Background:Popular media, health experts and researchers talk about a paediatric 'obesity epidemic' with exponentially increasing rates of obesity and overweight. However, some recent reports suggest that prevalence may have plateaued. This study examined trends in the prevalence of Australian childhood overweight and obesity since 1985. Specifically, it aimed to determine whether there have been (a) overall increases in average body mass index (BMI),(b) differential patterns of change within age groups and (c) increases in BMI within each weight-status category.Method:Forty-one Australian studies of childhood weight status conducted between 1985 and 2008 were reviewed. The studies included data on 264 905 Australians aged 2-18 years, with raw data being available on 70 758 children (27%). Children were classified as overweight or obese based on BMI using the criteria of Cole et al.(BMJ, 2000). The prevalence estimates were adjusted for age and sex, and plotted against measurement year using Lowess plots and two-linear-segment models. Where raw data were available, BMI z-scores (UK 1990 standard) were plotted against measurement year for all children and children in various age groups. Lowess plots and two-linear-segment models were used to assess secular trends in BMI z-scores pre- and post-1996 within age, gender and weight-status categories.Results:There has been a plateau, or only slight increase, in the percentage of boys and girls classified as overweight or obese, with almost no change over the last 10 years. In boys and girls, prevalence rates have settled around 21-25% for overweight and obesity together, and 5-6% for obesity alone. Similar trends were found for BMI z-scores. These patterns were fairly consistent across the age span. Within each weight-status category, average BMI has not increased.Conclusions:Although levels of Australian paediatric overweight remain high, the prevalence of overweight and obesity seems to have flattened and has not followed the anticipated exponential trajectory.International Journal of Obesity advance online publication, 13 October 2009; doi:10.1038/ijo.2009.211.

Departures from perfect bilateral symmetry are thought to mirror an organism's ability to maintain developmental homeostasis. There is evidence showing that symmetry is negatively correlated with evolutionary and physical fitness. The purpose of this study was to determine the relationship between symmetry and health-related physiological characteristics in males and females. Forty-six male and female subjects participated in this study. Both facial and anthropometric traits were investigated for deviations from perfect bilateral symmetry. After measurements were made the subjects were tested on a range of physiological variables. There was no pattern of consistent significant correlations between fluctuating asymmetry and the physiological variables across all traits, and poor inter-correlations between the fluctuating asymmetries measured at different sites. The study failed to confirm the hypothesis that symmetric individuals were physiologically fitter when compared to their asymmetric counterparts.

Background/Objectives:There are abundant data on secular trends in the body mass index (BMI) of children. However, BMI is an imperfect index of fatness, whereas skinfold thicknesses provide a more direct measure. This study aims to meta-analyse historical studies of triceps and subscapular skinfold thicknesses in young people aged 0-18 years in developed countries.Subjects/Methods:A total of 154 studies conducted between 1951 and 2003 were analysed, covering 2390 reports at the age x sex x country level, and more than 458 547 young people from 30 developed countries. Percentage body fat (% BF) was estimated using the Slaughter equations. The distribution of fat on the body was indexed by the triceps/subscapular (T/S) ratio. The skewness of skinfold distributions was operationalized by the coefficient of variation and the mean-median difference.Results:There have been increases in triceps and subscapular skinfold thicknesses, at the rate of 0.4-0.5 mm per decade over the period 1951-2003.% BF has been increasing at the rate of 0.9% BF per decade. The distribution of fat on the body, as indexed by the triceps/subscapular (T/S) ratio, has become more central. There has been an increasing positive skew in the distribution of subcutaneous fat thickness in the population.Conclusions:These trends describe very unfavourable changes in the body composition of young people, foreshadowing a potential increase in the incidence of cardiovascular and metabolic disease.European Journal of Clinical Nutrition advance online publication, 18 February 2009; doi:10.1038/ejcn.2009.7.

