Preece-Baines model I was fitted to the individual data and biologically meaningful parameters were derived. Path models were fitted to these parameters and a gender heterogeneity analysis was performed. A model including additive genetic and specific environmental factors (AE-model), allowing for a difference in total variance or in genetic/environmental variance components in males and females best explains most of the growth characteristics. For the timing and velocity of the adolescent growth spurt, no gender heterogeneity was observed, and the genetic (0.89 to 0.93) and specific environmental (0.07 to 0.11) contributions were equal in both sexes. For stature at take-off, stature at peak height velocity and for adult stature, gender heterogeneity was observed and different models appeared to result in the best fit for boys and girls. For height at PHV and adult stature, the significant contribution of a common environmental (0.39 to 0.56) factor in boys was noteworthy. For percentage of adult stature and distances between relevant time points of the growth curve, a non-scalar effect was observed, indicating that different genes affect these characteristics in boys and girls. It is concluded that most characteristics of the growth spurt in stature are under strong genetic control. Gender heterogeneity is present for stature and for a number of derived growth characteristics.

The contribution of anthropometric characteristics to performance scores in elite female gymnasts

BACKGROUND

Aims of this study were: a) to identify anthropometric variables correlated with gymnastic performance, and b) to predict performance scores from a combination of anthropometric dimensions.

METHODS

EXPERIMENTAL DESIGN

correlational analysis and a stepwise multiple regression were used.

SETTING

Subjects were participants at the 24th World Championships Artistic Gymnastics, Rotterdam, The Netherlands, in 1987.

PARTICIPANTS

A total of 168 female gymnasts (mean age: 16.5 +/- 1.8 years) were investigated. Each gymnast participated in all events.

MEASURES

An extensive battery of anthropometric dimensions was taken on each athlete. The somatotype was estimated. Skeletal maturation of the hand-wrist was assessed. Competition scores for the four individual gymnastic events (balance beam, floor exercise, vault, uneven bars) and a composite score for each gymnast were the dependent variables.

RESULTS

Moderately high, significant correlations (p < 0.01) were observed between skinfolds and endomorphy, and gymnastics performance scores, r varying from -0.38 to -0.60, for biceps skinfold and the score on balance beam, and for endomorphy and the total score, respectively. The correlations suggest that gymnasts with more subcutaneous fat and higher endomorphy have lower performance scores. About 32% to 45% of the variance in gymnastic performance scores could be explained by anthropometric dimensions and/or derived variables, but endomorphy and chronological age are the most important predictors.

CONCLUSIONS

There is a relatively strong relationship between several anthropometric variables and gymnastic performance in a sample of elite female gymnasts, but the associations are not sufficiently high to predict performance scores on an individual basis.

Associations between physical activity, nutritional practices and health-related anthropometry in Flemish males: a 5-year follow-up study

OBJECTIVE

To examine the extent to which extent health-related anthropometric characteristics such as body mass index, waist-hip ratio, waist girth, percentage of body fat and weight gain are associated with physical activity and nutritional habits in a prospective follow-up study.

DESIGN

A 5-y prospective follow-up study.

SUBJECTS

132 healthy men from The Leuven Longitudinal Study on Lifestyle, Physical Fitness, and Health.

MEASUREMENTS

The main outcome measures in this study were body mass index, waist-hip ratio, waist girth, percentage of body fat and significant weight gain at the ages of 35 and 40y. An unhealthy body composition was defined as a body mass index above 26, a waist-hip ratio above 0.95, a waist girth and body fat percentage above percentile 75 at the end of the 5-y follow-up period and a significant weight gain of 5 kg or more between the two examination periods. Anthropometric characteristics were derived from clinical examination. Physical activity at the age of 35 and 40 and nutritional habits at the age of 40 were determined from questionnaires.

