Comparison of physical activity, sedentary time, and physical fitness among Chinese children and adolescents in Qinghai between 2019 and 2023
This study mainly investigated the differences in physical activity and physical fitness between results from 2019 and those from 2023 using a cross-sectional comparison. Results showed a significant overall increase in MVPA and a significant decrease in SED in 2023 compared to 2019, suggesting a shift toward more active lifestyles, potentially driven by policy interventions, school activity programmes, and heightened public health awareness. Endurance, strength, flexibility, coordination and speed show different changes in different classes compared to 2019. We also investigated the association of MVPA and SED with physical fitness, and mixed associations were found in this population. Further studies are needed to better understand the association of MVPA and SED with physical fitness in children and adolescents in Qinghai Province.
For endurance, vital capacity improved significantly at all school stages. Primary school girls showed improved performance in the 50 × 8 shuttles run, while secondary school students experienced significant declines in the 800 m and 1000 m runs. Strength tests revealed improvements in the standing long jump among middle and high school students but declines in pull-ups for high school boys. Timed sit-ups declined for middle school girls, with no significant changes at primary and high school. Flexibility improved for high school boys and both middle and high school girls but decreased for primary school boys and girls, as well as for middle school boys. Coordination, measured only in primary schools through the timed rope-skipping test, improved significantly compared to 2019. In speed, primary school students improved significantly in the 50 m dash, whereas middle and high school students demonstrated significant declines.
The regression analysis results have shown that MVPA was positively associated with vital capacity, standing long jump, timed sit-ups, pull-ups, and 800 m running performance, while negatively associated with 1000 m running performance, timed rope-skipping, and 50 m dash. SED showed positive associations with 800 m and 1000 m running performance, reflecting a greater running time, and was positively associated with timed sit-ups. No significant associations were found in other variables.
These findings highlight the differing trends of physical fitness development across academic stages. The observed trends may be influenced by physiological changes during puberty, academic stress, and environmental conditions like high altitude. Future research should focus on understanding the specific needs of students at different stages of education, providing a robust theoretical and applied foundation for developing scientific and effective health promotion strategies.
Compared to 2019, the overall MVPA of children and adolescents in 2023 shows a significant increase, and SED shows a significant decrease30. These changes may be attributed to national policies, school initiatives promoting physical activity, and growing societal and parental attention to adolescent health. The Chinese government’s “Healthy China 2030” strategy has actively encouraged adolescents to engage in at least one hour of daily physical activity. Furthermore, diversifying physical education curricula and increased outdoor activities in recent years likely contributed to greater sports participation31.
However, MVPA decreased among girls in middle and high schools, potentially due to increased academic pressure. At these stages, students often allocate more time to exam preparation and supplementary classes, reducing opportunities for physical activity32. Additionally, physiological and psychological factors, such as body weight changes or social perceptions of physical activity, may lower high school girls’ willingness to exercise vigorously after puberty. The reduction in SED was significant across all academic stages, possibly due to widespread social awareness of the dangers of sedentary behaviour and measures taken by families to reduce time spent on electronic devices30. Most schools encouraged the reduction of SED through structured physical activities during breaks, such as organised sports or active breaks. This trend towards reducing sedentary time has helped to improve students’ cardiorespiratory health and neuromuscular function.
Endurance in children and adolescents is mainly assessed by vital capacity, the 50 m × 8 shuttles run in primary school and the 800/1000 m run in secondary school. Relative to 2019, vital capacity was significantly higher for both sexes in all school years in 2023. It has been shown that the low-oxygen environment at high altitudes enhances respiratory muscle strength and blood oxygen-carrying capacity, which manifests itself as a gradual adaptive improvement in lung function16,33. Additionally, an increase in MVPA and a decrease in SED may also contribute, to a certain extent, to the enhancement of vital capacity. The regression analysis further indicated a significant positive association between MVPA and vital capacity, suggesting that higher physical activity levels contribute to improved respiratory function. Previous studies have shown that MVPA positively affects vital capacity and can improve lung function34. Regular and vigorous breathing during exercise will increase the capacity of the respiratory muscles35. However, the regression analysis did not show a significant association between SED and vital capacity in this study, suggesting that other factors, such as environmental or developmental influences, might play a more dominant role. While the direct association between SED and vital capacity was not evident in this study, prolonged sedentary behaviour is widely recognised in health. Prolonged sedentary behaviour is known to trigger several chronic diseases, including cardiovascular disease and impaired lung function36. Some studies have shown that increased sedentary time can cause fat to accumulate around the ribs, abdomen, and diaphragm. Too much fat can affect ventilation dynamics, reducing lung function37,38.
