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Trends in physical fitness, growth, and nutritional status of Chinese children and adolescents: a retrospective analysis of 1·5 million students from six successive national surveys between 1985 and 2014

https://doi.org/10.1016/S2352-4642(19)30302-5Get rights and content

Summary

Background

Physical fitness is strongly associated with health. Despite the extent of the nutritional transition from food scarcity to diets high in fats and refined carbohydrates that has occurred in China, to our knowledge, trends in physical fitness have not been described. We aimed to assess trends in physical fitness and its association with the nutritional transition among Chinese children and adolescents.

Methods

In this retrospective analysis, data from Chinese school students aged 7–18 years were extracted from six successive national surveys undertaken between 1985 and 2014. Six components of physical fitness (forced vital capacity, standing long jump, sit-and-reach, body muscle strength, 50 m dash, and endurance running) were measured repeatedly in each survey and aggregated as a summary physical fitness indicator (PFI). Growth and nutritional status (stunting, thinness, normal weight, overweight, and obesity) were defined by use of WHO definitions, and we combined stunting and thinness as undernutrition and overweight and obesity as overnutrition. Urbanisation levels were obtained from the statistical yearbook of the National and Provincial Bureau of Statistics of China. We used fractional polynomial regression and generalised additive models to assess associations between PFI and nutritional outcomes and between PFI and levels of urbanisation.

Findings

Between 1985 and 2014, 1 513 435 students participated in the Chinese National Survey on Students' Constitution and Health, and 1 494 485 were included in our study. We observed a decline of the PFI during 1985–2014 (overall PFI change −0·8), albeit with an increase from 1985 to 1995 (PFI change 1·2), coinciding with a shift in the major nutritional problems from stunting and thinness to overweight and obesity. Both undernourished (PFI −2·44 for thin and −3·42 for stunting) and overnourished (–1·49 for overweight and −3·63 for obese) students had a lower PFI than that of those with normal weight (–0·41) in 2014. Boys had a larger decline in PFI than girls in 1985–2014, especially boys with obesity (PFI change −2·7). We observed the highest PFI in 1995 (1·17), when the proportion of students with normal weight was highest. Advancing urbanisation was accompanied by declines in physical fitness, which occurred in both students in rural settings and those in urban settings in these regions.

Interpretation

Our study supports the continuation of policies to improve physical fitness that focus on undernutrition, including economic subsidies, in poorer rural regions. However, for most of China, taxation of unhealthy foods, promotion of physical activity, reduction in academic pressures, promotion of dietary diversity, reduction of sedentary time, and engagement in formal sporting activities should be elements of policies to promote healthy weight status and prevent obesity in school students, which will also support physical fitness.

Funding

National Natural Science Foundation, Humanities and Social Sciences Planning Fund Project, China Scholarship Council, and Innovation Fund for Outstanding Doctoral Candidates of Peking University Health Science Center.

Introduction

Physical fitness, the ability to do activities or motions effectively and efficiently, is widely considered to be an important component of health because of its links with a range of non-communicable diseases.1 Lower levels of physical fitness are associated with several health problems, including higher risks of later-life cardiovascular disease, hypertension, diabetes, cancer, and mental disorders across all ages.2, 3, 4 The 2018 Physical Activity Guidelines for Americans indicated that regular physical activity and good physical fitness could improve bone health, weight status, cardiorespiratory and muscular fitness, cardiometabolic health, and cognition and reduce risks of depression in children and adolescents.5 Peak physical fitness typically occurs in adolescence, with strong continuities into later life; therefore, the fitness levels of a country's children and adolescents are likely to provide insight into the future health profile of that country's adult population.6, 7 Previous studies have shown a worldwide decline in aerobic performance in children since the late 1950s,8 and a particularly marked decline in the maximal long-distance running performance of Asian children and adolescents, including those from China.9

Research in context

Evidence before this study

China has undergone a rapid nutritional transition in the past few decades, bringing remarkable reductions in stunting and underweight in children, but sharp increases in overweight and obesity. To our knowledge, the overall effect of these substantial changes in growth and nutritional status on the physical fitness of Chinese children and adolescents has not been comprehensively assessed. We searched PubMed, China National Knowledge Infrastructure, and Wanfang on July 14, 2019, using the terms “physical fitness” AND (“nutritional status” OR “nutritional problems” OR “nutritional burdens”) OR (“stunting” AND “thinness” AND “overweight and obesity”) AND “trends” AND “children and adolescents” AND “China” for articles published in English and Chinese, without date restrictions. Our search found some relevant studies, but no comprehensive reports of changing patterns of physical fitness and nutritional status in children and adolescents either in China or elsewhere. In this context, the nationally representative Chinese National Survey on Students' Constitution and Health provided a unique opportunity to analyse trends in child and adolescent physical fitness over 30 years and their association with growth and nutritional status.

