Relationship of the number of days of participation in school physical education classes in a week with body mass index, number of hospital treatments for school violence, and mental health status among Korean male adolescents

2.1 Data collection

We collected the data of 51,850 individuals who had participated in the 2022 Korea Youth Risk Behavior Survey (KYRBS). We excluded the data of 1397 individuals whose information regarding the study topic was not available. Among the data of the remaining individuals, we extracted and used the data of 25,749 male adolescents. The KYRBS is a self-administered annual survey conducted by the Korea Disease Control and Prevention Agency. Adolescents participate in this survey using computers or mobile devices at their school.

2.2 Measures

2.3 Data analysis

All statistical analyses were performed using SPSS for Windows (version 23.0; IBM Corp., Armonk, NY, USA). First, we conducted a frequency analysis of respondents’ characteristics, such as age, school type and residential area, number of days of participation in physical education classes, BMI, the number of hospital treatments for school violence, depressive symptoms, suicidal ideation, stress and loneliness. Second, we conducted chi-square analyses to identify differences in respondents’ characteristics, BMI, the number of hospital treatments for school violence, depressive symptoms, suicidal ideation, stress and loneliness based on the number of days of participation in physical education classes in a week. Third, we performed multivariate logistic regression analyses to examine the association of the number of days of participation in physical education classes in a week with BMI, the number of hospital treatments for school violence, and mental health status. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. Statistical significance was set at p < 0.05.

3.1 Respondents’ characteristics, number of days of participation in physical education classes, BMI, the number of hospital treatments for school violence, depressive symptoms, suicidal ideation, stress and loneliness

Table 1 presents the details of respondents’ characteristics, number of days of participation in physical education classes, BMI, the number of hospital treatments for school violence, depressive symptoms, suicidal ideation, stress and loneliness.

3.2 Differences in respondents’ characteristics, BMI, the number of hospital treatments for school violence, depressive symptoms, suicidal ideation, stress and loneliness based on the number of days of participation in physical education classes participation in a week

Table 2 presents the results of chi-square analyses. A statistically significant difference was found in age (χ² = 3866.612, p < 0.001), school type (χ² = 4506.476, p < 0.001), academic level (χ² = 428.502, p < 0.001), perceived health status (χ² = 389.447, p < 0.001), BMI (χ² = 173.221, p < 0.001), the number of hospital treatments for school violence (χ² = 17.173, p = 0.046), suicidal ideation (χ² = 15.927, p = 0.001), stress (χ² = 29.327, p < 0.001), and loneliness (χ² = 17.792, p < 0.001).

3.3 Association between the number of days of participation in school physical education classes in a week and BMI

Table 3 presents the results of the analysis of the association between the number of days of participation in school physical education classes in a week and BMI. The average OR (95% CI) between the number of days of participation in school physical education classes in a week and being healthy was 1.171 (1.034–1.326, p = 0.013) among respondents who participated once a week, 1.201 (1.080–1.336, p = 0.001) among respondents who participated on two days, and 1.311 (1.181–1.456, p < 0.001) among those who participated on three or more days. The average OR (95% CI) between the number of days of participation in school physical education classes in a week and being overweight was 1.157 (1.014–1.320, p = 0.030) among respondents who participated on three or more days. The average OR (95% CI) between the number of days of participation in school physical education classes in a week and being obese was 1.139 (1.013–1.281, p = 0.030) among respondents who participated on three or more days.

3.4 Association between the number of days of participation in school physical education classes in a week and the number of hospital treatments for school violence

Table 4 presents the results of analyzing the association between the number of days of participation in school physical education classes in a week and the number of hospital treatments for school violence. Among respondents who received hospital treatments 1–2 times for school violence, no statistically significant OR was found. The average OR (95% CI) between the number of days of participation in school physical education classes in a week and receiving hospital treatment 3–4 times was 0.454 (0.252–0.818, p = 0.009) among respondents who participated in physical education classes once a week and 0.556 (0.354–0.876, p = 0.011) among those who participated on two days. Furthermore, the average OR (95% CI) between the number of days of participation in school physical education classes in a week and receiving hospital treatment 5 or more times was 0.504 (0.258–0.986, p = 0.045) among respondents who participated in physical education classes on two days.

3.5 Association between the number of days of participation in school physical education classes in a week and mental health status

Table 5 presents the results of the analysis of the association between the number of days of participation in school physical education classes in a week and mental health status. The average OR (95% CI) between the number of days of participation in school physical education classes in a week and not experiencing suicidal ideation was 1.259 (1.079–1.468, p = 0.003) among respondents who participated once a week. The average OR (95% CI) between the number of days of participation in school physical education classes in a week and not experiencing loneliness was 0.854 (0.776–0.940, p = 0.001) among respondents who participated once a week, 0.806 (0.742–0.876, p < 0.001) among those who participated on two days, and 0.768 (0.705–0.836, p < 0.001) among those who participated three or more days. No statistically significant ORs were found for depressive symptoms and stress.

4.1 Interpretation of the findings

This study examined the association of the number of days of participation in school physical education classes in a week with BMI, the number of hospital treatments for school violence, and mental health status among Korean male adolescents. The results revealed that the more Korean male adolescents participate in school physical education classes in a week, the more likely they are to report that they were healthy, overweight and obese. The more they participate in school physical education classes in a week, the less often they are treated for school violence in hospitals. Furthermore, the more they participate in school physical education classes in a week, the less likely they are to experience suicidal ideation but more likely to feel lonely.

