Maternal inactivity: 45-year trends in mothers' use of time

OBJECTIVE

To examine 45-year trends in time use and physical activity energy expenditure (PAEE) in a nationally representative sample of US mothers.

PARTICIPANTS AND METHODS

We quantified time allocation to physical activity (PA), sedentary behaviors (SED), and PAEE from 1965 to 2010 in mothers with older children (MOC) (>5 to ≤18 years) and mothers with younger children (MYC) (≤5 years). Physical activity was the sum of time allocated to housework, child care, laundry, food preparation, postmeal cleanup, and exercise. Sedentary behavior was the sum of time spent in a vehicle and using screen-based media. Physical activity energy expenditure was calculated using body weights from national surveys and metabolic equivalents.

RESULTS

From 1965 to 2010, the time allocated to PA decreased by 11.1 h/wk (from 32.0 to 20.9 h/wk) in MOC and by 13.9 h/wk (from 43.6 to 29.7 h/wk) in MYC. The time spent in SED increased by 7.0 h/wk in MOC (from 17.7 to 24.7 h/wk) and increased by 5.7 h/wk in MYC (from 17.0 to 22.7 h/wk). Physical activity energy expenditure decreased by 1237.6 kcal/wk (176.8 kcal/d) in MOC (from 5835.3 to 4597.7 kcal/wk), and in MYC, PAEE decreased by 1572.5 kcal/wk (224.6 kcal/d), from 7690.5 to 6118.0 kcal/wk.

CONCLUSION

There was a significant reallocation of time by mothers from PA (eg, housework) to SED (eg, watching television) between 1965 and 2010. Given the essential role of PA for health and the potential for the intergenerational transmission of obesity and obesogenic behaviors, these results suggest that maternal inactivity may be an important target for the primary prevention of chronic noncommunicable diseases and obesity.

Validation of maturity offset in a longitudinal sample of Polish boys

Abstract This study attempted to validate an anthropometric equation for predicting age at peak height velocity (APHV) in 193 Polish boys followed longitudinally 8-18 years (1961-1972). Actual APHV was derived with Preece-Baines Model 1. Predicted APHV was estimated at each observation using chronological age (CA), stature, mass, sitting height and estimated leg length. Mean predicted APHV increased from 8 to 18 years. Actual APHV was underestimated at younger ages and overestimated at older ages. Mean differences between predicted and actual APHV were reasonably stable between 13 and 15 years. Predicted APHV underestimated actual APHV 3 years before, was almost identical with actual age 2 years before, and then overestimated actual age through 3 years after PHV. Predicted APHV did not differ among boys of contrasting maturity status 8-11 years, but diverged among groups 12-15 years. In conclusion, predicted APHV is influenced by CA and by early and late timing of actual PHV. Predicted APHV has applicability among average maturing boys 12-16 years in contrast to late and early maturing boys. Dependence upon age and individual differences in actual APHV limits utility of predicted APHV in research with male youth athletes and in talent programmes.

Validation and factorial invariance of children's attraction to physical activity (CAPA) scale in Portugal

The Children's Attraction to Physical Activity (CAPA) scale assesses interest in and attraction to the physical activity (PA) of children of elementary school age. The original (25 items) and shorter versions (15 items) of the scale were developed and validated with American children. The purpose of this study was to cross-validate the shorter version of the CAPA scale for use with Portuguese schoolchildren and to examine the invariance of the multidimensional factor structure of the scale in two samples. The sample comprised 683 children (7-10 years) from public primary schools. The sample was divided into calibration and cross-validation samples. The scale was translated into Portuguese and underwent forward translation, synthesis of the translation and backward translation and was then subjected to expert committee review, pretest and reliability assessment. Internal consistency for each of the five subscales within the a priori 5-factor structure of the CAPA scale was evaluated through Cronbach's alpha, followed by a series of confirmatory factor analyses (CFAs) for both the calibration and cross-validation samples. The maximum likelihood robust estimation method was used. The CFA demonstrated that a 5-factor structural model of the Portuguese translation of the CAPA scale was invariant. The construct analysed had the same basic meaning and structural and item differences within the two samples. The results indicated that the CAPA scale is appropriate for use with Portuguese schoolchildren. The availability of a valid and reliable scale should enhance opportunities for further understanding of children's involvement in PA.

Altitude effects on growth of indigenous children in Oaxaca, Southern Mexico

The effect of altitude of residence on the growth status of 11,454 indigenous school children 6-14 years of age in Oaxaca, southern Mexico, was examined. Indicators of living conditions (human development index [HDI], index of community nutritional risk [INR], index of marginalization [IM], index of relative isolation [II]) were regressed on z-scores for height, weight and BMI, and the residuals were regressed on altitude of residence (km). Independent of other environmental conditions, altitude negatively affected height by approximately -0.07 z-scores per kilometer altitude above sea level. The estimated average decrease in stature was 0.92 cm per kilometer elevation. BMI was significantly increased, 1.2 units per kilometer elevation, consistent with earlier studies of growth status and altitude. In contrast, weight was not affected by altitude of residence. Approximately 36% of the reduction in height and 54% of the increase in BMI were due to altitude effects; the remaining changes in height and BMI were associated with environmental factors reflected in the indices of community well-being considered.

Ventricular mass in relation to body size, composition, and skeletal age in adolescent athletes

OBJECTIVE

To examine the contribution of chronological age (CA), skeletal age (SA), stature, sitting stature, fat-free mass (FFM), and fat mass (FM) to interindividual variability in left ventricular mass (LVM) in male adolescent roller hockey players using allometric models.