RESULTS

Physical activity was the most important predictor for the waist-hip ratio in this sample. In contrast, nutritional habits show a stronger relationship with body mass index. The absolute amount of energy intake is not as important as the dietary factors in predicting subjects with overweight or an unhealthy body composition. The index of occupational activities appears to be the most important physical activity variable.

CONCLUSION

The relative contribution of physical activity and nutritional habits in health-related anthropometry varies with the characteristic considered. It is important to include all components of physical activity, and occupational activities in particular, in determining these relationships in a general population sample.

Acquired microcephaly after low Apgar score in Zimbabwe

Serial head circumference measurements were made on 165 African babies born with a 5 min Apgar score of 5 or less. Measurements were taken at birth and at 4, 9, and 12 months of age. In the majority of infants the onset of microcephaly could be diagnosed as early as 4 months of age. Twenty-five of the 142 infants were microcephalic at 1 year. Neurological development was impaired in 19 of the 25 (76 per cent) microcephalic infants and in 18 of the 117 (15 per cent) normocephalic infants. Fourteen of the 16 (88 per cent) infants with severe quadriplegia developed microcephaly before the age of 4 months. A decreased rate of head growth during the first 4 months of life in African infants born with a low Apgar score correlates closely with the development of microcephaly. Infants with an acquired microcephaly have a high probability of developing neurologic impairment by the age of 1 year. Serial head circumference measurement in low Apgar score babies in developing countries is an easy, simple, and inexpensive method to detect microcephaly.

Ulnar variance and skeletal maturity of radius and ulna in female gymnasts

It is has been suggested that repetitive loading on the distal end of the radius in elite gymnasts may lead to epiphyseal changes, a premature closure (union) of the radius growth plate, and ulnar overgrowth.

PURPOSE

It is hypothesized that ulnar overgrowth in female gymnasts is associated with advanced maturity status and early onset of epiphyseal closure of the radius, and later maturity status and later onset of epiphyseal closure of the ulnar.

METHODS

Posterior-anterior radiographs of 201 female gymnasts, participants of the 1987 World Championships Artistic Gymnastics, were used to measure ulnar overgrowth, to determine skeletal maturation of the hand and wrist with the Tanner-Whitehouse technique, and to determine the maturity status of the radius and ulna separately, particularly with regard to the onset of epiphyseal closure. To test the hypothesis, extreme quintiles for ulnar overgrowth were contrasted for skeletal maturation of the hand and wrist and for maturity stages of the radius and ulna as defined by the Tanner-Whitehouse criteria.

RESULTS

Female gymnasts who demonstrate ulnar overgrowth are skeletally more advanced in maturity status of the entire hand-wrist compared with gymnasts who did not show ulnar overgrowth. There were, however, no differences between gymnasts in the extreme quintiles of ulnar overgrowth in the maturation of the radius, although gymnasts with ulnar overgrowth show more advanced maturity status of the ulna.

CONCLUSIONS

Ulnar overgrowth is thus not apparently associated with advanced maturity of the distal radial epiphysis as defined in protocols for assessing skeletal maturity and does not apparently lead to premature epiphyseal closure of the distal radius.

Genetic determinants of sports participation and daily physical activity

OBJECTIVE

The purpose is to review the existing literature on genetic determinants of sports participation, daily physical activity (PA) resting metabolic rate (RMR) and activity as a temperamental trait.

DESIGN

A synthesis will be given of the published material on this topic with special focus on twin and family data, and association and linkage studies.

MEASUREMENTS

Self reported sports participation, daily PA, RMR and activity as a temperamental trait.

ANALYSIS

Transmission and heritability coefficients calculated from twin and family data will be reported.

RESULTS

The reported heritability coefficients for sports participation vary between 0.35-0.83, and those for daily PA between 0.29-0.62. If one of the parents or co-twins is active in sports, it is more likely that the child or co-twin is also active in sports (odds ratios (ORs) vary from 1.2-5.8). Twin and parent-child correlations for RMR also indicate a moderate genetic effect. At present, only a linkage between RMR and uncoupling protein 2 markers has been demonstrated.

