How to assess physical activity? How to assess physical fitness?

Regular aerobic physical activity (PA) increases exercise capacity and physical fitness (PF), which can lead to many health benefits. Accurate quantification of PA and PF becomes essential in terms of health outcome and effectiveness of intervention programmes. In this manuscript we present a review regarding the assessment of physical activity and fitness. Three types of PA assessment methods can be distinguished: criterion methods, objective methods and subjective methods. Criterion methods like doubly labelled water, indirect calorimetry and direct observation are the most reliable and valid measurements against which all other PA assessments methods should be validated, but they also hold important drawbacks. Objective PA assessment methods include activity monitors (pedometers and accelerometers) and heart rate monitoring. Finally, questionnaires and activity diaries are considered subjective methods. For the assessment of PF, we distinguish field tests and laboratory tests. The Eurofit for Adults is a test battery that is designed to assess health-related fitness of individuals, communities, sub-populations and populations. It is mainly used for evaluating the morphological component, the muscular component, the motor component and the cardio-respiratory component. In the laboratory, exercise capacity is preferentially assessed through maximal incremental exercise testing. Cardio-pulmonary exercise testing is a well-established procedure that provides a wealth of clinically diagnostic and prognostic information. The peak oxygen uptake is the gold standard in the assessment of exercise tolerance. When maximal exercise is contraindicated or not achievable, the VAT or the submaximal slopes provide reasonable alternatives.

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.

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.

Muscular Strength, Aerobic Fitness, and Metabolic Syndrome Risk in Flemish Adults

PURPOSE

To investigate the association of muscular strength and aerobic fitness with a continuous metabolic syndrome risk score in male and female adults.

METHODS

This cross-sectional study included 1019 (571 men) Flemish adults, aged 18-75. Muscular strength was evaluated by measuring isometric knee extension and flexion peak torque, using a Biodex System Pro 3 dynamometer. Aerobic fitness was quantified as VO2peak and was determined during a maximal cycle ergometer exercise test. Both strength and aerobic fitness were scaled for differences in FFM, using allometric analyses. A validated metabolic syndrome risk score that was based on waist circumference, triglycerides, blood pressure, fasting plasma glucose, and HDL cholesterol was used. Metabolic syndrome risk score, strength, and aerobic fitness were analyzed as continuous variables using multiple linear regression.

RESULTS

Metabolic syndrome risk was inversely associated with strength, independently of aerobic fitness, and after adjustment for age, height, education level, smoking status, and dietary intake in women (beta = -0.172, P < 0.001). In men, however, adjustment for aerobic fitness attenuated the inverse association between strength and metabolic syndrome risk (beta = -0.044, P > 0.05). Independently of strength, aerobic fitness was inversely associated with metabolic syndrome risk (men: beta = -0.309, P < 0.001; women: beta = -0.208, P < 0.001). Furthermore, independent associations were found for strength and aerobic fitness with several individual metabolic syndrome risk factors in women, and most of these associations were only partially mediated by central and general adiposity indicators.

CONCLUSION

Although cross-sectional, the present results support inclusion of strength training in addition to aerobic exercise in physical activity recommendations for women, because both types of activity might show additional effects in reducing the risk of the metabolic syndrome.

Genetic factors in physical activity levels: a twin study

BACKGROUND

Substantial interindividual variation is observed in sports participation and physical activity levels in youth. This study aimed to (1) estimate the relative contribution of genes, along with shared and nonshared environmental factors, to variation in sports participation index (SPI) and leisure-time physical activity (LTPA); and (2) test differences in those factors in males and females.

METHODS

The sample was comprised of 411 Portuguese twin pairs of different zygosity aged 12 to 25 years. The SPI and LTPA were assessed with the Baecke questionnaire. Quantitative genetic modeling was used to test alternative models for the presence of additive gene effects (a(2)), common or shared environment within the family (c(2)), and unique environmental factors (e(2)).

RESULTS

The best-fitting models showed sex-specific effects for the two phenotypes. Variance components for SPI in males were a(2)=68.4%, c(2)=20%, and e(2)=11.6%; and in females, a(2)=39.8%, c(2)=28.4%, and e(2)=31.8%. For variation in LTPA, genetic factors in males explained 63%, common environment was not significant, and unique environment explained 37%. In females, contributing factors were a(2)=32%, c(2)=38%, and e(2)=30%.