DESIGN

Cross sectional.

SETTING

Training and competitive sport during adolescence.

PARTICIPANTS

Seventy-three Portuguese male roller hockey players aged 14.5 to 16.5 years.

INDEPENDENT VARIABLES

Stature, sitting stature, body mass, estimated FM and FFM, and SA assessed by the Fels method.

MAIN OUTCOME MEASURES

Allometric modeling of LVM assessed in accordance with recommendations of the American Society of Echocardiography.

RESULTS

Hockey players (CA: 15.4 ± 0.6 years; SA: 16.4 ± 1.5 years) showed an eccentric remodeling of LV structure within the reference range (ie, 0.24-0.42), a dilated LV chamber, but no LVM increase. Exponents for body size descriptors were 2.69 for stature (R(2) = 27%; P < 0.001), 2.49 for sitting stature (R(2) = 37%; P < 0.001), 0.76 for FFM (R(2) = 31%; P < 0.001), and 0.22 for FM (R(2) = 26%; P < 0.001). The combination of size descriptors with CA and SA increased the explained variance in LVM slightly (26%-45%).

CONCLUSIONS

When stature and FM are used for indexing LVM in a sample of adolescent athletes, biological maturity status should also be considered.

Changes in the genetic variance and heritability of the body mass index and skinfolds among Polish twins aged 8-18 years

Body Mass Index (BMI) and skinfolds are common indicators of adiposity. Many studies have shown relationships between the BMI in childhood and adolescence and the BMI in adulthood. Similar correlations were observed for the skinfolds, although they tend to be lower. The aim of this study was to estimate changes with age in the genetic variance and heritability of the BMI and skinfolds among Polish twins born between 1959 and 1965. Observations involved male and female monozygotic (MZ) and dizygotic (DZ) twins, who were measured annually between 8 and 18 years of age. Body Mass Index and skinfold thicknesses at the triceps (TSF), subscapular (SSF) and suprailiac (SIF) sites were measured. Genetic variance and heritability were estimated for individual skinfold thicknesses, the sum of three skinfolds (SUMSF) and BM, separately by age classes for both sexes. Intraclass correlations were significantly higher for MZ twins than for DZ twins in both sexes and across all ages. Heritability estimates were significant for all indicators of adiposity, but varied with age and had different ranges for boys and girls. Estimates of genetic variance were significant for all indicators of adiposity and were higher for girls than for boys.

Nutritional status, biological maturation and cardiorespiratory fitness in Azorean youth aged 11-15 years

BACKGROUND

Sex and individual differences in biological maturity status can influence height, weight, and body fat. Thus, the rigorous control of these variables seems necessary for estimating overweight and obesity in adolescents. The aims of this study were to estimate the prevalence of overweight and obesity and over-fatness in Azorean adolescents and to examine the contributions of chronological age, sex, estimated maturity status, and cardiorespiratory fitness (CRF) to the risk of overweight and obesity and over-fatness.

METHODS

The sample comprised 1,206 youth aged 11-15 years (626 boys and 580 girls) from the Azores Islands, Portugal. Body mass, stature, and skinfolds (triceps and subscapular) were measured. Body mass index (BMI) was calculated and percent fat was predicted from skinfolds. Age- and sex-specific IOTF cut-off values of the BMI defined nutritional status. Biological maturation was estimated as present height expressed as a percentage of predicted adult (mature) stature. The CRF was analyzed from the 20-m shuttle run test.

RESULTS

The total prevalence rates of overweight/obesity and over-fatness were of 31% and 27%, respectively. Low CRF (unfit) and being average and advanced in maturity status were positively and significantly associated with overweight/obesity and with risk of being over-fatness in both sexes.

CONCLUSIONS

High prevalence rates of overweight/obesity and over-fatness were identified in Azorean youth, and low CRF and advanced biological maturation were positively associated with overweight/obesity and over-fatness in our sample of adolescents.

Maturity-associated variation in total and depot-specific body fat in children and adolescents

OBJECTIVES

This study considered the association between sexual maturation and adiposity in children and adolescents, and examined the contribution of sexual maturation to ethnic differences in total and depot-specific body fat.

METHODS

The sample included 382 White and African American 5-18-year-olds. Body mass index (BMI), waist circumference (WC) and sexual maturity status (breast/genital and pubic hair stage) were assessed in a clinical setting. Total body fat (TBF) was measured by dual-energy X-ray absorptiometry and abdominal subcutaneous (SAT) and visceral adipose tissue (VAT) were measured by magnetic resonance imaging. Analysis of covariance adjusted for age was used to examine the association between sexual maturity status and adiposity, and linear regression adjusted for age was used to examine the influence of sexual maturation on ethnic differences in adiposity. Analysis of VAT also controlled for TBF. Significance was accepted at P < 0.05.

RESULTS

Breast/genital stage was significantly associated with BMI, WC, TBF, and SAT in girls of both ethnic groups and in White boys. Breast stage was associated with VAT. Stage of pubic hair was significantly associated with TBF and VAT in White girls only. In girls, sexual maturation attenuated the ethnic effects on BMI and WC, but the ethnic effect in VAT persisted. In boys, sexual maturation did not attenuate ethnic differences on VAT and did not predict WC or SAT. Sexual maturity status independently explained variance in adiposity in girls only.

CONCLUSIONS

Sexual maturity status is an important determinant of pediatric adiposity and attenuates ethnic differences in girls' adiposity.