CONCLUSION

The genetic determination of sports participation, daily PA and RMR, varies from low to moderately high, and only between the uncoupling protein 2 genetic marker and RMR has a linkage has been demonstrated.

Neurodevelopmental outcome at 1 year in Zimbabwean neonates with extreme hyperbilirubinaemia

The study concentrates on estimating the magnitude of the effect of a single risk factor, maximum total serum bilirubin (TSB) in excess of 400 micromol/l (23.4 mg/dl), on the neurodevelopmental outcome of 50, singleton, Zimbabwean neonates at 1 year of age. At 1 year corrected age the Bayley Scales of Infant Development (BSID) was administered. Two infants died and five were lost to follow up. TSB was neither associated with birth weight nor with gestational age. Of 43 infants with a TSB > 400 micromol/l (23.4 mg/dl),11(26%) scored abnormal on the BSID at 1 year of age and 5 (12%) infants developed the choreoathetoid type of cerebral palsy.

CONCLUSION

Infants with bilirubin levels between 400 and 500 micromol/l (23.4 and 29.2 mg/dl) who scored abnormal or suspect on the Bayley Scales of Infant Development were preterm or had haemolytic disease. All term infants without haemolysis and with bilirubin levels between 400 and 500 micromol/l (23.4 mg/dl-29.2 mg/dl) were normal at 1 year of age.

Univariate and multivariate genetic analysis of subcutaneous fatness and fat distribution in early adolescence

Univariate and multivariate analyses of the genetic and environmental contributions to variance in adipose tissue and adipose tissue distribution were carried out in early adolescents. Stature, weight, body mass index (BMI), and five subcutaneous skinfolds were measured at half-yearly intervals in 105 MZ and DZ twin pairs from 10 to 14 years. The most parsimonious model, which provided an adequate explanation for variation in the BMI, five skinfolds, and the T/E ratio, included additive genetic and specific environmental factors. Multivariate analyses of the genetic architecture of subcutaneous fat indicated a general skinfold genetic factor, an extremity skinfold genetic factor, and skinfold specific genetic factors. This implies that all skinfolds are under control of the same set of genes, that a different set of genes partly controls extremity skinfolds, and that other genes have a small skinfold specific impact. Environmental contributions included a general skinfold environmental factor and skinfold specific environmental factors. BMI is under control of the same set of genes as skinfolds and shows high genetic correlations with trunk skinfolds, which implies that nearly the same genes may influence trunk skinfolds and the BMI. All models were fairly consistent across the age range.

Neurological status in severely jaundiced Zimbabwean neonates

Neurological status was studied in 50 jaundiced infants with a total serum bilirubin of > 400 mumol/l (23.4 mg/dl). Infants were assessed in the neonatal period with the Neonatal Neurological Examination and 4 months of age with the Infant Motor Screen. Twenty-six (52 per cent) infants were premature. Analysis of variance did not show a significant difference between gestational age, birth weight, and maximum total serum bilirubin or between gestational age, birth weight, and neurological optimality score. Based on the presence of abnormal neurological syndromes the infants were classified as normal (n = 27), suspect (n = 11), or abnormal (n = 12). Serum bilirubin levels were higher (p < 0.0001) and the neonatal neurological examination scores lower (p < 0.0001) in the seven (14 per cent) infants who received an exchange transfusion. In the transfused group four out of seven infants and in the non-transfused group seven out of 43 infants were classified as abnormal (p < 0.03). The Neonatal Neurological Examination was shown to be sensitive in detecting neurodevelopmental abnormalities in the neonatal period, with a sensitivity of 83 per cent, specificity of 88 per cent, positive predictive value of 62 per cent, and negative predictive value of 96 per cent.