Added value of this study

To our knowledge, this is the first study to comprehensively assess trends in physical fitness and their association with nutritional transition in children and adolescents in China. From 1985 to 2014, 1 494 485 Chinese students were included in these analyses of physical fitness using a summary indicator that combined six components of physical fitness (forced vital capacity, standing long jump, sit-and-reach, body muscle strength, 50 m dash, and endurance running). Children and adolescents at both extremes of growth and weight ranges had poorer physical fitness than those with normal weight and height. We observed a comprehensive decline in physical fitness from 1995 to 2014, particularly in boys with obesity. Physical fitness of children and adolescents improved more in areas with lower levels of urbanisation, largely driven by reductions in undernutrition. However, rapid urbanisation was associated with increases in overweight and obesity and an overall decline in physical fitness.

Implications of all the available evidence

30 years of rapid economic development in China have been accompanied by a decline in the physical fitness of children and adolescents, including respiratory function, strength, explosive power, and cardiorespiratory endurance. Government policies should refocus away from underweight status to the maintenance of a normal weight and prevention of obesity. Advancing urbanisation seems to be a useful indicator of the need to adopt strategies to promote healthy and diverse diets, maintain physical activity, and reduce sedentary time.

The definition of physical fitness has evolved to include both metabolic and morphological components, and it commonly consists of four elements: muscular strength, muscular endurance, cardiorespiratory endurance, and motor ability.7 Although differences in measures of physical fitness exist, core items typically include endurance running (reflecting cardiopulmonary function),10 standing long jump, 1-min pull-ups and sit-ups (reflecting body muscle strength),11 sit-and-reach (reflecting hamstring and lower back flexibility),12 forced vital capacity (FVC; reflecting respiratory function),13 and the 50-m (or 60-m) dash (reflecting explosive force and speed). Therefore, physical fitness measurement integrates the different functions and structures that are activated during exercise, including musculoskeletal, cardiorespiratory, haemato-circulatory, endocrine-metabolic, and psychoneurological functions.14 Combining the core items into a summary physical fitness indicator (PFI)15, 16 allows the assessment of physical fitness at both individual and population levels.

Concerns about lower physical fitness and greater physical inactivity in children and adolescents have been raised in some areas of China. Changing patterns of weight might be one contributor to this change, given the association of obesity with poor physical fitness and cardiovascular risk.17, 18 In adults, a reverse U-shaped relationship between body-mass index (BMI) and physical fitness seems to exist, but this has been less explored in children.16 Upward shifts in BMI might become a major contributor to poor physical fitness in children and adolescents, even though undernutrition remains the major nutritional problem globally.19 In addition to the effects of a rapid nutrition transition, urbanisation is another potential contributor to low physical fitness, not only through increasing risks for obesity, but also through diminishing opportunities for physical activity.20

No previous study has comprehensively assessed trends in physical fitness among Chinese children and adolescents nor examined the effects of the nutrition transition and urbanisation. For these reasons, we aimed to assess secular trends in the physical fitness of Chinese students, including cardiovascular fitness, muscular strength, muscular endurance, speed, power, and flexibility from 1985 to 2014; assess the association between physical fitness and growth and nutritional status; and explore the effects of urbanisation on physical fitness in Chinese students.

Section snippets

Study design and participants

For this retrospective analysis, data were extracted from successive cycles (1985, 1995, 2000, 2005, 2010, and 2014) of the Chinese National Survey on Students' Constitution and Health (CNSSCH). The CNSSCH are the largest nationally representative surveys of the health status of Chinese children and adolescents aged 7–18 years. The CNSSCH uses a multistage stratified cluster sampling design and has maintained consistent approaches to sampling and assessment across the different survey years, as

Results

Between 1985 and 2014, 1 513 435 children and adolescents participated in the CNSSCH. 18 950 participants (1·27%) were not eligible for participation in the study, resulting in 1 494 485 participants with complete records on age, sex, height, weight, and physical fitness measurements who were included in the final analysis (table; appendix 2, p 4). The proportions of the study population across urban and rural areas and by sex and age groups were consistent across the different survey years. In

Discussion

In our study, we observed that physical fitness in Chinese students peaked in 1995, at a point when the proportion of those with a normal weight status was highest. Since then, a substantial decline has occurred in the physical fitness of children and adolescents, with overall fitness being 167% lower in 2014 than in 1995. We found evidence of an inverse U-shape association between physical fitness and growth and nutritional status, with students with stunting or thin status and overnourished

Data sharing

All the data (de-identified) collected in the surveillance system can be shared with investigators, whose proposed use of the data has been approved by an independent review committee identified for this purpose, by contacting the corresponding author. The study protocol and statistical analysis plan must be approved by the committee. Proposals should be directed to [email protected] and [email protected].

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