Allometric scaling of peak oxygen uptake in male roller hockey players under 17 years old

Peak oxygen uptake (V̇O2peak) is routinely expressed in litres per minute and by unit of body mass (mL·kg−1·min−1) despite the theoretical and statistical limitations of using ratios. Allometric modeling is an effective approach for partitioning body-size effects in a performance variable. The current study examined the relationships among chronological age (CA), skeletal age (SA), total body and appendicular size descriptors, and V̇O2peakin male adolescent roller hockey players. Seventy-three Portuguese, highly trained male athletes (CA, 15.4 ± 0.6 years; SA, 16.4 ± 1.5 years; stature, 169.9 ± 6.9 cm; body mass, 63.7 ± 10.7 kg; thigh volume, 4.8 ± 1.0 L) performed an incremental maximal test on a motorized treadmill. Exponents for body size descriptors were 2.15 for stature (R2= 0.30, p < 0.01) and 0.55 for thigh volume (R2= 0.46, p < 0.01). The combination of stature or thigh volume and CA or SA, and CA2or SA2, increased the explained variance in V̇O2peak(R2ranged from 0.30 to 0.55). The findings of the allometric model combining more than 1 body size descriptor (i.e., stature and thigh volume) in addition to SA and CA2were not significant. Results suggest that thigh volume and SA are the main contributors to interindividual variability in aerobic fitness.

Injuries in Portuguese youth soccer players during training and match play

CONTEXT

Epidemiologic information on the incidence of youth soccer injuries in southern Europe is limited.

OBJECTIVE

To compare the incidence, type, location, and severity of injuries sustained by male subelite youth soccer players over the 2008-2009 season.

DESIGN

Descriptive epidemiology study.

SETTING

Twenty-eight Portuguese male youth soccer teams.

PATIENTS OR OTHER PARTICIPANTS

A total of 674 youth male subelite soccer players in 4 age groups: 179 U-13 (age range, 11-12 years), 169 U-15 (age range, 13-14 years), 165 U-17 (age range, 15-16 years), and 161 U-19 (age range, 17-18 years).

MAIN OUTCOME MEASURE(S)

Injuries that led to participation time missed from training and match play prospectively reported by medical or coaching staff of the clubs.

RESULTS

In total, 199 injuries reported in 191 players accounted for 14.6 ± 13.0 days of absence from practice. The incidence was 1.2 injuries per 1000 hours of exposure to soccer (95% confidence interval [CI] = 0.8, 1.6), with a 4.2-fold higher incidence during match play (4.7 injuries per 1000 hours of exposure; 95% CI = 3.0, 6.5) than during training (0.9 injuries per 1000 hours of exposure; 95% CI = 0.6, 1.3) (F₁,₆₇₃ = 17.592, P < .001). The overall incidence of injury did not increase with age (F₁,₆₇₃ = 1.299,P = .30), and the incidence of injury during matches (F₁,₆₇₃ = 2.037, P = .14) and training (F₁,₆₇₃ = 0.927, P = .44) did not differ among age groups. Collisions accounted for 57% (n = 113) of all injuries, but participation time missed due to traumatic injury did not differ among age groups (F₃,₁₁₀ = 1.044, P = .38). Most injuries (86%, n = 172) involved the lower extremity. The thigh was the most affected region (30%, n = 60) in all age groups. Muscle strains were the most common injuries among the U-19 (34%, n = 26), U-17 (30%, n = 17), and U-15 (34%, n = 14) age groups, whereas contusions and tendon injuries were the most common injuries in U-13 players (both 32%, n = 8). The relative risk of injury slightly increased with the age of the competitors.

CONCLUSIONS

The higher incidence of injury during matches than training highlights the need for education and prevention programs in youth soccer. These programs should focus on coach education aimed at improving skills, techniques, and fair play during competitions with the goal of reducing injuries.

Psychosocial correlates of physical activity in school children aged 8-10 years

BACKGROUND

Understanding correlates of physical activity (PA) among children in different populations may contribute to fostering active lifestyles. This study considered gender differences in relationships between biologic (body mass index, BMI), demographic (socioeconomic sport status, SES) and psychosocial correlates of PA and level of PA in Portuguese primary school children.

METHODS

683 children, aged 8-10 years, from 20 different elementary schools in northern Portugal were surveyed. Weight status was classified using International Obesity Task Force (IOTF) criteria for the BMI. Family SES was estimated from school records. PA level and psychosocial correlates (attraction to PA, perceived physical competence and parental socialization) were obtained with interview and standardized questionnaires, respectively. Sex-specific hierarchical multiple regression analyses (SPSS 18.0) were conducted and included two blocks of predictor variables (biologic and demographic, and psychosocial).

RESULTS

Level of PA was significantly higher in boys than girls. Enjoyment of participation in vigorous PA was positively associated with level of PA. Perceived acceptance by peers in games and sports and parental encouragement were positively and significantly related to PA in girls. Perceived physical competence was positively and significantly related to PA in boys. Weight status and SES were not associated with PA.

CONCLUSIONS

Boys and girls differed in perceived attractiveness of PA and perceived physical competence, both of which influenced level of PA. Differences in perceptions may be important aspects of motivation for PA in school children.

