Changes in modern lifestyle have led to a pronounced decrease in human physical activity (hereafter, physical activity). Numerous studies have demonstrated that the decreased amount of physical activity among students is the most important reason for the decline in physical fitness. Moreover, physical inactivity among students has become a global health problem. To promote health, the World Health Organization (WHO) has recommended that children and adolescents (aged 5–17 years) engage in 60 min of moderate- to vigorous-intensity physical activity (MVPA) (1). Studies on international instrumental measurements of MVPA in children have illustrated that no more than 45% of students meet the daily recommendations of the WHO (2, 3), where only 8% of adolescents meet the standard (1). In Finland, 90% of girls and 77% of boys have not met the daily recommended amount (MVPA ≥ 60 min/day) in a self-report (4). In several European countries, accelerometer measurements of children aged 10–12 years indicated that only 4.6% of girls as well as 16.8% of boys met the recommended amount (5).

In China, the current state of physical activity among students is also worrisome. According to the data of the 2010 National Physical Fitness and Health Test on the physical activity levels (PALs) of 166,812 school children aged 9–18 years in 30 provinces in China, only 22.7% of the students reported having achieved the recommended 60 min of physical activity per day (6). Moreover, data by age group demonstrated that 32.7%, 20.7%, and 12.5% of students aged 9–13, 13–16, and 16–19 years, respectively, achieved the recommended amount of physical activity. The data have reflected a trend of decreasing PALs among students with the increase in age. Wang (7) used an accelerometer to test the daily physical activity of 2,897 children and adolescents in 11 cities in China and determined their levels of physical activity from ages 9 to 17 years. Specifically, only 5.6% of the students met the WHO recommendation (MVPA ≥ 60 min/day), and, in particular, only 1.9% of the group of female students met the standard requirement. In addition to the insufficient time for engaging in MVPA, the Chinese students displayed increased sedentary hours. Dearth-Wesley et al. (8) conducted a longitudinal study and demonstrated that the proportion of students with more than 2 h of daily sedentary time during leisure time reached 58.9%.

Inadequate physical activity is strongly associated with health in students. Wu et al. (9) found that high levels of physical activity were associated with better health-related quality of life after a systematic review of 31 papers. Moreover, increased time spent on SB was associated with low quality of life in children and adolescents. The dose–response relationship among physical activity, SB, and health-related quality of life suggested that high frequencies of physical activity or less time spent on SB is associated with better health-related quality of life. For this reason, China proposed an MVPA of no less than 60 min/day for students to promote their health (10). Scholars demonstrated that regular physical activity provided many health benefits for children and adolescents such as weight loss (11). In addition, health benefits gained during childhood and adolescence can persist into later life; for example, children with high levels of physical activity early in life exhibit high levels of bone mass density in later childhood (12). A 21-year follow-up survey illustrated that groups of children and adolescents with long-term physical activity obtained low risks of developing metabolic syndrome in adulthood (13). In addition, the development of exercise habits in children and adolescents is particularly important. Previous studies indicated that children and adolescents with low levels of physical activity also have low levels of physical activity in adulthood (14, 15). Thus, the urgent need emerged to effectively curb the prevalence of physical inactivity among students and to improve levels of physical activity. Alternatively, physical inactivity limits the improvement of the physical health of students, and an increasing number of evidence-based reports due to the increased research on physical activity supported the health-promoting function of physical activity (16).

Given the health benefits of regular physical activity, we might wonder why students are not active at recommended levels. There are many common barriers that affect students' physical activity. There are many common barriers to physical activity, such as lack of time, lack of social support, lack of energy, lack of motivation, fear of injury, lack of skill, lack of facilities, and weather conditions (17). Understanding common barriers to physical activity and developing strategies to overcome them may help students make physical activity a part of their daily lives.