The long-distance running endurance test showed a marked difference in performance between the different academic stages. In 2023, the 50 m × 8 shuttles run of primary school girls improved compared to 2019, suggesting better endurance in short-duration, high-intensity interval running. This improvement may be partially related to the significant increase in MVPA among primary school-aged students. However, the regression analysis did not show significant associations between the 50 m × 8 shuttles run and MVPA or SED, which may be because primary school girls have not yet experienced the physiological changes of puberty, such as increased body fat, which has less negative effect on endurance quality. However, the decreasing trend in endurance at the secondary school, with 800 m running for high school girls and 1000 m running for middle school boys, was significantly lower in 2023. Linear regression results showed that MVPA was positively associated with 800 m running in girls but negatively associated with 1000 m running in boys, while SED was positively associated with both endurance indicators. This suggests that increasing MVPA and reducing SED may benefit endurance, particularly in boys. However, despite these positive associations, endurance performance continued to decline, indicating the influence of additional factors. The hypoxic environment at high altitudes exerts a more significant physiological burden on the cardiorespiratory systems of children and adolescents39, which may be particularly evident in endurance events such as long-distance running.
The pull-ups, standing long jump, and timed sit-ups tests reflect upper-body, lower-body, and core strength in children and adolescents. In terms of lower limb strength, this study found improvements in standing long jump performance in both middle and high school girls and middle school boys. Although middle and high school girls experienced a reduction in MVPA, their standing long jump performance still improved, which could be due to the decrease in SED. Reducing SED may help to maintain or improve lower limb strength because reduced sedentary time can activate muscles and improve muscle activity and neuromuscular coordination, thereby maintaining or improving athletic performance. This improvement in neuromuscular function was significantly enhanced after a prolonged reduction in sedentary behaviour40. In middle school boys, the increase in MVPA contributed significantly to the improvement in lower limb strength. Research has shown that MVPA significantly affects the activation of fast-twitch muscle fibres, which are critical for explosive movements such as the standing long jump41. Compared to girls, boys are generally more likely to participate in activities associated with strength and explosiveness, such as football, which helps to improve the explosive power of their lower limb muscles42. Furthermore, reducing SED not only helps maintain muscle strength but also improves the functionality of the neuromuscular system, leading to improved coordination and performance during physical activity43.
In our study, the pull-ups performance of high school boys decreased significantly compared to 2019. Although MVPA increased in 2023 compared to 2019, the upper body strength qualities of the boys showed no significant improvement. Research has shown that as adolescents gain weight, the strength required to complete a pull-up increases and that weight gain negatively affects pull-up performance22. Meanwhile, inadequate targeted strength training was another critical factor. Failure to regularly train specific upper body muscles, particularly the back and arm muscles, led to decreased pull-up performance in boys44,45. Additionally, muscle atrophy resulting from diminished bone strength may occur at elevated altitudes, harming the maintenance of upper limb muscle strength.
Furthermore, significant differences in core strength between girls in different school years were observed. Specifically, the timed sit-ups performance of middle school girls decreased significantly in 2023, whereas there was no significant change in the performance of primary and high school girls. This phenomenon may be related to MVPA changes and SED. The study results showed that MVPA decreased among middle and high school girls and increased among primary school girls in 2023, which may explain the differences in core strength performance between girls of different academic stages. It has been suggested that MVPA plays a crucial role in maintaining and developing strength in the core muscle groups and that a decrease in MVPA may lead to a deterioration in core strength46,47.
We found that high school boys and middle and high school girls showed significant improvements in sit-and-reach on the flexibility test compared to 2019, despite regression analysis not showing significant associations between MVPA, SED and flexibility. These findings may reflect broader lifestyle or developmental changes. Previous studies show that increased MVPA contributes to enhanced muscle extension and joint flexibility, whereas reduced sedentary time contributes to enhanced flexibility by assisting in maintaining joint and muscle function48,49. Improved flexibility in middle and high school girls may be closely linked to physiological changes during puberty, as studies indicate that flexibility typically begins to improve significantly around the age of 11 due to puberty-related developments50. As the body develops, joint flexibility and muscle elasticity increase, and girls are able to perform well in flexibility tests even when MVPA decreases. In addition, genetic factors may also have a potential influence on flexibility, and most girls are born with better flexibility, providing a physiological basis for their improved flexibility51. Prolonged sedentary behaviour has been shown to lead to the functional deterioration of joints and muscles, while reducing sedentary time promotes joint and muscle health and increases flexibility52. These findings suggest that flexibility development may be influenced by physiological, behavioural, and genetic factors.