Urban-rural contrasts in fitness, physical activity, and sedentary behaviour in adolescents

Research considering physical activity (PA), physical inactivity and health outcomes among urban and rural youth has produced equivocal findings. This study examined PA, physical inactivity, sedentary behaviours and cardiorespiratory fitness (CRF) in adolescents from urban and rural communities in the Portuguese Midlands. The sample included 362 adolescents (165 males, 197 females) of 13-16 years of age. CRF was assessed by the PACER test. A GT1M accelerometer was used to record 5 consecutive days of PA and time spent sedentary. Analyses of covariance (chronological age as co-variate) were performed to test the effect of the area of residence on sedentary behaviour, PA and CRF. Urban youth of both sexes spent less time in sedentary activities than rural youth. Urban males were more active than rural peers at the weekend, whereas urban females were significantly less active than rural females on week days and across all days assessed. Rural youth of both sexes had higher levels of CRF than urban youth. Area of residence was related to aerobic fitness, PA and time spent in sedentary behaviours among Portuguese youth. Interventions seeking to enhance health and active lifestyles in Portuguese youth should consider the potential impact of socio-geographic factors.

Anthropometric characteristics, physical fitness and technical performance of under-19 soccer players by competitive level and field position

Anthropometric characteristics, physical fitness and technical skills of under-19 (U19) soccer players were compared by competitive level (elite, n=95; non-elite, n=85) and playing position (goalkeeper, central defender, fullback, midfield, forward). Fitness tests included 5- and 30-m sprints, agility, squat jump (SJ) and countermovement jump (CMJ), strength and Yo-Yo intermittent endurance test level 2 (Yo-Yo IE2). Soccer-specific skills included ball control and dribbling. Independent of position, elite players presented more hours of training per year than non-elite players (d>1.2). Stature and body mass discriminated elite from non-elite players among goalkeepers and central defenders (d>0.6). Major differences were noted between elite and non-elite goalkeepers for SJ, CMJ, Yo-Yo IE2, and ball control (d>1.2). Elite central defenders performed better than their non-elite counterparts in SJ and ball control tests (d>1.2). Elite players presented better agility and Yo-Yo IE2 performances than non-elite players within all positional roles (d>0.6). In conclusion, U19 players differed in anthropometric characteristics, physical fitness and technical skills by competitive level within field positions.

Adiposity in children and adolescents: correlates and clinical consequences of fat stored in specific body depots

The 2011 Pennington Biomedical Research Center's Scientific Symposium focused on adiposity in children and adolescents. The symposium was attended by 15 speakers and other invited experts. The specific objectives of the symposium were to (i) integrate the latest published and unpublished findings on the laboratory and clinical assessment of depot-specific adiposity in children and adolescents, (ii) understand the variation in depot-specific adiposity and related health outcomes associated with age, sex, maturation, ethnicity and other factors and (iii) identify opportunities for incorporating new markers of abdominal obesity into clinical practice guidelines for obesity in children and adolescents. This symposium provided an overview of important new advances in the field and identified directions for future research. The long-term goal of the symposium is to aid in the early identification of children and adolescents who are at increased health risk because of obesity and obesity-related conditions.

Utility of Childhood BMI in the Prediction of Adulthood Disease: Comparison of National and International References

OBJECTIVE

To determine whether the U.S. Centers for Disease Control and Prevention (CDC; CDC Reference) or International Obesity Task Force (IOTF; IOTF Reference) BMI cut-off points for classifying adiposity status in children are more effective at predicting future health risk.

RESEARCH METHODS AND PROCEDURES

The sample (N=1709) included 4- to 15-year-old (at baseline) boys and girls from the Bogalusa Heart Study. Overweight and obesity status were determined using both the CDC Reference and IOTF Reference BMI cut-off points at baseline. The ability of childhood overweight and obesity, determined from the two BMI classification systems, to predict obesity and metabolic disorders in young adulthood (after a 13- to 24-year follow-up) was then compared.

RESULTS

Independently of the classification system employed to determine adiposity based on childhood BMI, the odds of being obese and having all of the metabolic disorders in young adulthood were significantly (p<0.05) higher in the overweight and obese groups by comparison with the nonoverweight groups. Childhood overweight and obesity, determined by both the CDC Reference and IOTF Reference, had a low sensitivity and a high specificity for predicting obesity and metabolic disorders in young adulthood. Overweight and obesity as determined by the CDC Reference were slightly more sensitive and slightly less specific than the corresponding values based on the IOTF Reference.

DISCUSSION

Overweight and obesity during childhood, as determined by both the CDC and IOTF BMI cut-off points, are strong predictors of obesity and coronary heart disease risk factors in young adulthood. The differences in the predictive capacity of the CDC Reference and IOTF Reference are, however, minimal.

Longitudinal study of repeated sprint performance in youth soccer players of contrasting skeletal maturity status