The predictive value of developmental testing of extremely jaundiced African infants

The predictive value of the Neonatal Neurological Examination (NNE) adapted from Prechtl (1977) and the Infant Motor Screen (IMS) from Nickel (1989) at 4 months was studied in severely jaundiced infants in Zimbabwe. Fifty infants were examined with the NNE, 41 with the IMS and 43 with the Bayley Scales of Infant Development (BSID) (Bayley 1969). Five infants had choreoathetosis and six had a motor delay at age 1 year. The NNE and IMS proved to be sensitive instruments particularly when two infants who became malnourished after the neonatal period were excluded. Logistic regression was used to investigate the relation between the BSID and five selected predictors from the NNE. This resulted in a correct classification of 93%. By using only the predictors acoustic blink and traction response, 80% of the infants were correctly classified but the number of false negatives was reduced from three to one.

Neonatal neurological examination as a predictor of neuromotor outcome at 4 months in term low-Apgar-score babies in Zimbabwe

The predictive value of the neonatal neurological examination (NNE) adapted from Prechtl, was investigated in 139 term Zimbabwean infants born with an Apgar score of five or less at 5 min. At 4 months, seven infants had died and 13 were lost to follow-up, leaving 119 infants to undergo the Infant Motor Screen (IMS). Eighty-eight infants were diagnosed as normal, six as suspect and 25 as abnormal at screening. The sensitivity, specificity, positive predictive value and negative predictive value of the NNE were 94%, 55%, 42% and 96%, respectively. Seventeen (14%) infants had developed microcephaly at 4 months and 13 (77%) of them scored abnormal on the IMS. Twenty-three of the 48 (48%) infants who had convulsions within 48 h of birth, were diagnosed as abnormal (P < 0.0001). The NNE proved to be very sensitive in detecting neurodevelopmental abnormalities in the neonatal period and the five abnormal syndromes derived from the NNE were able to correctly identify 94% of the abnormal infants.

Neurodevelopmental outcome in babies with a low Apgar score from Zimbabwe

The early identification of neurological dysfunction in the neonatal period, the predictive value of single items of the neonatal neurological examination (NNE) adapted from Prechtl and the developmental outcome at 1 year of age in infants with a low Apgar score in Zimbabwe were studied. One hundred and sixty-five infants were examined with the NNE and 142 with the Bayley Scale of Infant Development (BSID) at 1 year of age. Twenty-three infants had cerebral palsy, ten had a motor delay or developmental delay, and four were mentally retarded. The NNE proved to be a sensitive instrument for detecting neurodevelopmental abnormality. Logistic regression analysis was used to investigate the relationship between the BSID and nine selected predictors from the NNE. This resulted in a correct classification of 94%. However, the number of false negatives was high. By using only the variability of movements and fixation as predictors the number of false negatives was reduced to one.

Extreme hyperbilirubinaemia in Zimbabwean neonates: neurodevelopmental outcome at 4 months

As part of a prospective study of severely jaundiced Zimbabwean infants, the relationship between maximum total serum bilirubin (TSB) concentration in the neonatal period and neurodevelopmental outcome at the corrected age of 4 months was studied. Fifty infants with a TSB of > 400 micromol/l (23.4 mg/dl) were enrolled and screened with a neonatal neurological examination (NNE). The cause of jaundice was low birth weight in 22 (44%), ABO incompatability in 8 (16%), sepsis in 8 (16%) and congenital syphilis (6%) in 3 infants. In 9 infants a cause could not be determined. At 4 months, 2 infants had died and 3 were lost to follow up, leaving 45 infants for the infant motor screen (IMS) at 4 months of age. Mean TSB in the neonatal period was 485 micromol/l (28.2 mg/dl), and 7 infants received an exchange transfusion. Mean TSB of the infants with an exchange transfusion was 637 micromol/l (37.2 mg/dl) (range 429-865 micromol/l (25-50.3 mg/dl)) and of the infants without transfusion 459 micromol/l (26.8 mg/dl) (range 400 740 micromol/l (23.4-43 mg/dl)) (P < 0.0001). The TSB was not associated with birth weight, gestational age, gender or head circumference of the baby. On the IMS, 6 of 45 (13.3%) infants scored abnormal, 6 (13.3%) suspect and 33 (73%) scored normal. Three of the six (50%) remaining infants who received an exchange transfusion scored abnormal on the IMS while only 3 of the 39 (8%) infants without exchange transfusion were abnormal.