In contrast, there was a significant decrease in the flexibility performance of primary and middle school boys and primary school girls compared to 2019. Despite a significant increase in MVPA and a significant decrease in SED, primary and middle school boys did not show a concomitant improvement in flexibility but instead showed a decreasing trend. This finding indicates that the impact of changes in MVPA and SED on flexibility may be constrained by physiological factors associated with growth and developmental processes. It has been suggested that adolescents typically experience rapid skeletal growth and development during pre-puberty, and this change may temporarily limit muscle extensibility and joint range of motion53. Furthermore, the reduction in flexibility performance among primary schoolgirls may be associated with the type of exercise employed for MVPA. Despite an increase in MVPA, these activities did not improve flexibility. The enhancement of flexibility typically necessitates the implementation of targeted training regimens, such as stretching and yoga. It is unlikely that general physical activity alone will prove an efficacious means of improving flexibility54. Therefore, despite an increase in overall physical activity, the absence of targeted flexibility training may be the primary factor contributing to the observed decline in flexibility among primary school girls.
In our analysis of the timed rope-skipping of primary school boys and girls, we found that the timed rope-skipping performance of both sexes improved significantly in 2023 compared to 2019. As a high-intensity explosive exercise, rope skipping not only reflects the explosive power of the lower limbs but also requires coordination of the whole body, especially when performing multiple jumps in a short period, precise rhythmic control of the whole body is crucial55. For boys, despite a significant increase in MVPA, regression analysis revealed a negative association between MVPA and rope-skipping performance. This may be explained by short-term muscle fatigue caused by high-intensity physical activity, which temporarily impairs neuromuscular coordination56. While increased MVPA likely enhances overall physical fitness, including cardiorespiratory fitness and muscular explosive power, it may not directly translate to improved performance in tasks demanding high levels of neuromuscular coordination, such as rope skipping. However, the performance of girls in the timed rope-skipping test showed an enhancement. This discrepancy may be attributed to sex-specific activity preferences, with girls demonstrating a stronger inclination towards coordination-focused activities such as yoga and skipping, which are known to promote rhythm and whole-body coordination57.
This study showed a significant increase in 50 m dash for both boys and girls in primary school in 2023 compared to 2019, while there was a decrease in performance for both boys and girls in middle and high school. MVPA has been shown to improve muscle strength and explosiveness, which in turn improves sprinting ability in the short term58. This can have a positive effect on the speed of children and adolescents. Reducing SED also improves lower limb explosiveness, which positively affects speed41. However, middle and high school students show a significant decline in 50 m dash performance in 2023 compared to 2019. Adolescence is a critical period in which individuals rapidly gain weight and height; this physiological change can negatively affect speed qualities. Adolescent boys and girls gain weight, and, in particular, the percentage of body fat increases, which can affect the performance of fast sprinting ability59. In addition, as the academic load increases, particularly in middle and high school, students spend relatively less time in physical activity, especially in the absence of high-intensity training specifically targeting speed, which may further contribute to the decline in speed qualities60. Therefore, despite improvements in MVPA and SED, which contribute to students’ overall health, specific training targeting speed skills remains inadequate, with implications for improving sports performance.
There were several strengths to this study. First, this study has a large sample size, with data collected from 5,039 students in 2019 and 8,257 students in 2023, respectively, covering a wide range of primary to high school years. Such a large sample size provides high statistical validity and strong representativeness for the results of this study. Second, by comparing the data at the two time points of 2019 and 2023, this study reveals the trend of changes in physical fitness and health across different school segments and sexes, and this longitudinal comparison provides a solid basis for policy formulation and evaluation of interventions.
Several limitations of our study should be considered. First, the participants in this study in 2019 differed from those in 2023. Thus, this was a cross-sectional study that could not definitively infer the causal effects of MVPA and SED on physical fitness. Future cohort studies might better show the long-term impact of MVPA and SED on physical fitness. Second, other potential variables, such as family socio-economic status and dietary habits, which could potentially influence the results, were not adequately controlled for. Third, the sample in this study was only from Qinghai province, which may limit the applicability of the findings to other regions. Future studies could improve the generalisability and explanatory power of the results by integrating data from more regions while controlling for potential confounders such as socioeconomic status and dietary habits. Fourth, while our study focused on MVPA and SED, it did not encompass a more comprehensive 24-hour movement behaviour framework, which includes LPA and sleep. Research has shown that the interactions between MVPA, SED, LPA, and sleep can provide deeper insights into health outcomes. Future studies should adopt longitudinal designs to examine these interactions and explore their broader health, psychological, and environmental implications. Therefore, future studies should focus on these aspects to make the study more comprehensive and reliable.
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