The purpose of the study was to evaluate the developmental changes in performance in a repeated-sprint ability (RSA) test in young soccer players of contrasting maturity status. A total of 83 regional level Portuguese youth soccer players, aged 11-13 years at baseline was assessed annually. Stature, body mass, 7x34.2-m sprint protocol (25-s active recovery), 20-m multi-stage continuous shuttle endurance run and counter-movement jump (CMJ) without the use of the arms were measured. Fat-free mass (FFM) was determined by age and gender-specific formulas. Developmental changes in total sprint time across ages were predicted using multilevel modeling. Corresponding measurements were performed on an independent cross-sectional subsample of 52 youth soccer players 11-17 years to evaluate the predictive model. CA, CA(2), maturational status (SA-CA), body size (mass and stature), FFM, aerobic endurance, lower limb explosive strength and annual volume training significantly improved the statistical fit of the RSA multilevel model. In 'late' maturing athletes, the best model for predicting change in RSA was expressed by the following equation: 86.54 - 2.87 x CA + 0.05 x CA(2) - 0.25 x FFM + 0.15 x body mass + 0.05 x stature - 0.05 x aerobic endurance - 0.09 x lower limb explosive strength - 0.01 x annual volume training. The best fitting models for players who were 'on time' and 'early' maturing were identical to the best model for late maturing players, less 0.64 seconds and 1.74 seconds, respectively. Multilevel modeling provided performance curves that permitted the prediction of individual RSA performance across adolescent years in regional level soccer players. Key pointsRepeated-sprint ability tests are a valuable sport-specific field test of sprint performance in youth soccer players. Here, the test had reasonable reliability and can be useful to trainers and coaches in the assessment of young athletes and in monitoring changes over time.The total sprint time of youth soccer players advanced in biological maturation improves more, on average, than that of players who are on time (average) and late in maturation. The performance difference between early and late maturing players is consistent after about 13 years of age.Multilevel modeling is a promising statistical technique for analyzing the development of functional capacity in a sport. It has the potential to provide useful information to assist trainers and coaches in evaluating and facilitating the development of individual players.

Prevalence of traditional and novel markers of cardiovascular disease risk in Scottish adolescents: socioeconomic effects

Information on the health status and physical activity of Scottish adolescents is limited. This study examines the prevalence of cardiovascular disease (CVD) risk in Scottish adolescents by socioeconomic status (SES). Participants were recruited from two high schools that differed in the SES of the students in attendance. The sample included 73 boys and 34 girls (16.4 ± 0.6 years). Variables included anthropometry, physical activity, physical fitness, blood pressure, diet, and 11 metabolic markers of CVD risk. Significant sex differences (P ≤ 0.01) were noted for stature, waist circumference, waist-hip ratio, physical activity, cardiorespiratory fitness, muscular power, sprint speed, and several CVD risk factors: high-density lipoprotein (HDL), low-density lipoprotein (LDL), interleukin-6 (IL-6), and C-reactive protein (CRP) levels. Boys from a lower SES had significantly higher levels of glucose and plasminogen activator inhibitor-1 (PAI-1) but lower levels of adiponectin compared with boys from a higher SES. Girls from a lower SES had significantly (P ≤ 0.01) higher glucose and PAI-1 levels but lower levels of insulin and adiponectin than girls from a higher SES. High fat diets, low physical activity levels, and elevated CRP and total cholesterol levels were the CVD risk factors most commonly identified as being at-risk levels in this cohort, regardless of sex or SES. SES differences were not consistently apparent, but several CVD risk factors were identified as elevated in this sample of adolescents, regardless of sex or SES.

Agreement between anthropometric and dual-energy X-ray absorptiometry assessments of lower-limb volumes and composition estimates in youth-club rugby athletes

The purpose of this study was to assess the agreement of lower-limb volume estimates based on anthropometry and dual-energy X-ray absorptiometry (DXA) as a reference method in male rugby athletes. Predictive models using body mass and skinfolds were tested to improve the relative agreement between protocols (anthropometry, DXA). Rugby players (n = 41; 19.9 ± 2.2 years) volunteered for the study. Lower-limb total and fat-free volumes were estimated by anthropometry and also derived using DXA. Cross-validation between the anthropometry technique and DXA was then performed. Lower-limb volume estimates by anthropometry overestimated reference values and tended to be further from the reference values with the increase of scale. For the total sample, standard errors of measurement for volume estimates by anthropometry were 1.99 L and 1.34 L for total and fat-free volumes, respectively. Correlations with reference values were 0.81 for lower-limb volume and 0.90 for lower-limb fat-free volume. Correlations between estimated prediction equations and reference values showed higher correlations (r = 0.96 for lower-limb volume and r = 0.93 for lower-limb fat-free volume) compared with anthropometric estimates. Overall, the agreement of anthropometry method to quantify lower-limb volumes with DXA as a reference in young adult rugby players is acceptable and is a practical method when more expensive and complex techniques are not available. The consideration of body mass and lower-limb skinfolds increases the precision of lower-limb volume estimates using anthropometry in the young adult rugby players.

Cardiorespiratory fitness, weight status and objectively measured sedentary behaviour and physical activity in rural and urban Portuguese adolescents

Relationships among weight status (body mass index [BMI]), cardiorespiratory fitness (CRF) and objective measures of sedentary behaviour and physical activity (PA) were considered in a cross-sectional sample of Portuguese adolescents. The sample included 362 youth aged 13-16 years (165 males, 197 females) from urban and rural regions of the Portuguese midlands. CRF was assessed with the 20-m shuttle-run test. An uniaxial accelerometer was used to obtain five consecutive days of activity behaviours including time being sedentary. Pearson correlations and logistic regression analysis were used to examine relationships among variables. Rural adolescents were less active than their urban peers over the weekend. Both rural and urban youth with higher levels of CRF had a lower relative risk of being overweight/obese. The observations indicate important associations between weight status and CRF in both rural and urban Portuguese adolescents. In addition, place of residence has an important impact on weight status of this sample of adolescents.