CONCLUSION

More than 25% of infants with a TSB of > 400 micromol/l (23.4 mg/dl) scored abnormal or suspect at 4 months of age and half of these infants already showed irreversible neurological symptoms. All infants who scored abnormal or suspect on the IMS with bilirubin levels between 400 and 500 micromol/l (23.4 and 29.2 mg/dl) had haemolytic disease or were premature.

Development and tracking in fitness components: Leuven longtudinal study on lifestyle, fitness and health

In the Leuven Growth Study of Belgian Boys the growth and physical performance of Belgian boys followed longitudinally between 12 and 19 years were studied. Subsequently, a subsample (n = 240) of Flemish-speaking males were reexamined at 30 and 35 years. A first question relates to the individual growth patterns in a variety of physical fitness characteristics. The three strength tests (static, functional, explosive) show curves that are qualitatively similar to those for height and weight. Their adolescent spurts occur after the height spurt. Flexibility and the two speed tests appear to reach maximum velocities prior to the height and weight spurts. Longitudinal principal component analysis was applied to the study of growth patterns of several somatic and motor characteristics. The results for height show three components sufficient to provide an adequate representation of the original information. The first component characterizes the general position of an individual growth curve. Components 2 and 3 reflect fluctuation in percentile level during the age period studied and can be conceived as indices of stability and are related to age at peak height velocity (APHV) and peak height velocity (PHV), respectively. Relationships between somatic characteristics, physical performance, and APHV have been studied in a sample of 173 Flemish boys, measured yearly between +/- 13 and +/- 18 years and again as adults at 30 years of age. The sample was divided into three contrasting maturity categories based on the APHV. There are consistent differences among boys of contrasting maturity status during adolescence in body weight, skeletal lengths and breadths, circumferences, and skinfolds on the trunk. There are no differences in skinfolds on the extremities. None of the differences in somatic dimensions and ratios among the three contrasting maturity groups are significant at 30 years of age except those for subscapular skinfold and the trunk/extremity skinfold ratio. During adolescence, speed of limb movement, explosive strength and static strength are negatively related to APHV; thus, early maturers performed better than late maturers. However, between late adolescence and adulthood (30 years), the late maturers not only caught up to the early maturers, but there were significant differences for explosive strength and functional strength in favor of late maturers. Finally, age-specific tracking, using inter-age correlations, of adult health- and performance-related fitness scores were investigated. In addition, the independent contribution of adolescent physical characteristics to the explanation of adult fitness scores was also studied. Tracking between age 13 and age 30 years was moderately high (46% of variance explained) for flexibility, low to moderate (between 19% and 27% of variance explained) for the other fitness parameters and low for pulse recovery and static strength (7% to 11% of variance explained). Between age 18 and age 30 years the tracking was high for flexibility, moderately high for explosive and static strength, and moderate for the other fitness parameters except for pulse recovery. The amount of variance of adult fitness levels explained increased significantly when other characteristics observed during adolescence entered the regressions or discriminant functions.

