Temporal Trends in the Physical Fitness of Hong Kong Adolescents Between 1998 and 2015

Low physical fitness in adolescence is linked with increased cardiometabolic risk and early all-cause mortality. This study aimed to estimate temporal trends in the physical fitness of Hong Kong adolescents aged 12-17 years between 1998 and 2015. Physical fitness (9-min run/walk, sit-ups, push-ups, and sit-and-reach) and body size data in a total of 28,059 adolescents tested across five population-representative surveys of Hong Kong secondary school pupils, were reported. Temporal trends in means were estimated at the gender-age level by best-fitting sample-weighted linear regression, with national trends estimated by a post-stratified population-weighting procedure. Overall, there were small declines in 9-min run/walk (effect size (ES)=-0.29 (95%CI: -0.32, -0.26)) and sit-ups performance (ES=-0.24 (95%CI: -0.27, -0.21)), with negligible changes in push-ups and sit-and-reach performance. There were small concurrent increases in both mean height and body mass, with a negligible increase in sum of skinfolds. Trends in mean physical fitness and body size/were not always uniform across the population distribution. The small declines in mean 9-min run/walk and sit-ups performance for Hong Kong adolescents are suggestive of corresponding declines in cardiorespiratory fitness and abdominal/core endurance, respectively. Increased national health promotion strategies are required to improve existing trends.

Spatial Heterogeneity and Regional Clustering of Factors Influencing Chinese Adolescents' Physical Fitness

There is often significant spatial heterogeneity in the factors influencing physical fitness in adolescents, yet less attention has been paid to this in established studies. Based on the 2018 Chinese National Student Physical Fitness Standard Test data, this study uses a multi-scale, geographically weighted regression (MGWR) model combined with a K-means clustering algorithm to construct a spatial regression model of the factors influencing adolescent physical fitness, and to investigate the degree of spatial variation in the physical fitness of Chinese adolescents from a socio-ecological perspective of health promotion. The following conclusions were drawn: the performance of the youth physical fitness regression model was significantly improved after taking spatial scale and heterogeneity into account. At the provincial scale, the non-farm output, average altitude, and precipitation of each region were strongly related to youth physical fitness, and each influencing factor generally showed a banded spatial heterogeneity pattern, which can be summarized into four types: N-S, E-W, NE-SW, and SE-NW. From the perspective of youth physical fitness, China can be divided into three regions of influence: the socio-economic-influenced region, mainly including the eastern region and some of the central provinces of China; the natural-environment-influenced region, which mainly includes the northwestern part of China and some provinces in the highland region; and the multi-factor joint-influenced region, which mainly includes the provinces in the central and northeastern regions of China. Finally, this study provides syndemic suggestions for physical fitness and health promotion for youths in each region.

Trends in means and distributional characteristics of cardiorespiratory endurance performance for Italian children (1984-2010)

Cardiorespiratory endurance (CRE) is an important health marker. The aim of this study was to examine temporal trends of CRE performance for Italian children between 1984 and 2010. Using a repeated cross-sectional study design, 5303 CRE test results were available for 2520 children aged 11-13 years from a single Northern Italian middle-high school between 1984 and 2010. CRE was measured as 1000-m and 12-min run test performance. With adjustments for BMI, temporal trends in means were estimated using linear regression, with trends in distributional characteristics described visually and estimated as the ratio of coefficients of variation (CVs). There was a significant small increase in BMI (effect size (ES) [95%CI]: 0.40 [0.32, 0.48]) over the entire period. When adjusted for BMI, there were significant small to moderate declines in mean running speed (ES [95%CI]: 1000-m, - 0.34 [-0.39, - 0.29]); 12-min, - 0.65 [-0.70, - 0.60]). Declines were larger for boys compared to girls. Variability substantially increased over time (ratio of CVs: range, 1.7-2.9), with larger declines in children with low running speed compared to children with average or high running speed. Our findings may be important to public health because low CRE is significantly related to current and future health.

Geographical Variation in Physical Fitness Among Chinese Children and Adolescents From 2005 to 2014

Introduction: To examine the geographical variation in change in the levels of physical fitness from 2005 to 2014 among Chinese children and adolescents.