Prediction of adult height in girls: the Beunen-Malina-Freitas method

The purpose of this study was to validate and cross-validate the Beunen-Malina-Freitas method for non-invasive prediction of adult height in girls. A sample of 420 girls aged 10-15 years from the Madeira Growth Study were measured at yearly intervals and then 8 years later. Anthropometric dimensions (lengths, breadths, circumferences, and skinfolds) were measured; skeletal age was assessed using the Tanner-Whitehouse 3 method and menarcheal status (present or absent) was recorded. Adult height was measured and predicted using stepwise, forward, and maximum R (2) regression techniques. Multiple correlations, mean differences, standard errors of prediction, and error boundaries were calculated. A sample of the Leuven Longitudinal Twin Study was used to cross-validate the regressions. Age-specific coefficients of determination (R (2)) between predicted and measured adult height varied between 0.57 and 0.96, while standard errors of prediction varied between 1.1 and 3.9 cm. The cross-validation confirmed the validity of the Beunen-Malina-Freitas method in girls aged 12-15 years, but at lower ages the cross-validation was less consistent. We conclude that the Beunen-Malina-Freitas method is valid for the prediction of adult height in girls aged 12-15 years. It is applicable to European populations or populations of European ancestry.

Modelling developmental changes in repeated-sprint ability by chronological and skeletal ages in young soccer players

This study investigated the influence of chronological (CA) and skeletal ages (SA), anthropometry, aerobic endurance and lower limb explosive strength on developmental changes in repeated-sprint ability (RSA) in soccer players aged 11-17 years. Participants were annually followed over 5 years, resulting in 366 measurements. Multilevel regression modelling analysed longitudinal data aligned by CA and SA (Model 1 and 2, respectively). After diagnosing for multicollinearity, it was possible to predict RSA with 2-level hierarchical models [Model 1 (CA as Level 2 predictor): Log-Likelihood=1,515.29, p<0.01; Model 2 (SA as Level 2 predictor): Log-Likelihood=1,513.89, p<0.01]. Estimating sum of sprints for young soccer players are given by equations: sum of sprints=84.47 - 1.82 × CA + 0.03 × CA2 - 0.05 × aerobic endurance - 0.10 × lower limb explosive strength -0.09 × fat-free mass + 0.13 × fat mass (Model 1); 73.58 - 0.43 × SA - 0.05 × aerobic endurance - 0.10 × lower limb explosive strength - 0.08 × fat-free mass - 0.45 × training experience + 0.13 × fat mass (Model 2). The models produced performance curves that may be used to estimate individual performance across adolescent years. Finally, the validity of each model was confirmed based on corresponding measurements taken on an independent cross-sectional sample.

Professor James M. Tanner and the sport sciences

BACKGROUND

Although Tanner was not directly involved in physical education or the sport sciences, several of his papers addressed issues related to research in the area.

AIM

To consider the implications of selected papers and research projects for the sport sciences. PAPERS AND IMPLICATIONS: Several early papers addressed ratio standards, somatotype and total cholesterol, and anthropometric and somatotype changes associated weight training and cessation of training in young adult men. The papers have, respectively, implications for current studies of allometric scaling, physique and risk factors for cardiovascular and metabolic complications, and responses to training. The survey of athletes at the 1960 Rome Olympic Games not only added to the literature but to some extent also set the stage for subsequent surveys of Olympic athletes in 1968, 1972 and 1976. Although not directly involved in the mixed-longitudinal study of Training of Youth Athletes (TOYA) in several sports, it was conducted in his department. Results from TOYA indicated no influence of systematic training for sport on growth in height, young adult height and sexual maturation. Growth at Adolescence was also a fixture in many graduate programs.

CONCLUSION

Though not a sport scientist, Tanner contributed directly and indirectly to the field.

Interrelationships among invasive and non-invasive indicators of biological maturation in adolescent male soccer players

The relationships among indicators of biological maturation were evaluated and concordance between classifications of maturity status in two age groups of youth soccer players examined (11-12 years, n = 87; 13-14 years, n = 93). Data included chronological age (CA), skeletal age (SA, Fels method), stage of pubic hair, predicted age at peak height velocity, and percent of predicted adult height. Players were classified as on time, late or early in maturation using the SA-CA difference, predicted age at peak height velocity, and percent of predicted mature height. Factor analyses indicated two factors in players aged 11-12 years (maturity status: percent of predicted mature height, stage of pubic hair, 59% of variance; maturity timing: SA/CA ratio, predicted age at peak height velocity, 26% of variance), and one factor in players aged 13-14 years (68% of variance). Kappa coefficients were low (0.02-0.23) and indicated poor agreement between maturity classifications. Spearman rank-order correlations between categories were low to moderate (0.16-0.50). Although the indicators were related, concordance of maturity classifications between skeletal age and predicted age at peak height velocity and percent predicted mature height was poor. Talent development programmes call for the classification of youth as early, average, and late maturing for the purpose of designing training and competition programmes. Non-invasive indicators of maturity status have limitations for this purpose.