Prospective and retrospective longitudinal studies of the growth, maturation, and fitness of Polish youth active in sport

Results of three longitudinal studies of the growth, maturation and fitness of youth active in sport are summarized. Data include size attained and growth rates for height and body mass, secondary sex characteristics, skeletal age, age at peak height velocity, and two indicators of fitness, peak O2 uptake and power output at a heart rate of 170 bpm (PWC 170). The data for active youth are compared to local reference data and where appropriate to data from other European longitudinal studies. Allowing for variation in methodology and sampling, regular training in sport during puberty and the adolescent spurt does not influence size attained, growth rate, and the timing and progression of somatic, sexual and skeletal maturation in boys and girls. Active and nonactive boys and girls, respectively, do not differ significantly in the mean age at maximum growth in power output at a heart rate of 170 bpm. Boys active in sport, however, have a greater maximal gain in submaximal power output than nonactive boys. Analysis of ontogenetic allometry of peak oxygen uptake and stature and body mass indicate variation between individuals, and between boys of contrasting maturity status.

Neurological findings in neonates with low Apgar in Zimbabwe

OBJECTIVES

Document neurological condition of African neonates with a low apgar score.

SETTING

Mpilo Hospital, Bulawayo, Zimbabwe.

SUBJECTS

165 babies with an Apgar score of 5 or less at 5 min.

METHODS

Neurological examination at term age according to Prechtl. Babies were classified as normal, suspect or abnormal and compared with two reference groups, one from Groningen, the Netherlands and one from Grenada in the Caribbean.

RESULTS

A higher number of Zimbabwean babies were delivered by Caesarean section compared to the Groningen group (P < 0.001). Babies delivered by vacuum extraction scored significantly lower compared to babies delivered by Caesarean section (P < 0.003). Twenty abnormal signs derived from the neonatal neurological examination proved to be predictive on the total optimality score (P < 0.001). The number of infants who were classified as abnormal was higher in the Zimbabwean population (P < 0.01).

CONCLUSION

The selected abnormal signs derived from the neonatal neurological examination proved to be highly predictive on the neurological condition. The neonatal morbidity in Zimbabwean neonates with a low Apgar score was higher when compared with two reference groups from Groningen and Grenada.

Gender-specific regional changes in genetic structure of muscularity in early adolescence

Genetic and environmental influences on muscle circumference measurements of the extremities were estimated in 105 pairs of twins between 10 and 14 yr of age. Four circumferences, extended upper arm (EAC), forearm (FC), thigh (TC), and calf (CC), were measured. Univariate model fitting revealed that the largest part (87-95%) of the variance for all circumferences at most ages was explained by additive genetic factors. Sex differences were observed for some age categories. Multivariate analyses showed a different pattern evolving according to age and gender. In boys from 10 to 12 yr of age, one general genetic factor influenced all four circumferences. With increasing age, an arm-leg model emerged, one genetic factor influencing the arm and another genetic factor the leg circumferences. In young girls one genetic factor loaded on the proximal (EAC, TC) and another on the distal (FC, CC) circumferences. With subjects at age 14 yr, an arm-leg model was observed. High genetic correlations indicated that genetic factors related to EAC, FC, TC, and CC did not act independently. The age-and gender-specific changes in the genetic structure suggest pubertal influences. This study shows that muscle circumferences are highly heritable characteristics and are therefore a promising starting point at which to locate their genes. Gene mapping could validate the gender-specific change of the genetic structure with age and region.

Maturity-associated variation in peak oxygen uptake in active adolescent boys and girls

Maturity-associated variation in peak O2 uptake was considered in a longitudinal sample of 47 boys and 40 girls who were enrolled in sports schools. The children were followed annually from 11 to 14 years of age. O2 uptake and heart rate were measured during a maximal exercise test on a cycle ergometer. For boys, individual velocity curves were used to operationally define maturity groups: early-decreasing velocities from 11 to 14 years, n = 9; average-velocities reaching a peak and then decreasing, n = 7; and late-increasing velocities from 11 to 14 years, n = 31. The distributions of stages of genital and public hair development were consistent with early, average and late maturity status designation based on velocities of stature growth. Prospectively collected ages at menarche were used to define maturity groups in girls: early--< 12.0 years, n = 7, 10.8 +/- 0.6 years; average--12.0.12.9 years, n = 20, 12.4 +/- 0.3 years; and late-- > or = 13.0 years, n = 13, 13.5 +/- 0.4 years. Early maturing boys had a greater O2 uptake at each observation period. Early and average maturing girls did not differ in maximal O2 uptake, but both had greater O2 uptake than late maturers. When expressed per unit body mass, differences among the three maturity groups of boys were reduced and not significant. Late maturing girls tended to have greater maximal O2 uptake per unit body mass than early and average maturing girls, but the differences were not significant at all ages. However, with body mass at the first observation as the covariate in analyses of covariance, the three maturity groups of boys differed significantly in peak VO2 at each observation, while the three maturity groups of girls did not. Thus, removing the confounding effect of body mass on O2 uptake by simply dividing the measured values by mass is of limited utility.