Methods: A total of 663,813 children 7 to 18 years of age with physical fitness data in 2005, 2010 and 2014, participated in the study. Physical fitness was assessed using six components, and their standardized scores were aggregated to form a summary physical fitness indicator (PFI).

Results: Over the study period, there was an increase in the proportion of high PFI (from 15.3% in 2005 to 19.0% in 2014, P_trend < 0.05) and a decrease in the proportion of low PFI (from 30.6 to 29.8%, P_trend < 0.05). Children and adolescents in the eastern provinces of China showed a high proportion of high PFI with an increasing trend over time, while those in the western provinces had a high proportion of low PFI with a decreasing trend over time (P < 0.05).

Conclusions: The comprehensive physical fitness among Chinese children showed an improved trend from 2005 to 2014. Region-specific interventions with priority policies could be useful to sustainably narrow geographical variation in Chinese children, especially in the western provinces.

A Systematic Analysis of Temporal Trends in the Handgrip Strength of 2,216,320 Children and Adolescents Between 1967 and 2017

OBJECTIVE

To estimate national and international temporal trends in handgrip strength for children and adolescents, and to examine relationships between trends in handgrip strength and trends in health-related and sociodemographic indicators.

METHODS

Data were obtained through a systematic search of studies reporting temporal trends in the handgrip strength for apparently healthy 9-17-year-olds, and by examining large national fitness datasets. Temporal trends at the country-sex-age level were estimated by sample-weighted regression models relating the year of testing to mean handgrip strength. International and national trends were estimated by a post-stratified population-weighting procedure. Pearson's correlations quantified relationships between national trends in handgrip strength and national trends in health-related/sociodemographic indicators.

RESULTS

2,216,320 children and adolescents from 13 high-, 5 upper-middle-, and 1 low-income countries/special administrative regions between 1967 and 2017 collectively showed a moderate improvement of 19.4% (95% CI 18.4-20.4) or 3.8% per decade (95% CI 3.6-4.0). The international rate of improvement progressively increased over time, with more recent values (post-2000) close to two times larger than those from the 1960s/1970s. Improvements were larger for children (9-12 years) compared to adolescents (13-17 years), and similar for boys and girls. Trends differed between countries, with relationships between national trends in handgrip strength and national trends in health-related/sociodemographic indicators negligible-to-weak and not statistically significant.

CONCLUSIONS

There has been a substantial improvement in absolute handgrip strength for children and adolescents since 1967. There is a need for improved international surveillance of handgrip strength, especially in low- and middle-income countries, to more confidently determine true international trends.

PROSPERO REGISTRATION NUMBER

CRD42013003657.

An Update on Secular Trends in Physical Fitness of Children and Adolescents from 1972 to 2015: A Systematic Review

BACKGROUND

There is evidence that physical fitness of children and adolescents (particularly cardiorespiratory endurance) has declined globally over the past decades. Ever since the first reports on negative trends in physical fitness, efforts have been undertaken by for instance the World Health Organization (WHO) to promote physical activity and fitness in children and adolescents. Therefore, it is timely to re-analyze the literature to examine whether previous reports on secular declines in physical fitness are still detectable or whether they need to be updated.

OBJECTIVES

The objective of this systematic review is to provide an 'update' on secular trends in selected components of physical fitness (i.e., cardiorespiratory endurance, relative muscle strength, proxies of muscle power, speed) in children and adolescents aged 6-18 years.

DATA SOURCES

A systematic computerized literature search was conducted in the electronic databases PubMed and Web of Science to locate studies that explicitly reported secular trends in physical fitness of children and adolescents.

STUDY ELIGIBILITY CRITERIA

Studies were included in this systematic review if they examined secular trends between at least two time points across a minimum of 5 years. In addition, they had to document secular trends in any measure of cardiorespiratory endurance, relative muscle strength, proxies of muscle power or speed in apparently healthy children and adolescents aged 6-18 years.

STUDY APPRAISAL AND SYNTHESIS METHODS

The included studies were coded for the following criteria: nation, physical fitness component (cardiorespiratory endurance, relative muscle strength, proxies of muscle power, speed), chronological age, sex (boys vs. girls), and year of assessment. Scores were standardized (i.e., converted to z scores) with sample-weighted means and standard deviations, pooled across sex and year of assessment within cells defined by study, test, and children's age.