Aim: To quantify the global changes in anaerobic fitness (operationalized as power and speed test performance) of children and adolescents. Methods: Following an extensive review of the literature, 32 studies examining secular changes in power and speed test performance of children and adolescents were analysed. Performance changes were calculated at the country x age x sex x test level using weighted least-squares regression, and were expressed as a percentage of the weighted mean value for all data points in the regression. Negative values indicated performance declines, and positive values indicated improvements. Results: Changes in power (n=20 802 925) and speed (n=28 320 308) test performance were calculated for 6-19 year olds from 27 countries and five geographical regions, for the period 1958-2003. Overall, power and speed test performances improved at +0.03% and +0.04% per annum, respectively. Performance changes were remarkably similar for boys and girls, and children and adolescents, and somewhat similar for different geographical regions, and high and low income economies. The pattern of change was reasonably consistent over time. Conclusion: The relative stability in anaerobic fitness test performances in recent decades could be due to the negating effects of increases in fat mass and fat-free mass on anaerobic performance.

The purpose of the present article is to identify the most appropriate method of scaling VO2max for differences in body mass when assessing the energy cost of time-trial cycling. The data from three time-trial cycling studies were analysed (N = 79) using a proportional power-function ANCOVA model. The maximum oxygen uptake-to-mass ratio found to predict cycling speed was VO2max(m)(-0.32) precisely the same as that derived by Swain for sub-maximal cycling speeds (10, 15 and 20 mph). The analysis was also able to confirm a proportional curvilinear association between cycling speed and energy cost, given by (VO2max(m)(-0.32))0.41. The model predicts, for example, that for a male cyclist (72 kg) to increase his average speed from 30 km h(-1) to 35 km h(-1), he would require an increase in VO2max from 2.36 l min(-1) to 3.44 l min(-1), an increase of 1.08 l min(-1). In contrast, for the cyclist to increase his mean speed from 40 km h(-1) to 45 km h(-1), he would require a greater increase in VO2max from 4.77 l min(-1) to 6.36 l min(-1), i.e. an increase of 1.59 l min(-1). The model is also able to accommodate other determinants of time-trial cycling, e.g. the benefit of cycling with a side wind (5% faster) compared with facing a predominately head/tail wind (P<0.05). Future research could explore whether the same scaling approach could be applied to, for example, alternative measures of recording power output to improve the prediction of time-trial cycling performance.

This paper summarizes 41 reports on the height and mass of Australian children aged between 5.00 and 16.99 years between 1899 and 1999. In all, data on 644,613 children were collated, including individual data on 68,196 children. After primary data treatment to correct for methodological and statistical artifacts, regressions were calculated to quantify the rate of change of height and mass over time. Distributional analysis was used to probe for changes in skewness of mass values, indicative of differentially greater increases at higher percentiles. In addition, studies reporting skin fold measurements were analyzed to assess changes in subcutaneous adiposity since 1976. The results show that height has been increasing at a rate of about 1.02 cm.decade(-1), and mass at a rate of about 0.99 kg.decade(-1). The height and mass of children continue to increase, after a slowing down in the rate of increase between 1950 and 1980. Increases in mass at the higher percentiles have been much greater than at lower percentiles, particularly since the mid-1980s, suggesting that the incidence of obesity is increasing in Australian children. Furthermore, a steady linear increase in subcutaneous skin fold thicknesses since 1976 suggests that the overall level of fatness is increasing in Australian children. These findings indicate that Australian children are following trends becoming evident elsewhere in the developed world, and that we may see an increasingly large subset of increasingly obese children in the early years of the 21st century.