Body size, skeletal maturity, and functional characteristics of elite academy soccer players on entry between 1992 and 2003

Secular changes in body size, estimated fatness, skeletal maturation, and functional characteristics of youth soccer players on entry into an elite academy between 1992 and 2003 were compared. Annual selections grouped across time (1992-1995, 1996-1998, 1999-2003), playing position (goalkeeper, defender, midfielder, forward), and by eventual status in the sport (professional, non-professional) were compared. Data for 158 players (age 13.4 ± 0.4 years) at entry into the academy included skeletal age (Greulich-Pyle method), height, weight, relative fatness, four field tests of functional capacities (aerobic, anaerobic, power, speed), and quadriceps concentric strength of the dominant and non-dominant legs. MANCOVA with age as the covariate and chi square were used for comparisons across years. With few exceptions (but notably estimated [V·]O(2max)), results for player size, functional characteristics, and skeletal maturation did not differ among years. Distributions of players by skeletal maturity status and within each playing position also did not differ between years. Although related research has suggested that the anthropometric characteristics of professional players and demands of contemporary professional soccer competition increased over this period, the size, maturity, and functional characteristics of youth players on entry to an elite academy and of graduates who eventually played soccer as professionals generally did not change across annual selections from 1992 to 2003. The results suggest a lack of change in selection philosophies and practices of coaches involved in recruiting players for the academy, which in turn is reflected in consistency of specific evaluation criteria employed over the decade considered.

Longitudinal predictors of aerobic performance in adolescent soccer players

BACKGROUND

The importance of aerobic performance in youth soccer is well established. The aim of the present study was to evaluate the contributions of chronological age (CA), skeletal age (SA), body size, and training to the longitudinal development of aerobic performance in youth male soccer players aged 10 to 18 years.

MATERIAL AND METHODS

Players (n=83) were annually followed up during 5 years, resulting in an average of 4.4 observations per player. Decimal CA was calculated, and SA, stature, body weight, and aerobic performance were measured once per year. Fat-free mass (FFM) was estimated from age- and gender-specific anthropometric formulas, and annual volume training was recorded. After testing for multicollinearity, multilevel regression modeling was used to analyze the longitudinal data aligned by CA and SA (Model 1 and 2, respectively) and to develop aerobic performance scores.

RESULTS

The following equations provide estimations of the aerobic performance for young soccer players: ŷ(Model 1 [deviance from the null model =388.50; P<0.01]) =57.75+9.06×centered CA-0.57×centered CA(2)+0.03×annual volume training and ŷ(Model 2 [deviance from the null model=327.98; P<0.01])=13.03+4.04×centered SA-0.12×centered SA(2)+0.99×FFM+0.03×annual volume training.

CONCLUSIONS

The development of aerobic performance in young soccer players was found to be significantly related to CA, biological development, and volume of training.

Assessment of reliability in isokinetic testing among adolescent basketball players

BACKGROUND

The reproducibility of day-to-day testing of isokinetic concentric and eccentric muscular actions among adolescent basketball players aged 14 to 16 years and relationships of mean within-subject variation in two isokinetic testing sessions with chronological age, biological maturation (estimated age at peak height velocity), training experience, body size, lower-body morphology, and initial strength performance were evaluated.

MATERIAL AND METHODS

The sample included 27 basketball players who completed replicate test sessions of 5 repetitions of reciprocal concentric and eccentric knee extensions and flexions at 60º s(-1). A randomly selected subsample of 8 players completed a third testing session to confirm reliability estimates.

RESULTS

Coefficients of variation (CV) between sessions 1 and 2 ranged from 8.1% to 17.4%, and intraclass coefficients (ICCs) ranged from 0.72 to 0.89. For sessions 1 and 3, CVs ranged from 3.9% to 6.0%, and ICCs ranged from 0.95 to 0.99. The initial level of strength of eccentric knee flexion (r=-0.43) and eccentric knee extension (r=-0.42) were correlated (P<0.05) with eccentric knee extension within-variation between two sessions. Training experience (r=-0.37, P<0.05) and initial values of concentric knee flexion (r=-0.62, P<0.01) were correlated with concentric knee flexion within-subject differences. Within-subject variation of eccentric knee extension was correlated (P<0.05) with chronologic age (r=0.41), estimated age at peak height velocity (r=-0.38), body size (r=0.41 to 0.47), and leg volume (r=0.39).

CONCLUSIONS

Familiarization sessions may improve the reliability of concentric and eccentric knee isokinetic strength testing at 60º s(-1) in adolescent basketball players. Age, maturity status, and training experience of young athletes should be considered when testing knee isokinetic strength at 60º s(-1).

Age-related variation of anaerobic power after controlling for size and maturation in adolescent basketball players

BACKGROUND

Adolescence is characterized by increments in body size and physical performance. Short bursts of maximal intensity, requiring anaerobic metabolism, are important in many team sports including basketball.

AIM

Variation of anaerobic power of adolescent basketball players (n = 93, 14-16 years) in relation to years before and after estimated age at peak height velocity (PHV) and variation in body size was considered.

METHODS

The cross-sectional study included chronological age, estimated age at PHV, training experience; stature, body mass (BM), free-fat mass (FFM) and estimated lower-limb volume (LLV) by anthropometry; and short-term power outputs derived from the Wingate Anaerobic Test (WAnT). Based on proportional allometric modeling, power outputs were partitioned for biological maturity status and size variables. Pearson correlations were used to estimate the associations between distance to PHV (maturity offset) and training experience with absolute and scaled estimates of short-term power.

RESULTS

Absolute WAnT increased linearly (PP, r = 0.72; MP, r = 0.74) through the interval of rapid growth of the adolescent spurt. Increments were related mainly to BM and muscle mass. Nevertheless, a residual significant positive influence of chronological age per se on maximal short-term power outputs remained independent of body size.

CONCLUSION

Allometric modelling to partition size may reveal other potentially meaningful factors in the development of short-term performance in adolescent athletes.