RESULTS

The original search identified 524 hits. In the end, 22 studies met the inclusion criteria for review. The observation period was between 1972 and 2015. Fifteen of the 22 studies used tests for cardiorespiratory endurance, eight for relative muscle strength, eleven for proxies of muscle power, and eight for speed. Measures of cardiorespiratory endurance exhibited a large initial increase and an equally large subsequent decrease, but the decrease appears to have reached a floor for all children between 2010 and 2015. Measures of relative muscle strength showed a general trend towards a small increase. Measures of proxies of muscle power indicated an overall small negative quadratic trend. For measures of speed, a small-to-medium increase was observed in recent years.

LIMITATIONS

Biological maturity was not considered in the analysis because biological maturity was not reported in most included studies.

CONCLUSIONS

Negative secular trends were particularly found for cardiorespiratory endurance between 1986 and 2010-12, irrespective of sex. Relative muscle strength and speed showed small increases while proxies of muscle power declined. Although the negative trend in cardiorespiratory endurance appears to have reached a floor in recent years, because of its association with markers of health, we recommend further initiatives in PA and fitness promotion for children and adolescents. More specifically, public health efforts should focus on exercise that increases cardiorespiratory endurance to prevent adverse health effects (i.e., overweight and obesity) and muscle strength to lay a foundation for motor skill learning.

Levels of Physical Fitness and Weight Status in Children and Adolescents: A Comparison between China and Japan

This study compared the physical fitness level and weight status of children and adolescents in China and Japan. Children and adolescents aged 7–18 years were recruited (China: n = 5660; Japan: n = 5660). Physical fitness was assessed using seven core items—grip strength, 30-s sit-ups, standing long jump, sit-and-reach, 20-s repeated straddling, 20-m shuttle run test, and 50-m dash. A physical fitness index (PFI) was calculated by adding all items’ Z-scores. We conducted comparisons of PFI and its distribution, each physical fitness item, and weight status for individuals from China and Japan across all ages. The PFI was lower in China than in Japan for all age groups, with an especially large difference at age 18 years for boys (a difference of 9.05) and girls (a difference of 9.10) (p < 0.001). The same result was seen for the seven items. The PFI distribution for children and adolescents was more disperse among those in Japan than among those in China. Obesity prevalence was 2.84 times higher in China than in Japan. An inverted U-shaped relationship was observed between physical fitness and nutritional status. Children and adolescents showed markedly lower physical fitness and higher obesity prevalence in China than in Japan.

Temporal trend of cardiorespiratory endurance in urban Catalan high school students over a 20 year period

Background

Physical fitness is considered an important indicator of health in adolescents. However, in recent years several studies in the scientific literature have shown a considerable lower trend and an alarming worsening of the current adolescents’ physical condition when comparing with previous decades, especially in urban populations. The aim of the current study was to analyse the temporal trend in cardiorespiratory endurance (CRE) in urban Catalan adolescents over a 20-year period (1999–2019).

Methods

A cross-sectional analysis study considering the 20-m Shuttle Run test (SRT) results obtained in the last 20 years was carried out. 1,701 adolescents between 15 and 16 years old (914 boys and 787 girls) were divided into four groups, corresponding to consecutive periods of five years (Group 1: 1999–2004; Group 2: 2005–2009; Group 3: 2010–2014 and Group 4: 2015–2019). ANOVA was used to test the period effect on CRE and post hoc Bonferroni analysis was performed to test pairwise differences between groups (p < 0.05).

Results

Results showed a significantly lower performance in CRE in both sexes. The percentual negative difference was 0.67%, 9.6% and 7% for boys and 5.06%, 14.97% and 9.41% for girls, when comparing the performance in 20-m Shuttle Run test for the first period, respectively.

Conclusions

Results suggest that the physical fitness of Catalan urban adolescents is lower in both sexes when comparing the different analysed periods of time. Therefore, CRE adolescents should be improved in order to help to protect against cardiovascular disease and other health risks in adulthood.