This study investigated using reticulocyte (retic) parameters as indirect markers of human recombinant erythropoietin (r-HuEPO) abuse in elite athletes. Absolute reticulocyte count (# retic), the per cell haemoglobin content of reticulocytes (CHr), reticulocyte haemoglobin mass per litre of blood (RetHb) and red blood cell:reticulocyte haemoglobin (RBCHb:RetHb) ratio were assessed using flow cytometry. Venous blood was drawn from 155 elite athletes from six sports during regular training to establish reference ranges (95% confidence interval) for these parameters. The reference ranges were compared with those of a non-athletic population (n = 23), four groups of athletes (n = 24) before and after exposure to simulated altitudes (2,500-3,000 m for 11-23 nights), two groups of elite cyclists (n = 13) before and after four weeks of training at natural altitude (1,780 and 2,690 m), and with those of non-athletic subjects from a separate study (n =24) before and 1-2 days after they were injected with 1,200 U x kg(-1) r-HuEPO over a 9-10 day period. Generally the changes induced by r-HuEPO injection exceeded by approximately 100% the magnitude of the changes associated with natural altitude exposure. Simulated altitude exposure did not significantly alter the reticulocyte parameters. From the sample of 155 non-users and 24 r-HuEPO users, the population mean and variance, as well as the 95% confidence limits for the population mean and population variance, were estimated. Relative to arbitrarily chosen cut-off levels, the confidence limits for the rate of true positives and rate of true negatives were also calculated. Based on the lowest rate of false positives and highest rate of true positives, the best discriminator between r-HuEPO users and non-users was # retic, marginally superior to RBCHb: RetHb ratio and RetHb. At a cut-off for # retic of 221 x 10(9)x L(-1) we could be 95% sure that we would find no more than 7 false positives in every 100,000 tests. We would expect to pick up 51.8% of users, and could be 95% sure of picking up at least 38% of current or recent users. This result highlights the potential power of retic parameters for detecting r-HuEPO abuse among athletes. However, the efficacy of these cut-offs for detecting r-HuEPO abuse is unknown if an athlete is a chronic user or stops using r-HuEPO several weeks before being tested.

Australian football has undergone considerable change over the past century. This evolution seems to have accelerated more recently since the introduction and major influence of the media, increased professionalism and the start of a national competition. In this study we have attempted to quantify the evolution in game 'style' by measuring events during elite football games (from video analysis) and gathering physical information on players involved at the highest level. These data are important to gain insight into the game demands so that player preparation may be enhanced and when predicting the nature of the game in the future. Understanding the patterns of play within the game may also be useful when assessing the possible impact of rule changes, for example, increasing the number of interchange players on the potential for injury. Four games were selected, one from each of the past 4 decades to determine the rate at which specific, measurable events occurred in the games. Height and mass data on players were also obtained from official records of registered players in the VFL/AFL competitions. The results indicate the 'speed' of the game has approximately doubled in the period 1961-1997. The proportion of the total game which involves 'play' time has been reduced significantly while breaks in play are more frequent and longer. Despite this pattern, however, the average game tempo has increased along with player height and mass and we present a case which suggests these are likely determinants of the increased incidence of player injuries and lost match time.

The effects of exercise distribution on lymphocyte count, lymphocyte subpopulations and plasma cortisol concentration in peripheral blood were assessed in 19 healthy subjects. The subjects were randomly divided into group A (n = 10) or group B (n = 9) according to exercise distribution. Both groups underwent a 10-week programme involving 5 x 2-week blocks: baseline (B), training period 1 (TP1), stabilisation 1 (S1), training period 2 (TP2), and stabilisation 2 (S2). During B, S1 and S2 normal training was undertaken. During TP1 and TP2 the subjects increased the amount of training by 50% in week 1 and by 100% in week 2. During TP1 subjects in group A exercised 6 days.week-1, while during TP2 these subjects exercised on 3 alternate days.week-1, but doubled the duration of each training session. The subjects in group B reversed this training order. Blood was collected 36-42 h following exercise period B, and at the end of periods TP1, S1, TP2 and S2, and also 12-18 h following completion of exercise at the end of TP1 and TP2. There were no significant differences (P > 0.05) between the 6 day.week-1 programme and the 3 alternate day.week-1 programme in total lymphocyte count, CD3+, CD4+, CD8+, CD16+, or CD19+ cells, the CD4:CD8 ratio, HLA-DR+(activated) T cells or plasma cortisol concentrations. Following both TP1 and TP2 there was a nonsignificant decrease in lymphocyte subpopulations. However following both S1 and S2 (baseline training) there was a significant increase in total lymphocyte count, CD3+, CD4+ and CD8+ lymphocytes. The S2 variables statistically significant from B were: total lymphocyte count (P < 0.01), CD3+ T-cells and percentage of circulating lymphocytes (P < 0.01), CD4+ cells (P < or = 0.0001), CD8+ cells (P < 0.05), and HLA-DR+(activated) T-cells (P < 0.05). The results indicated that provided the amount of exercise is constant for a given period, then exercise distribution is not a critical variable in the alteration of lymphocyte subpopulations that may occur in response to overload training. However 2 weeks of overload training followed by 2 weeks of active recovery (baseline) training may induce an increase in the lymphocyte count.