CONCLUSIONS

Genetic effects explained a considerable amount of variation in SPI and LTPA, which were greater in males than in females. The relevance of shared environmental factors (family and peers) and nonshared environmental factors in SPI and LTPA is particularly evident in females.

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.

Birth weight and body composition in young women: a prospective twin study

BACKGROUND

The intrauterine environment may be critical for the development of obesity. Alternatively, the same genetic factors may influence both birth weight and adult body composition.

OBJECTIVE

We evaluated the association between birth weight and adult body composition in female twins, which allowed us to control for maternal and genetic influences.

DESIGN

Of 447 twin pairs randomly selected from the East Flanders Prospective Twin Survey, 238 pairs, aged 18-34 y, participated. Adult body mass, height, and lean body mass were measured, and the body mass index (BMI), waist-to-hip ratio, and sum of skinfold thicknesses were calculated. The twins were considered as individuals and pairs.

RESULTS

When the twins were considered as individuals, twins who were heavier at birth were taller (3.3 cm/kg greater birth weight) and slightly heavier (1.13 kg/kg greater birth weight) as adults than were lighter twins. They also had more lean body mass and less subcutaneous and abdominal fat at birth. Pairwise comparison showed that for every level of intrapair birth weight difference (> or = 5%, > or = 10%, and > or = 15%), the twin who was heavier at birth was taller in adult life (0.8, 1.2, and 2.0 cm, respectively). When the intrapair birth weight difference exceeded 15%, the heavier twin was also heavier (3.1 +/- 6.08 kg) as an adult than her much lighter sister.

CONCLUSION

Birth weight accounts for some of the differences in adult body composition between twins.

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.

Anthropometric indicators of nutritional status: implications for fitness, activity, and health in school-age children and adolescents from Maputo, Mozambique

BACKGROUND

Studies are needed to test the relevance of the anthropometric criteria for health and well-being, particularly in developing countries.

OBJECTIVE

The objective of the study was to identify the relevance of anthropometric indexes as indicators of nutritional status.

DESIGN

The sample consisted of 2316 subjects (n = 1094 males, 1222 females) aged 6-18 y from Mozambique. Anthropometric variables, maturity stage, physical fitness, physical activity, and metabolic fitness were measured. Samples of blood, urine, and feces were obtained. Subjects were classified in 5 nutritional groups labeled normal, low height-for-age (stunted), low weight-for-height (wasted), low height-for-age and low weight-for-height (stunted and wasted), and overweight, according to cutoffs set by a World Health Organization expert committee. Socioeconomic status was classified according to region of residence.

RESULTS

Prevalence rates for males and females, respectively, in the nutritional groups were 3.0% and 2.3% (stunted group), 21.9% and 10.0% (wasted group), 3.0% and 0.8% (stunted and wasted group), and 4.8% and 7.7% (overweight group). With control for age, socioeconomic status, and maturity stage, the overweight group performed significantly worse than did the other groups on most of the fitness tests. Compared with the normal group, the 3 undernourished groups performed significantly worse in absolute strength tasks, better in endurance tasks, and equally in flexibility and agility. Very few differences were found in physical activity scores. The 3 undernourished groups had scores for the biochemical indicators that were similar to those of the normal group and had more favorable profiles for blood pressure and cholesterol.

CONCLUSIONS

In this population, the cutoffs used to classify overweight status appear to appropriately identify potential health problems. No relevance to health was found for the lower cutoffs identifying undernourished children.

Motor performance during adolescence and age thirty as related to age at peak height velocity

Relationships between motor performance, as measured by various fitness tests, and age at peak height velocity 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. In addition to correlation studies, comparisons were made between boys with an early, average and late age at peak height velocity. To summarize the successive measurements during adolescence, a longitudinal principal component analysis was carried out. The first component can be interpreted as an average percentile level component. During adolescence, three performance tasks, namely speed of limb movement, explosive strength and static strength, are negatively related to age at peak height velocity; thus early maturers performed significantly better than late maturers. However, between late adolescence and adulthood, a cross-over of the average distance curves between 18 and 30 years of age was noted for almost all motor tasks. The late maturers not only caught up the early maturers, but there were significant differences for explosive strength and functional strength in favour of late maturers. In order to predict performance in adulthood from measures during adolescence, the following hypothesis is suggested: the best results at adulthood are obtained by those men who were already good performers during adolescence and who were late maturers, while the worst results are obtained by poor performers during adolescence who were early maturers.