The Jaw Epidemic: Recognition, Origins, Cures, and Prevention

Contemporary humans are living very different lives from those of their ancestors, and some of the changes have had serious consequences for health. Multiple chronic "diseases of civilization," such as cardiovascular problems, cancers, ADHD, and dementias are prevalent, increasing morbidity rates. Stress, including the disruption of traditional sleep patterns by modern lifestyles, plays a prominent role in the etiology of these diseases, including obstructive sleep apnea. Surprisingly, jaw shrinkage since the agricultural revolution, leading to an epidemic of crooked teeth, a lack of adequate space for the last molars (wisdom teeth), and constricted airways, is a major cause of sleep-related stress. Despite claims that the cause of this jaw epidemic is somehow genetic, the speed with which human jaws have changed, especially in the last few centuries, is much too fast to be evolutionary. Correlation in time and space strongly suggests the symptoms are phenotypic responses to a vast natural experiment-rapid and dramatic modifications of human physical and cultural environments. The agricultural and industrial revolutions have produced smaller jaws and less-toned muscles of the face and oropharynx, which contribute to the serious health problems mentioned above. The mechanism of change, research and clinical trials suggest, lies in orofacial posture, the way people now hold their jaws when not voluntarily moving them in speaking or eating and especially when sleeping. The critical resting oral posture has been disrupted in societies no longer hunting and gathering. Virtually all aspects of how modern people function and rest are radically different from those of our ancestors. We also briefly discuss treatment of jaw symptoms and possible clinical cures for individuals, as well as changes in society that might lead to better care and, ultimately, prevention.

Physical Activity and Sedentary Behaviour Patterns among Kenyan and Japanese Children: A Comprehensive Cross-Country Comparison

Health benefits of physical activity are well known, yet available physical activity data is limited from children living in African and Asian countries. The purpose of the cross-sectional study was to evaluate and compare physical activity and sedentary behavior patterns, particularly hourly variations, among children in Kenya and Japan. Participants included 298 primary school students (122 Kenyan, 176 Japanese) aged 9-12 years. Physical activity and sedentary behavior were measured with accelerometers. Domain-specific physical activity, screen time, and proportion of children using active transport to school were measured by questionnaire. A two-way ANOVA (countries × time) was used to examine the differences in the activity patterns between Kenyan and Japanese children. The results from the present study demonstrated that Kenyan children spent more time in moderate-to-vigorous physical activity compared to Japanese children (p < 0.05) with the greatest differences found for weekday evenings (for boys and girls) and weekend afternoons (for girls). This suggests that these were 'critical periods' to differentiate the physical activity levels between Kenyan and Japanese children. However, a higher proportion of the children from Japan used active transport to school and spent less time in television viewing and computer gaming. The results suggest that both countries have successes and challenges that can aid in developing effective and country-specific intervention strategies for promoting physical activity.

Cardiorespiratory and muscular fitness in young adult Finnish men between 2003 and 2015

INTRODUCTION

Physical fitness is strongly related to health and may offer valuable information about public health. We investigated trends in physical fitness, leisure-time physical activity (LTPA), and anthropometry of young healthy adult Finnish men in representative population-based samples between 2003 and 2015.

METHODS

Three independent cross-sectional samples of 18- to 35-year-old Finnish men were assessed in 2003 (n = 889), 2008 (n = 803), and 2015 (n = 690). Cardiorespiratory (VO₂ max) and muscular fitness (1-minute sit-ups and push-ups), body mass, and height were measured. Self-reported LTPA was assessed.

RESULTS

After adjusting for age, education, and smoking, cardiorespiratory fitness was higher in 2003 (mean: 43.5, 95%CI: 42.9-44.1 mL/kg/min) compared to 2008 (41.3, 95%CI: 40.7-41.9 mL/kg/min) and 2015 (40.6, 95%CI: 40.0-41.2 mL/kg/min) (P < .001), whereas no difference was observed between 2008 and 2015. The lowest values in muscular fitness were observed in 2003, while no clear trends were further noticed. The adjusted BMI was higher in 2008 (25.1, 95%CI: 24.9-25.4) and 2015 (25.3, 95%CI: 25.3, 95%CI: 25.0-25.6) compared to 2003 (24.5, 95%CI: 24.3-24.8) (P < .005). In 2015, a higher proportion of individuals exercised at least four times per week compared to 2003 and 2008 (P < .05).