Infrared (IR) thermometers (FirstTemp 2000A, Intelligent Medical Systems, California) were used to monitor tympanic temperature (Tty) in 12 collapsed fun-runners suspected of suffering exertion-induced heat exhaustion (EIHE). Rectal temperature (Tre) was monitored via digital clinical thermometers. Conditions during the fun-run and in the field treatment centre were cool (air temperature 16-18 degrees C, relative humidity 60-65%). On admission, Tty was (mean +/- SEM) 1.2 +/- 0.3 degrees C lower than Tre. For admission plus subsequent monitoring data pooled, although Tty correlated significantly with Tre (r = 0.86, p < 0.001), mean Tty (37.4 +/- 0.2 degrees C) was significantly lower (p < 0.01) than mean Tre (38.4 +/- 0.4 degrees C). Cotton wool ear pads, applied to 10 of the runners on admission to minimise environmental effects on Tty, did not significantly improve the IR monitoring. A Tty > or = 37.1 degrees C predicted a Tre > or = 38 degrees C (an established diagnostic criterion for EIHE) with a sensitivity of 0.93 and a specificity of 0.63. These data indicate that IR tympanic thermometry, when utilised in cool environments, can result in misdiagnosis of heat exhaustion. Although IR thermometry shows some promise as a rapid, non-invasive means of monitoring core temperature, it should not be used in the diagnosis and treatment of heat exhaustion unless further research validates the method.

The article presents the current performance capacity in 11-15 year old Dutch adolescents who participated in an incremental cycle test (n = 509) and or in a shuttle run test (N = 1,198). Cycle test results increased significantly with age in both genders, also after normalization to body weight. Shuttle run test results increased significantly with age only in boys. Compared with previous data, the absolute performance capacity in the cycle tests was comparable to data from 15 years ago, whereas the performance capacity normalized to kg body weight and the shuttle run test results seem to be fairly lower compared with the former data.

It has been argued that motivation significantly affects the measurement of aerobic capacity when using field tests with children. In this study, the impact of generalized self-efficacy on performance (Stage Completed) in the Léger shuttle run is examined in a cohort of children (N = 2,245, 9.38 +/- 0.52 years old) in Grade 4 from 75 elementary schools. Children completed the Children's Self-perceptions of Adequacy in and Predilection for Physical Activity scale (CSAPPA) to establish levels of generalized self-efficacy toward physical activity, were measured for height and weight, and then completed the Léger Shuttle run to predict aerobic capacity. Regression analysis was used to study the impact of self-efficacy on test performance. After adjusting for age, gender, and BMI, two of the three CSAPPA factor subscales, higher perceived adequacy regarding physical activity (beta = 0.196, P < 0.001) and greater predilection to select physical over sedentary activities (beta = 0.123, P < 0.001), were independently associated with better test performance as indicated by stage completed. Together, self-efficacy accounted for 9% of the total variation in Léger shuttle run performance. A significant interaction between BMI and perceived adequacy was found (beta =-0.106, P < 0.005). Children with both high BMI scores and below average perceived adequacy had the poorest performance results. Generalized self-efficacy, as measured by the CSAPPA, is significantly related to Léger shuttle run performance. Moreover, self-efficacy influences the relationship between other known factors affecting test performance (BMI), suggesting that self-perception of ability/competence has a complex effect on test performance. These results illustrate the importance of considering psychological factors when interpreting physiologic assessments in children. Am. J. Hum. Biol., 2007.(c) 2007 Wiley-Liss, Inc.

Background The Movement Assessment Battery for Children (Movement ABC) was developed as a means of identifying those at risk of motor impairment. This test has been widely adopted as a means of assessing Australian children, but no attempt has been made to test the validity of its normative data for Australian samples. This study examines the 4- and 5-year-old Australian data in comparison with the Movement ABC age norms. Additionally, a 3-year-old sample was tested to determine if the test is suitable for discriminating motor performance in this age group. Methods Representative samples of 3-, 4- and 5-year-old children from two Australian cities (Sydney and Perth) were tested on the Movement ABC band-one tests and the results compared with 4- and 5-year norms. Results There was significant age-related change in performance across the Australian samples with significant gender effects on some tasks. The Australian 4-year-old children performed better than the American sample on most tests, but this difference had disappeared by 5 years. Conclusion The results indicate that the Movement ABC is a useful tool in discriminating among pre-school Australian children as young as 3 years of age. The differences between Australian and American children indicate that further studies comparing other age groups are warranted, but the differences did not appear to be sufficiently large to have clinical significance.