Birth weight and its relationship to size attained and relative fat distribution at 7 to 12 years of age

The relationship between birth weight and relative subcutaneous fat distribution at school age was considered in 131 boys and 106 girls 7 to 12 years of age. Relative fat distribution at school age was estimated with the ratio of the subscapular to triceps skinfolds (S/T) for the total sample, and with the ratio of the sum of two trunk (subscapular, midaxillary) to the sum of two extremity (triceps, medial calf) skinfolds (T/E) for subsamples of 102 boys and 63 girls. There were no sex differences in the S/T ratio (mm/mm), boys 0.62 +/- 0.15, girls 0.63 +/- 0.18; T/E ratio (mm/mm), boys 0.58 +/- 0.13, girls 0.59 +/- 0.16; and BMI (kg/m2), boys 17.1 +/- 2.4, girls 16.9 +/- 2.2. Second order partial correlations, controlling for age and the BMI or age and sum of skinfolds, between birth weight and the skinfold ratios are, respectively, -0.22 and -0.20 (p < 0.01) for S/T and -0.29 and -0.32 (p < 0.01) for T/E in girls, and -0.18 and -0.17 (p < 0.05) for S/T and -0.06 and -0.6 for T/E in boys. Though low, the correlations suggest that as birth weight decreases proportionally more subcutaneous fat is accumulated on the trunk than on the extremities, more so in females than in males. Results of stepwise multiple regression analyses indicate that birth weight accounts for from 2% to 8% of the variance in relative subcutaneous fat distribution at school age.

Anthropometric and motor characteristics of Senegalese children with different nutritional histories

The effects of Protein Energy Malnutrition (PEM) on the motor performance of 4.5-6.5-year-old Senegalese children were studied. Body dimensions included weight, lengths, circumferences, and four skinfolds. Motor performance tests included a 3-min endurance run, 4 x 10 m shuttle-run, distance throw, standing long jump and grip strength. The sample consisted of 147 children: 52 children who were hospitalized for severe undernutrition (severe UN group) during infancy but who had been nutritionally rehabilitated; 63 children who were never severely malnourished but who were chronically exposed to mild-to-moderate undernutrition up to the time of study (chronic UN group); and 32 well nourished children (well nourished group) from well-off households. After adjusting for sex and age, the well nourished group performed better than the severe UN and chronic UN groups. Principal components analysis resulted in two factors which explained 65% of the variance in anthropometry and motor performance. One was related to body size and the second to body composition. The three nutritional groups differed significantly in principal component scores for the two factors; chronic UN and severe UN children also differed for the second factor. Body composition, especially low fat mass appeared to be an important feature for motor performance in chronically undernourished children.