Correlates of physical activity in Portuguese adolescents from 10 to 18 years

This study examined the association between demographic [age, sex, socioeconomic status (SES)] and socio-cultural [father, mother, sibling physical activity (PA); peers and physical education teacher influences] correlates and low, moderate and high levels of PA among Portuguese adolescents aged 10-18 years. A total of 3352 males and females attending basic and secondary schools, their parents and siblings were sampled across four regions of Portugal. PA was assessed with a psychometrically validated questionnaire. Multinomial logistic regression was used. Age was positively related with moderate and high PA. Boys and adolescents of high SES were more likely to participate in moderate and high PA. Adolescents were more likely to participate in high PA when theirs mother and sibling(s) also participated. Peers had a positive influence on participation in moderate and high PA, while physical education teachers did not have an influence. The results indicated that demographic and socio-cultural correlates--in particular age, sex, SES, mother and sibling PA, and peer influence--were significantly associated with adolescent PA. These results also suggested that interventions should focus on girls and low SES adolescents who face higher risk of inactivity.

Cross-validation and reliability of the line-drill test of anaerobic performance in basketball players 14-16 years

This study evaluates the validity and reliability of the line-drill (LD) test of anaerobic performance in 76 male basketball players 14.0-16.0 years of age. The Wingate Anaerobic Test (WAnT) was used as the reference for anaerobic performance. Wingate Anaerobic Test and LD test were moderately correlated (0.39 and 0.43, p < 0.01). Estimated age at peak height velocity (APHV) was moderately, negatively, and significantly (p < 0.01) correlated with WAnT peak (r = -0.69) and mean power (r = -0.71); earlier-maturing players had greater anaerobic power. Training experience was not associated with anaerobic performance, but chronological age (CA) and estimated APHV were significant covariates of the LD test (p < 0.05). National players were better than local players on the LD test (p < 0.01) after controlling for CA and body size. Short-term reliability of the LD test (n = 12, 1-week interval) was good: technical error of measurement = 0.44 seconds (95% confidence interval [CI] 0.31-0.75 seconds), intraclass correlation coefficient = 0.91 (95% CI 0.68-0.97), and coefficient of variation = 1.4% (95% CI 1.0-2.3%). Although the relationship between the LD test and WAnT was moderate, the LD test effectively distinguished local- and national-level adolescent basketball players. In contrast to WAnT, the LD test was not influenced by estimated biological maturity status. Thus, the LD test may be suitable for field assessment of anaerobic performance of youth basketball players.

Correlates of physical activity and inactivity in urban Mexican youth

OBJECTIVES

To evaluate correlates of physical activity in Mexico City school youth.

METHODS

A cross-sectional survey was conducted with 1,004 school youth (490 males and 514 females), 9-18 years of age resident in Mexico City. Age, height, body mass index (BMI), socioeconomic status (SES), time viewing television and playing video games (physical inactivity), and perceived sport/physical activity status of mother and father were evaluated as potential correlates of physical activity [Physical Activity Questionnaire (PAQ)]. Multiple linear regression analyses (backward elimination) by age group and sex were used.

RESULTS

Physical activity declined in older adolescents, while differences between the two younger age groups were minimal. Television time showed a similar tendency. Overall, fathers were perceived as being active in sport/physical activity more frequently than mothers. Significant predictors of activity differed by age group and sex. For the total sample, age (negative) and perceived sport/activity status of the mother (positive) were significant predictors of the PAQ in boys, and age and the BMI (negative) and height and perceived sport/activity status of both parents (positive) were significant predictors for girls. Age (negative) was the main predictor for inactivity in both males and females.

CONCLUSIONS

Potential correlates of physical activity and inactivity considered in this analysis were limited and accounted for relatively little of the variance in physical activity. The role of perceived sport/activity of the parents, especially among younger boys and girls, is particularly of interest and merits more detailed study. Nevertheless, many other variables also need to be considered.

Physical fitness of normal, stunted and overweight children 6-13 years in Oaxaca, Mexico

BACKGROUND/OBJECTIVE

The objective of this study is to compare the growth and physical fitness of normal, stunted and overweight/obese (owt/ob) Oaxaca children 6-13 years.

SUBJECTS/METHODS

This study was a cross-sectional, included 688 school children (grades 1-3, 4-6), aged 6-13 years, from an indigenous rural community (n=361) and colonia popular (n=327) in Oaxaca, southern Mexico.

MEASUREMENTS

Anthropometry-weight, height, sitting height, limb circumferences, skinfolds. Derived-body mass index, sitting height/height ratio, leg and step lengths, limb muscle areas, sum of skinfolds. Physical fitness-sit and reach, sit-ups, distance run, grip strength, standing long jump, 35 yard dash. Physical activity-steps to and from school, household chores, sports participation.

ANALYSIS

Normal-not stunted, not owt/ob; stunted-not owt/ob; and owt/ob-not stunted were compared with multivariate analysis of covariance controlling for age. Two children were stunted and owt/ob, and were excluded.

RESULTS

Age-adjusted means for body size, muscularity, adiposity and grip strength showed a gradient, owt/ob>normal>stunted in both sexes and grade levels (P<0.001). Relative position of stunted and owt/ob children was reversed for strength per unit mass. Stunted and normal children ran a greater distance than owt/ob children (P<0.05). Normal, stunted and owt/ob children did not differ consistently in other fitness items and indicators of activity and inactivity.

CONCLUSION

Size, muscularity, fatness and strength differed significantly, owt/ob>normal>stunted, but owt/ob children had less strength per unit mass and poorer endurance. Normal and stunted children did not differ consistently in fitness. Physical activity and television time did not differ among the three groups.