Physical activity among students is not a simple isolated behavior; a combination of physiological, psychological, and social factors determines the behavior of participating and sustaining physical activity, and the complexity of such a behavior determines the diversity and relevance of intervention strategies. The social–ecological model proposed by Bronfenbrenner in 1977 (18) is a widely used and comprehensive theoretical framework for analyzing the factors that influence physical activity and guide the design of intervention strategies and programs. The model emphasizes that a combination of individual and environmental factors, including those at the individual (attitudes, cognition, and self-efficacy), interpersonal (social support and role models), organizational (factors related to the major places of daily activity, e.g., schools and families), community (physical environment and staffing), and policy (national or local health promotion policies and resources) levels. Thus, the factors that influence physical activity are multi-dimensional.

In this regard, the multidimensional and interacting changes in the various influencing factors of the physical activity of students determine the complexity of its promotion. Notably, in the social–ecological model, the individual factor lies at the core level, and other levels vary according to the characteristics of the individual factor. Students are a collective term that generalizes childhood and adolescence, and the variation in key factors that influence physical activity within this group is enormous. The reason is that the physiological and psychological developmental and behavioral characteristics of individuals in the core stratum are significantly different for children (elementary school level), adolescents (secondary school level), and early youth (university level), as their growth, and developmental stages continue to change. For example, the key factors that influence participation in physical activity in the target group of first-year elementary school students are extremely different across levels from those influencing the group of first-year college students. However, the existing studies tend to report school-segment similarities in terms of the content of intervention, such that the exploration of physical health promotion among students overlooks the developmental and behavioral characteristics of students at varying school levels. Therefore, the examination of physical activity behavior and intervention for the promotion of physical health among students needs to fully consider the developmental and behavioral characteristics of students across school segments.

This study aimed to analyze the current status of daily SB and PAL among students. Physical activity was categorized into low-intensity (LPA), moderate-intensity (MPA), and high-intensity (VPA) physical activities by investigating seven-day SB and PAL as well as differences in the physical activity of students aged 9–23 years. The results were analyzed according to age and school segment to provide a strong practical basis for further proposals on effective interventions.

The present study found that the overall mean MVPA (60.40 min/day) of university, secondary, and elementary school students met the recommended amount of physical activity (MVPA ≥ 60 min/day) proposed by the WHO. In the total sample, 41.2% of the children and adolescents met this recommended amount. The current findings were higher than those of previous studies, such as Wang, who found that only 5.6% met the recommended amount after testing 3,121 students from second grade to second grade of high school in 11 cities across China (7). The reason for this result may be due to the large geographical differences in the PALs of the students. Yu (33) observed a geographical variability in the PALs of students, which is influenced by local economic, cultural, educational, and physical education class settings after a survey of students in the Zhejiang, Guangdong, Beijing, and Yunnan provinces of China.

The current survey demonstrated that the total sample spent 598.47 ± 162.63 min/day (approximately 10 h) in daily SB. Studies in other countries illustrated that adolescents spend approximately 6–8 h per day in a sedentary position (34–36), and the findings of the present study are greater than those of studies conducted in other countries. This result pointed to excessive daily SB among the students. Physical inactivity not only refers to the lack of health-promoting physical activities, such as housework, and commuting, but also includes another important concept, that is, SB. This behavior cannot be simply understood as the lack of health-promoting physical activities (i.e., moderate and above-intensity physical activity); instead, it is a state of behavior characterized by continued and prolonged sitting and lying down and the lack of whole-body activities such as sitting still and watching television (37). SB is generally considered to be no more than 1.5 METs in intensity (38). Tremblay et al. (39) conducted a systematic review of 232 studies and concluded that a dose–effect relationship exists between SB and health risks in school-age children and adolescents (ages 5–17 years), where an SB of >2 h/day leads to changes in body composition, decreased body mass, low levels of self-esteem, and pro-social behavior. Evenson et al. (40) defined a sustained sedentary session as ≥30 min in which approximately 80% of the time is spent on less than 100 steps per min.