Physique as a risk factor for ulnar variance in elite female gymnasts

The aims of this study were: 1) to determine ulnar variance variability of elite, female gymnasts; 2) to evaluate the relationship between ulnar variance and physique, maturity status, and training characteristics of these gymnasts. All 156 skeletally immature female gymnasts were participants at the World Championships Artistic Gymnastics, Rotterdam, The Netherlands, in 1987. Chronological ages varied between 13.1 and 20.6 yr (mean = 15.9 +/- 1.3 yr). A large set of anthropometric dimensions was taken and somatotype was determined by the Heath-Carter technique. Skeletal age was assessed by the Tanner-Whitehouse II method. Menarcheal status and training data were collected by questionnaire. Ulnar variance was determined according to Hafner et al. Gymnasts differ significantly from reference girls with respect to physique and maturational status: gymnasts were smaller and delayed in skeletal maturity with about 1.5 yr. For those who had attained menarche, mean age at menarche was 15.1 +/- 1.3 yr. Ulnar variance shows a normal distribution in the gymnasts, ranging from -10.5 mm to +5.9 mm, which is somewhat more positive, i.e., an ulnar overgrowth, than reference wrists. The relationship between ulnar variance and somatic and maturational features suggests that female gymnasts who are more mature and have a physique characterized as relatively tall with a high lean body mass are at greater risk for developing a positive ulnar variance. No relationship between ulnar variance and training characteristics was evident. It is concluded that the observed positive ulnar variance in this sample of elite female gymnasts is less pronounced than originally stated in most "case reports."

Gymnast wrist: an epidemiologic survey of ulnar variance and stress changes of the radial physis in elite female gymnasts

The ulnar variance in female gymnasts attending the World Championship Artistic Gymnastics Rotterdam 1987 was measured. There was a marked increase in the ulnar length in adult as well as immature gymnast compared with nonathletes. The changes in relative ulnar length were correlated to weight, height, and skeletal age of the athletes. In 10% of the gymnasts' wrists we noted so-called "stress-related changes" of the distal physis of the radius. Repetitive injury and compression of the wrist leads to a premature closure of the distal radial growth plate resulting in secondary ulnar overgrowth.

Size, fatness and relative fat distribution of males of contrasting maturity status during adolescence and as adults

The somatic characteristics of boys of contrasting biological maturity status during adolescence are compared from 13-18 years and at 30 years of age. Within the mixed longitudinal Leuven Growth Study of Belgian Boys, 173 boys were followed annually from 13-18 years and were subsequently measured at 30 years of age. Age at peak height velocity (PHV) was estimated for 149 boys and the sample was then divided into three contrasting maturity categories based on the age at PHV: early (PHV < 13.37 years), average (PHV between 13.85 and 14.80 years) and late (PHV > 15.27 years) maturers. Using ANOVA for repeated measures and one-way ANOVA, differences in 18 somatic dimensions and five ratios of body proportions and subcutaneous fat distribution among the three maturity groups were tested from 13-18 years and at 30 years of age. There are consistent differences among boys of contrasting breadths, circumferences,and skinfolds on the trunk. There are no differences in skinfolds on the extremities. None of the differences in somatic dimensions and ratios among the three contrasting maturity groups are significant at 30 years of age except those for subscapular skinfold and the trunk/extremity skinfold ratio. Thus, during adolescence and in adulthood, late maturing boys have a distribution of subcutaneous fat that is associated with lower risk for several adult degenerative diseases.

Cardiovascular reactivity in isometric exercise and mental arithmetic in children

In children, we studied noninvasively the cardiovascular stress responses, including changes over time of systolic blood pressure (SBP), heart rate (HR), and stroke volume (SV) in isometric handgrip (IHG) and mental arithmetic. Specifically, we asked whether 1) these cardiovascular stress responses were different for the two stress conditions in children, 2) these responses differed in boys and girls, and 3) the anthropometric variables related to these stress responses. SV differed significantly between IHG and mental arithmetic over the entire stress period. This may reflect higher systemic vascular resistance during IHG. HR in boys was lower than in girls over the entire period of stress in both stress tests. This observation cannot be attributed to differences in conditioning, because this should not influence responses to isometric or mental stress. A larger left ventricular mass was related to higher SVs. A marked relationship was found between HR and SBP and between HR and SV. No relationship was found between SBP and SV.