Concerns about the value of physical testing and apparently declining test performance in junior basketball players prompted this retrospective study of trends in anthropometric and fitness test scores related to recruitment age and recruitment year. The participants were 1011 females and 1087 males entering Basketball Australia's State and National programmes (1862 and 236 players, respectively). Players were tested on 2.6 +/- 2.0 (mean +/- s) occasions over 0.8 +/- 1.0 year. Test scores were adjusted to recruitment age (14 - 19 years) and recruitment year (1996 - 2003) using mixed modelling. Effects were estimated by log transformation and expressed as standardized (Cohen) differences in means. National players scored more favourably than State players on all tests, with the differences being generally small (standardized differences, 0.2 - 0.6) or moderate (0.6 - 1.2). On all tests, males scored more favourably than females, with large standardized differences (>1.2). Athletes entering at age 16 performed at least moderately better than athletes entering at age 14 on most tests (standardized differences, 0.7 - 2.1), but test scores often plateaued or began to deteriorate at around 17 years. Some fitness scores deteriorated over the 8-year period, most notably a moderate increase in sprint time and moderate (National male) to large (National female) declines in shuttle run performance. Variation in test scores between National players was generally less than that between State players (ratio of standard deviations, 0.83 - 1.18). More favourable means and lower variability in athletes of a higher standard highlight the potential utility of these tests in junior basketball programmes, although secular declines should be a major concern of Australian basketball coaches.

Aims: This study quantifies the cross-sectional and longitudinal relationships between young people's fatness (BMI, skinfold thickness) and fitness (performance on tests of aerobic fitness). Background: Over the last 20-30 years, young people have become fatter and less fit. It is likely that the decline in fitness is largely due to increases in fatness. There are strong mechanistic connections; within cohorts, variability in fatness accounts for about 20% of variability in running performance; there is a strong correlation between overweight prevalence and relative fitness across specific cohorts from different countries; and secular declines in fitness coincide temporally with increases in BMI. Methods: Australians aged 10-12 years tested in 1985 were matched for age, sex, BMI and triceps skinfold thickness with their counterparts tested in 1997 (n = 279 matched pairs), and 12-15 year-old tested in 1995-1996 were matched with their counterparts tested in 1999-2000 (n = 2,834 matched pairs). Performance differences on running tests in the matched datasets were compared with performance differences in the complete (unmatched) datasets. Results: Performance differences persisted even when young people were matched for fatness. Matching for fatness reduced overall performance differentials by 29-61%. Other factors such as reduced physical activity and subsequent training effect are likely to have contributed to the decline.

There is accumulating evidence of worldwide declines in cardiorespiratory endurance (CRE) among children. To date, few studies have focused on trends in distributional characteristics of CRE performance. This study analyzed 1985 and 1997 samples of Australian children on the 1.6 km run/walk test, using a variety of descriptive and inferential statistics to compare distributions of average running speed among 10- to 11-year-olds. The analysis was conducted on 965 boys and 935 girls from 1985, and 661 boys and 553 girls from 1997. Among boys there was a significant increase in the coefficient of variation of average completion times, with a marked decrease in negative skew. This was largely attributable to the largest declines occurring in the middle percentiles, with relatively smaller declines at low (<5th) and high (>90th) percentiles. The bulk of the scores have shifted towards the left side of the distribution, reducing the skew. Among girls the distributional trends were different; there was little change in 'scatter' and skew of test scores, with declines in performance being relatively uniform across the distribution. These findings contrast with previous reports of greater declines among the lowest ranked performers on CRE tests. The observed declines in all percentiles other than the lowest and highest ranked boys suggest that mechanisms for declining fitness are widespread throughout the population and may reflect changes in environmental barriers and enablers of regular physical activity among Australian youth.