The study found a significant variability in physical activity across school levels. Measured using the ActiGraph accelerometer, the results demonstrated the following trend: college male students > elementary school male students > junior high school male students > high school and college female students > high school female students > elementary school female students > junior high school female students. Specifically, the study observed the following trends for VPA: high school students > elementary school students > junior high school students > college students and MVPA: college students > high school students > elementary school students > junior high school students. Troiano et al. (41) analyzed accelerometer data from a representative nationwide health and nutrition survey conducted in the United States and found that PALs tended to progressively decline from the childhood to the adolescent stages, with attainment decreasing from 42% at ages 6–11 years to 8% at the adolescent stage and continuing to decline into adulthood. A study with a sample size of 1,032 children (aged 9 years at baseline testing) measured by an accelerometer and followed up for 6 years found that MVPA decreased from 180 min/day at age 9 years to 50 min/day at age 15 years with a decreasing trend of 35 min/day per year (42). A national survey in Canada on 21,271 children (aged 5–12 years) and 12,956 adolescents (aged 13–19 years) used pedometer measurements and found that step counts peaked at age 10 years and gradually decreased thereafter (43). Evidently, the gradual decrease in physical activity as children transition from childhood to adolescence (41, 42) is a widespread international problem that warrants scholarly attention.

During the survey, the study found that one of the high schools, with the unique advantage of being built on a mountain, arranges a weekly 40 min hillside run for the class as a group. The school offered 100% attendance for extra credit in physical education class and 80% attendance for passing. If the students did not achieve the 90% attendance, they would be scheduled to compensate for the run at the school playground at the end of the period. Moreover, a time limit was observed for the entire phase of the hill run in which each class has its own timeline and needs to return at the specified time. During the survey, after interviewing the students who had just finished running, the researchers learned that the hill running activities were extremely intense and that the students felt exhausted after each run, which explains the reason for why these high school students produced the most participation time in HPA.

In addition, one of the universities developed a program called “Campus Sunshine Run Intelligent Management System” with the objective of improving the physical health of its students, forming exercise behaviors, and developing a healthy lifestyle. Through this system, the students can participate in independent and self-help activities in the management of sunshine long-distance running and implement scientific and in-class and out-of-class teaching of sunshine long-distance running. The system adopted a full wireless network mode, through which the students can participate the independent and self-help management. Moreover, the system adopted the full wireless network mode to realize wireless data collection, which covers the entire campus through a self-organized network. Swipe card terminals distributed in the whole school wirelessly transmitted the sports swipe card information of the students to the base station for receiving data. It also used face color monitoring technology to achieve an anti-cheating management function in monitoring the students. The university required that freshman and sophomore students conduct sunshine long-distance running exercise for 10 weeks per semester. Each long run is no more than 1,500 m for female students and 2,000 m for boys. The students can obtain 100 points for a total of 30 runs per semester or 20 runs to pass (60 points), which is more than the required number of times for giving additional points. The long-distance running score accounted for 20% of the total physical education score. During the survey, the students were interviewed after the physical education class and learned that the majority of them could maintain the frequency of participating in long-distance running at twice per week, which well explains why the college students displayed the longest duration of time for MPA.

This is a study that investigated the physical activity of school-age children from 9 to 23 years old using accelerometer measurements and analyzed the characteristics of the variability of physical activity behaviors of students in different age groups. In terms of measurement methods this study circumvents the disadvantages of survey methods such as physical activity questionnaires and physical activity diary recall records that are subjectively influenced and difficult to recall. However, it also has some limitations. Due to the vast territory of China and the difficulty of sampling, the survey population did not cover all regions of China. In order to make the survey population more representative, students from urban schools, suburban schools, and schools in combined suburban areas were selected for this study.

This cross-sectional study used the accelerometer for tracking the daily SB and physical activity of the students for one week and found that they were physically inactive and mainly sedentary. Moreover, the study found the following trend, that is, participation in MVPA time decreased, and sedentary time increased with the increase in age. It further a variability in the SB and physical activity of the students in age and school segment. Based on the behavioral characteristics of students across school segments, this study concluded that interventions targeting students' physical activity and physical health should be school segment specific. The results of the study provide a basis for future analysis of factors influencing students' physical activity behaviors across school segments and for proposing targeted intervention strategies for the future.