CONCLUSION

The decrease in cardiorespiratory fitness that took place between 2003 and 2008 plateaued after 2008. The plateau is in accordance with the previously observed trend of 5-10 years younger Finnish men. Moreover, muscular fitness was for the most part higher in 2008 and 2015 compared to 2003. Efforts directed to promote regular physical activity and improve physical fitness are needed.

Moderate-to-vigorous physical activity attenuates the detrimental effects of television viewing on the cardiorespiratory fitness in Asian adolescents: the Asia-fit study

BACKGROUND

Moderate-to-vigorous physical activity (MVPA) and television viewing are independently associated with cardiorespiratory fitness. However, limited evidence is available on their combined effects, specifically of MVPA and watching television, on cardiorespiratory fitness in the young Asian population. Therefore, the present study examined whether MVPA can attenuate the detrimental effects of prolonged television viewing on the cardiorespiratory fitness of Asian adolescents.

METHODS

This is a cross-sectional study on 9553 adolescents (aged 12-15 years) from 8 Asian metropolitan cities (Tokyo, Hong Kong, Shanghai, Taipei, Bangkok, Kuala Lumpur, Seoul, and Singapore). Cardiorespiratory fitness was assessed by using a 15-m progressive aerobic capacity endurance run (PACER) test. The time spent on MVPA and watching television was assessed using the International Physical Activity Questionnaire-Short Form.

RESULTS

MVPA was more closely associated with the PACER score than the duration of watching television. Compared with the reference group (i.e. those with the lowest levels of MVPA [< 30 min/day] and the most sedentary [≥3 h/day of television time]), PACER scores were significantly higher for those who met the physical activity recommendation (≥60 min/day in MVPA), regardless of the duration of television viewing. Conversely, girls in the least active group (< 30 min/day of MVPA) who watched television < 1 h/day demonstrated better PACER scores than the reference group.

CONCLUSIONS

Sufficient MVPA (≥60 min/day) can attenuate the detrimental effects of excessive television viewing with cardiorespiratory fitness in Asian adolescents. In addition, the duration of television viewing had significant but weaker associations with cardiorespiratory fitness compared to MVPA.

Secular trends in the grip strength and body mass index of sport university students between 1973 and 2016: J-Fit＋study

Background/Objective

Sport university students are a unique population because they usually have a strong sport background since early childhood. In this study, we aimed to examine secular trends in grip strength of male, first-year sport university students in comparison with the general population between 1973 and 2016.

Methods

Existing data on the grip strength of 6,308 sport university students aged 18 years were examined. The data were obtained from the Juntendo Fitness Plus Study, a study of the Department of Physical Education/Health and Sports Science of Juntendo University. For reference, age- and sex-matched data (18 years old, male) on the grip strength were obtained from a national database.

Results

Compared with the general population, the sport university students had greater body mass index and stronger grip strength at all times.

Conclusions

The grip strength of sport university students significantly declined between the 1980s and 1990s, and it has plateaued since 2000, albeit at low levels. Compared with the peak performance of sport university students in 1984, the grip strength of students in 2016 was significantly lower by 8.1 kg. The downward trends were also confirmed in the general population during the same periods. In conclusion, the grip strength of sport university students has significantly declined over the last few decades.

Cell-Specific "Competition for Calories" Drives Asymmetric Nutrient-Energy Partitioning, Obesity, and Metabolic Diseases in Human and Non-human Animals