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.

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.

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.

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.

Tracking of physical fitness and physical activity from youth to adulthood in females

PURPOSE

To evaluate stability of physical fitness and physical activity from adolescence into middle adulthood in Flemish females.

METHODS

Within the scope of the Leuven Longitudinal Study on Lifestyle, Fitness and Health, 138 females (mean age=16.6+/-1.1 yr) from the Leuven Growth Study of Flemish Girls were seen in adulthood (mean age=40.5+/-1.1 yr). Several body dimensions and motor fitness tests were taken. Physical activity was assessed by means of a sports participation inventory. Inter-age correlations were calculated between adolescent and adult values. Cross-tabulation was used to identify the percentage of subjects remaining in the same BMI and physical activity group or shifting from one group to another from adolescence to adulthood. Odds ratios for less activity and overweight in adulthood according to adolescent activity or weight status were calculated.

RESULTS

Except for flamingo balance, plate tapping, leg lifts, and arm pull, all anthropometric and physical fitness characteristics were stable from adolescence to adulthood (r ranging from 0.49 to 0.96). Sports participation was not a stable characteristic (r=0.13). From adolescence to adulthood, 84.5 and 63.6%, respectively, remained in the normal-weight and overweight group, whereas 62.5 and 54.4%, respectively, remained in the less active and active group. The odds of being overweight in adulthood was 9.53 (95% CI: 3.1-29.8) times greater in overweight compared with normal-weight adolescent girls.

CONCLUSION

In Flemish females, anthropometric and fitness characteristics demonstrate higher levels of stability from adolescence to middle adulthood than physical activity. Weight status during adolescence is indicative of adult weight status, and a pattern of less activity rather than activity tends to continue from youth to adulthood.

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.

Secular trends in anthropometric characteristics, physical fitness, physical activity, and biological maturation in Flemish adolescents between 1969 and 2005

In this study, secular trends in anthropometric characteristics, physical fitness, physical activity, and biological maturity over the past 25-35 years in Flemish adolescents were investigated. Representative cross-sectional samples of 12-18-year-old secondary school children (11,899 assessments in boys in 1969-1974, 4,899 girls in 1979-1980, 1,429 boys and 1,772 girls in 2005) and parent-offspring pairs tested at approximately the same age during adolescence (55 father-son pairs, mean age fathers = 15.47 years, mean age sons = 15.38 years; 62 mother-daughter pairs, mean age mothers = 16.63 years, mean age daughters = 15.01 years) were used. The cross-sectional data were analyzed in 6 yearly age-categories using Wilcoxon rank sum tests. For the parent-offspring data paired t-tests, simple linear regressions to adjust for parent-offspring differences in chronological age and multiple linear regressions to adjust for parent-offspring differences in chronological and skeletal age were conducted. The cross-sectional study generally revealed an increase in weight, stature, BMI, skinfolds and trunk-extremity index, and a decrease in the performance on several physical fitness tests. In the parent-offspring study, only sons were maturationally advanced compared to fathers. Even after adjustment for parent-offspring differences in chronological age and in chronological and skeletal age, results for stature, trunk-extremity index and physical fitness were generally similar to the cross-sectional study. No secular trend was observed for sports participation. The fact that the positive secular trends in weight, BMI, and skinfolds of the cross-sectional study were not entirely confirmed in the parent-offspring study is probably due to higher similarity in genetic and familial background, higher socio-economic status, and more health-consciousness of the latter.

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.

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.

Socio-economic status, growth, physical activity and fitness: The Madeira Growth Study

BACKGROUND

Within a country social conditions change over time and these conditions vary from country to country. The associations between these conditions, somatic growth, physical activity and fitness reflect these changes.

AIM

The study documented variation in somatic growth, physical activity and fitness associated with socio-economic status (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. Anthropometric measurements included lengths, body mass, skeletal breadths, girths and skinfolds. Physical activity and SES were collected via questionnaire and interview. Physical fitness was assessed using the Eurofit test battery. Variation in somatic growth, physical activity and physical fitness by SES (high, average and low) was tested with analysis of variance.