The mammalian body is a complex physiologic “ecosystem” in which cells compete for calories (i.e., nutrient-energy). Axiomatically, cell-types with competitive advantages acquire a greater number of consumed calories, and when possible, increase in size and/or number. Thus, it is logical and parsimonious to posit that obesity is the competitive advantages of fat-cells (adipocytes) driving a disproportionate acquisition and storage of nutrient-energy. Accordingly, we introduce two conceptual frameworks. Asymmetric Nutrient-Energy Partitioning describes the context-dependent, cell-specific competition for calories that determines the partitioning of nutrient-energy to oxidation, anabolism, and/or storage; and Effective Caloric Intake which describes the number of calories available to constrain energy-intake via the inhibition of the sensorimotor appetitive cells in the liver and brain that govern ingestive behaviors. Inherent in these frameworks is the independence and dissociation of the energetic demands of metabolism and the neuro-muscular pathways that initiate ingestive behaviors and energy intake. As we demonstrate, if the sensorimotor cells suffer relative caloric deprivation via asymmetric competition from other cell-types (e.g., skeletal muscle- or fat-cells), energy-intake is increased to compensate for both real and merely apparent deficits in energy-homeostasis (i.e., true and false signals, respectively). Thus, we posit that the chronic positive energy balance (i.e., over-nutrition) that leads to obesity and metabolic diseases is engendered by apparent deficits (i.e., false signals) driven by the asymmetric inter-cellular competition for calories and concomitant differential partitioning of nutrient-energy to storage. These frameworks, in concert with our previous theoretic work, the Maternal Resources Hypothesis, provide a parsimonious and rigorous explanation for the rapid rise in the global prevalence of increased body and fat mass, and associated metabolic dysfunctions in humans and other mammals inclusive of companion, domesticated, laboratory, and feral animals.

Anthropometric measures as fitness indicators in primary school children: The Health Oriented Pedagogical Project (HOPP)

Aims: As children’s fitness continues to decline, frequent and systematic monitoring of fitness is important. Easy-to-use and low-cost methods with acceptable accuracy are essential in screening situations. This study aimed to investigate how the measurements of body mass index (BMI), waist circumference (WC) and waist-to-height ratio (WHtR) relate to selected measurements of fitness in children. Methods: A total of 1731 children from grades 1 to 6 were selected who had a complete set of height, body mass, running performance, handgrip strength and muscle mass measurements. A composite fitness score was established from the sum of sex- and age-specific z-scores for the variables running performance, handgrip strength and muscle mass. This fitness z-score was compared to z-scores and quartiles of BMI, WC and WHtR using analysis of variance, linear regression and receiver operator characteristic analysis. Results: The regression analysis showed that z-scores for BMI, WC and WHtR all were linearly related to the composite fitness score, with WHtR having the highest R2 at 0.80. The correct classification of fit and unfit was relatively high for all three measurements. WHtR had the best prediction of fitness of the three with an area under the curve of 0.92 ( p < 0.001). Conclusions: BMI, WC and WHtR were all found to be feasible measurements, but WHtR had a higher precision in its classification into fit and unfit in this population.

Longitudinal Changes in Physical Activity Level, Body Mass Index, and Oxygen Uptake Among Norwegian Adolescents

Several studies have investigated activity levels among adolescents, but no study has examined longitudinal changes in physical activity (PA) level, body mass, and oxygen uptake among the same adolescents from the age of 14 to 19 years. The present study examined data from a research project that included a group of randomly selected students (N = 116) with objective measurements of PA (accelerometer data), self-reported PA level, and body mass and oxygen uptake during a 5-year period. The results show a significant decrease in the accelerometer-based PA level over time, from age 14 to 19. At 14 years of age, the minutes of moderate and/or vigorous PA was 66.7 min·day^-1, but was less than half, at only 24.4 min·day^-1, at 19 years of age. The self-reported activity data show a decrease in girls' general activity level over time, while boys' activity level during school breaks decreased strongly during the period: at age 14, 61% of the boys were classified as active, while at age 19, only 11% were physically active. Furthermore, body mass index increased during the period for both genders, while oxygen uptake decreased. Since both BMI and maximal oxygen uptake are important risk factors for future CVD, these findings point toward the importance of maintaining a high activity level during childhood and adolescence, in order to keep fit later in life.