RESULTS

Significant differences between SES groups were observed for height, body mass and skinfolds. Boys and girls from high SES groups were taller, heavier and fatter (subscapular and triceps skinfolds) than their peers from average and low SES groups. At some age intervals, the high SES group had larger skeletal breadths (girls) and girths (boys and girls) than low SES. Small SES differences were observed for physical activity (sport and leisure-time indices). SES was significantly associated with physical fitness. At some age levels, boys from the low SES group performed better for muscular and aerobic endurance whereas girls from the high SES group performed better for power.

CONCLUSION

Considerable variation in somatic growth and physical fitness in association with SES has been demonstrated, but little association was found for physical activity.

Skeletal maturity in Belgian youths assessed by the Tanner-Whitehouse method (TW2)

Reference data for skeletal maturity (TW2 method) of the hand and wrist are provided for large representative samples of Belgian boys and girls. The sample of Belgian boys consisted of 21,174 boys aged 12 to 20 years studied in a nationwide cross-sectional and longitudinal study on the physical fitness of secondary schoolboys (1969-1974). The girls' sample consisted of 9698 6-19-year-old Flemish girls studied cross-sectionally (1979-1980). Both samples were multi-stage stratified cluster samples of entire school classes. All skeletal maturity assessments of the boys were made by the same observer (GB). His estimations agreed quite closely with those of the originators of the method. The skeletal age assessments of the girls were made by two observers trained by GB. Both observers showed high intraobserver reliability after training, and during the assessments. Moreover their ratings compared favourably with those of GB and the originators of the method. Smoothed percentile curves of the maturity scores (TW2-20 bone, RUS and CARP scores) were calculated by means of cubic splines using a stepwise regression procedure for the selection of suitable knots. In the boys, the TW2 scores (20 bone and RUS) increase linearly between 12 and 14.5 years of age, slow down for a while, and then increase again, while the CARP scores increase linearly between 12 and 15 years of age. In girls, the 20-bone maturity scores increase nearly linearly from 6 through 9.5 years of age, accelerate until 11.0 years followed by a smaller increase; RUS scores increase curvilinearly from 6 years of age onwards; and Carp scores increase almost linearly between 6.0 and 12.5 years of age. Belgian boys are advanced in RUS scores but are delayed for the carpal bones as compared with the British standards. The Belgian girls show advancement for both scales as compared with the British reference data. The skeletal maturation of youths from several other continental European countries corresponds more closely with the Belgian than with the British data. The reference data presented herein most probably provide suitable standards for youths of West-European countries.

Anthropometric characteristics of outstanding male and female gymnasts

Anthropometric data of outstanding gymnasts were gathered on the occasion of the 24th World Championship Artistic Gymnastics, held at Rotterdam, The Netherlands, in October 1987. In total 165 males and 201 females were investigated, constituting 84% of the total number of participants. The data of these gymnasts were descriptively compared with both reference data and data reported in previous studies on gymnasts competing at international events. Also, based on the data obtained, 'gymnastic-specific' anthropometric reference values (i.e. profile charts), were established for both male and female gymnasts. Finally, the maturational characteristics (skeletal age and menarche) of the 'Rotterdam' female gymnasts were described.

Daily physical activity and physical fitness from adolescence to adulthood: A longitudinal study

The stability of physical fitness and physical activity in Flemish males from 18 to 40 years of age was investigated. In addition, effects of a consistently low-activity or high-activity level during the same age period on physical fitness were studied. The sample consisted of males who were followed longitudinally from age 13 to age 18 years, and were remeasured at the ages of 30, 35, and 40 years. Complete data about physical fitness and physical activity between 13 and 40 years were available for 130 subjects. Stability was measured using Pearson autocorrelations and simplex models. Multivariate analysis of variance (MANOVA) for repeated measurements was used to look for the effects of activity level on physical fitness. Simplex models showed higher stability coefficients than Pearson correlations, and stability of physical fitness was higher than stability of physical activity. Physical fitness showed the highest stability in flexibility (r = 0.91 between 18 and 30 years, r = 0.96 for both the 30-35 and 35-40 ages intervals), while physical activity showed the highest stability during work (r between 0.70 and 0.98 for the 5-year intervals). Results from MANOVA indicated that for some fitness characteristics the high-active subjects were more fit than their low-active peers. Stability of physical activity was higher than assumed and, therefore, it is a useful and independent indicator for further research. Although possible confounding factors are present (e.g., heredity), a higher level of physical activity during work and leisure time on a regular basis benefits physical fitness considerably. Am. J. Hum. Biol. 12:487-497, 2000. Copyright 2000 Wiley-Liss, Inc.