Secular Trends in the Physical Fitness of United States Army Recruits on Entry to Service, 1975-2013

Knapik, JJ, Sharp, MA, and Steelman, RA. Secular trends in the physical fitness of United States Army recruits on entry to service, 1975-2013. J Strength Cond Res 31(7): 2030-2052, 2017-A systematic literature search was conducted to identify and analyze articles that reported on physical fitness of new US Army recruits. The National Library of Medicine's PubMed and the Defense Technical Information Center were searched using the keywords (military personnel OR trainee OR recruit OR soldier) AND (physical fitness OR strength OR endurance OR flexibility OR balance OR coordination OR muscle contraction OR running OR exercise OR physical conditioning). Reference lists of obtained articles and contact with authors enhanced the search. Studies were selected if they involved recruits in Basic Combat Training or One-Station Unit Training, provided a quantitative assessment of at least one fitness measure, and the fitness measure(s) were obtained early in training. Average values for each fitness measure were obtained, plotted by the year of data collection, and fitted to linear regression models (fitness measure × year). Fifty-three articles met the review criteria. Regression analysis indicated little temporal change in height, but body weight, body mass index, body fat, and fat-free mass increased over time. Limited V[Combining Dot Above]O2max data suggested no temporal change in male recruits, but those in female recruits V[Combining Dot Above]O2max seem to have slightly improved. Apparently contradicting the V[Combining Dot Above]O2max findings, performance on endurance runs (1- and 2-mile) declined, possibly because of the increase in body weight. Muscular endurance (push-ups, sit-ups) demonstrated little systematic change over time. Limited but multiple measures of muscular strength suggest a temporal increase in strength. Specific components of US Army recruit fitness seem to have changed over time.

Temporal trends in the cardiorespiratory fitness of children and adolescents representing 19 high-income and upper middle-income countries between 1981 and 2014

OBJECTIVE

To estimate international and national temporal trends in the cardiorespiratory fitness (CRF) of children and adolescents and to examine relationships between temporal trends in CRF and temporal trends in broad socioeconomic and health-related indicators across countries.

METHODS

Data were obtained from a systematic search of studies that explicitly reported 20 m shuttle run test (a validated measure of CRF) descriptive data on apparently healthy individuals aged 9-17 years. Following the estimation of relative peak oxygen uptake (mL/kg/min) as a measure of CRF, sample-weighted temporal trends were estimated at the country-sex-age level using best-fitting linear or polynomial regression models relating the year of testing to mean CRF. Poststratified population-weighted mean changes in absolute and per cent CRF were estimated. Pearson's correlations were used to describe the association between linear temporal trends in CRF and linear temporal trends in broad socioeconomic and health-related indicators.

RESULTS

Temporal trends were estimated from 965 264 children and adolescents from 19 high-income and upper middle-income countries between 1981 and 2014, using data from 137 studies. Collectively, there was a moderate decline in CRF of 3.3 mL/kg/min (95% CI -3.5 to -3.1), equivalent to a decline of 7.3% (95% CI -7.8% to -6.7%) over the 33-year time period. This international decline diminished with each decade and stabilised near zero around 2000. The decline was larger for boys than girls and was similar for children and adolescents. Trends also differed in magnitude and direction between countries, with most showing declines. There was a strong negative association between country-specific trends in income inequality (Gini index) and trends in CRF across 18 countries; meaning, countries approaching income equality had more favourable trends in CRF.

CONCLUSIONS

There has been a substantial decline in CRF since 1981, which is suggestive of a meaningful decline in population health. However, the international trend in CRF has not followed the anticipated trajectory, diminishing and stabilising with negligible change since 2000. CRF data are needed from children in low-income and middle-income countries to more confidently determine true international trends and determine whether temporal trends are similar to those observed in high-income and upper middle-income countries.

Are We Reaching the Limits of Homo sapiens?

Echoing scientific and industrial progress, the Twentieth century was an unprecedented period of improvement for human capabilities and performances, with a significant increase in lifespan, adult height, and maximal physiological performance. Analyses of historical data show a major slow down occurring in the most recent years. This triggered large and passionate debates in the academic scene within multiple disciplines; as such an observation could be interpreted as our upper biological limits. Such a new phase of human history may be related to structural and functional limits determined by long term evolutionary constraints, and the interaction between complex systems and their environment. In this interdisciplinary approach, we call into question the validity of subsequent forecasts and projections through innovative and related biomarkers such as sport, lifespan, and height indicators. We set a theoretical framework based on biological and environmental relevance rather than using a typical single-variable forecasting approach. As demonstrated within the article, these new views will have major social, economical, and political implications.

Can Policy Alone Stop Decline of Children and Youth Fitness?

Various models and methods have been proposed to address the worldwide decline in children's and youth's physical fitness, and the social-ecological model has shown some promise. Yet, the impact of the policy intervention, 1 component of that model, has not been evaluated carefully. Using limited data from policy documents, the impact of policy related to children and youth fitness in China was examined, and it was found that the policy alone did not seem to work. Possible reasons are explored, and a call for more policy evaluation research is made.

The Validity of US Nutritional Surveillance: USDA's Loss-Adjusted Food Availability Data Series 1971-2010

The purpose of this study was to examine the validity of the 1971-2010 United States Department of Agriculture's (USDA's) loss-adjusted food availability (LAFA) per capita caloric consumption estimates. Estimated total daily energy expenditure (TEE) was calculated for nationally representative samples of US adults, 20-74 years, using the Institute of Medicine's predictive equations with "low-active" (TEE L-ACT) and "sedentary" (TEE SED) physical activity values. TEE estimates were subtracted from LAFA estimates to create disparity values (kcal/d). A validated mathematical model was applied to calculate expected weight change in reference individuals resulting from the disparity. From 1971-2010, the disparity between LAFA and TEE L-ACT varied by 394kcal/d-(P < 0.001), from -205kcal/d (95% CI: -214, -196) to +189kcal/d (95% CI: 168, 209). The disparity between LAFA and TEE SED varied by 412kcal/d (P < 0.001), from -84kcal/d (95% CI: -93, -76) to +328kcal/d (95% CI: 309, 348). Our model suggests that if LAFA estimates were actually consumed, reference individuals would have lost ~1-4kg/y from 1971-1980 (an accumulated loss of ~12 to ~36kg), and gained ~3-7kg/y from 1988-2010 (an accumulated gain of ~42 to ~98kg). These estimates differed from the actual measured increments of 10kg and 9kg in reference men and women, respectively, over the 39-year period. The USDA LAFA data provided inconsistent, divergent estimates of per capita caloric consumption over its 39-year history. The large, variable misestimation suggests that the USDA LAFA per capita caloric intake estimates lack validity and should not be used to inform public policy.

International normative 20 m shuttle run values from 1 142 026 children and youth representing 50 countries

OBJECTIVE

To develop sex-specific and age-specific international norms for the 20 m shuttle run test (20mSRT) in children and youth (aged 9-17 years), and to estimate the prevalence meeting the FITNESSGRAM criterion-referenced standards for healthy cardiorespiratory endurance (CRE).

METHODS

A systematic review was undertaken to identify papers explicitly reporting descriptive 20mSRT (with 1 min stages) data on children and youth since 1981. Data were included on apparently healthy (free from known disease/injury) 9-17 years old. Following standardisation to a common metric and for protocol differences, pseudo data were generated using Monte Carlo simulation, with population-weighted sex-specific and age-specific normative centiles generated using the Lambda Mu and Sigma (LMS) method. Sex-related and age-related differences were expressed as per cent and standardised differences in means. The prevalence with healthy CRE was estimated using the sex-specific and age-specific FITNESSGRAM criterion-referenced standards for [Formula: see text].

RESULTS

Norms were displayed as tabulated centiles and as smoothed centile curves for the 20mSRT using 4 common metrics (speed at the last completed stage, completed stages/minutes, laps and relative [Formula: see text]). The final data set included 1 142 026 children and youth from 50 countries, extracted from 177 studies. Boys consistently outperformed girls at each age group (mean difference±95% CI: 0.86±0.28 km/h or 0.79±0.20 standardised units), with the magnitude of age-related increase larger for boys than for girls. A higher proportion of boys (mean±95% CI: 67±14%) had healthy CRE than girls (mean±95% CI: 54±17%), with the prevalence of healthy CRE decreasing systematically with age.

CONCLUSIONS

This study provides the most comprehensive and up-to-date set of international sex-specific and age-specific 20mSRT norms for children and youth, which have utility for health and fitness screening, profiling, monitoring and surveillance.