We first found that the more Korean male adolescents participate in school physical education classes in a week, the more likely they are to report that they were healthy, overweight and obese. This finding indicates that physical activity alone is unlikely to reduce weight or prevent obesity in adolescents. These findings are partly consistent with those of Sabia et al. [10] who found that despite a 10%–13% increase in school physical education time, there was no effect on weight loss among adolescents. Bednar et al. [11] used data from the 2010–2011 Early Child Longitudinal Survey Kindergarten Class to examine the effect of physical education classes on children’s weight. They found no direct effect on the weight of elementary school students in the United States. These findings suggest that participating in physical activity in physical education classes does not help adolescents lose weight or prevent obesity. Some studies have reported that physical activity alone is not effective for weight loss and obesity prevention; rather, physical activity combined with diet control are most effective [12]. Meanwhile, Erfle et al. [9] conducted a study on the effect of participation in physical education classes on adolescents’ physical fitness and weight and found that participation in physical education has a greater effect on strengthening physical fitness than reducing weight. In other words, the results of this study and previous studies suggest that participating in physical education classes is more effective for improving physical fitness than reducing weight and that dietary education should be combined to prevent and manage obesity in adolescents.

Second, we found that the more Korean male adolescents participate in school physical education classes, the less often they are treated in hospitals for school violence. Locke, who reinterpreted Juvenalis’ proposition, said, “A sound mind in a sound body” or a healthy body leads to a sound mind. According to Juvenalis’ thesis, since school violence is a negative behavior related to the mind and virtue, it will decrease if the body is healthy [13]. Many studies have reported that adolescents’ participation in physical education classes reduces school violence, which is partially consistent with the results of this study, and school sports should be considered a fundamental and practical solution for school violence [7, 8]. It is important to solve problems, and the best solution is to prevent and minimize the occurrence of problems. Therefore, it may be possible to prevent school violence by developing and implementing programs in physical education classes to curb school violence.

Third, we found that the more Korean male adolescents participate in school physical education classes, the less likely they are to experience suicidal ideation. This finding aligns with that of previous studies that found that adolescents’ participation in physical activity helps reduce suicidal ideation [14, 15]. Furthermore, our finding is partly consistent with those of Felez et al. [16], who explored the association between physical activity and suicide attempts among adolescents in 48 countries. Felez et al. [16] found that, in contrast to female adolescents, male adolescents are less likely to attempt suicide if they engage in high levels of physical activity, suggesting that participation in school physical education classes is effective for improving the mental health of male adolescents. Potential ways to prevent suicide have not been investigated, but physical activity may help prevent it [15]. Engaging in physical activity can be a low-cost solution, and unlike traditional mental health interventions, it is generally non-stigmatizing [17]. Since physical activity can reduce suicidal ideation among adolescents, it is necessary to increase the number of days of physical education classes in schools.

Finally, we found that the more Korean male adolescents participate in school physical education classes, the more likely they are to feel lonely. Pels et al. [18] conducted a systematic review of the association between participation in physical activity and loneliness and found that increased participation in physical activity reduces loneliness. Thus, further research is required to determine the effect of physical activity on loneliness.

4.2 Practical implications of the study

Adolescents’ participation in physical activity contributes to their health and well-being throughout their lives, from adolescence in the short term to adulthood in the long term. In particular, physical activity has several benefits, including improved physical fitness and muscle strength, reduced chronic pain, improved bone density, reduced risk of cardiovascular disease, improved weight control and boosted immunity [19]. In addition, on a psychological level, physical activity improves mental health and quality of life, reduces stress and anxiety, lowers the risk of depression and improves sleep quality [20]. In other words, physical activity is associated with overall physical, mental and social health and well-being [21].

Despite these benefits of physical activity, from 2020 to 2022, COVID-19 distancing measures led to a decrease in physical activity and an increase in sedentary time. Gradually, these behaviors have become habits and adolescents’ physical activity habits are in danger of breaking down [19]. Decreased physical activity is associated with the increased likelihood of cardiovascular diseases, weight gain, diabetes, psychosocial problems and negative physical and mental health, which can extend into adulthood [22]. Therefore, the World Health Organization has set a goal of reducing the prevalence of physical inactivity by 15% by 2030 and has provided guidelines for promoting physical activity at the national level [23]. The majority of adolescents meet the recommended standards of physical activity through physical education classes in school. As the lack of physical activity among adolescents is becoming a problem around the world, it is necessary to focus on physical education classes in schools as a measure to promote physical activity among them.

Korea’s physical education curriculum specifies the number of physical education classes adolescents must attend. According to the number of hours of instruction one must receive, students are required to participate in physical education classes at least three times a week [24, 25]. Nonetheless, this study found that 16.8% of Korean male adolescents did not participate in physical education classes, while 15.8%, 31.2% and 36.2% participated once, twice and thrice a week, respectively. This shows that 36.2% of Korean male adolescents participate in physical education classes thrice a week. However, it also shows that 63.8% of Korean male adolescents participate in physical education classes less than three times a week. This means that adolescents participate in physical education classes according to the curriculum but do not engage in active physical activity. This result is a percentage of the number of days that men participate in physical education classes. However, considering that women are not as active as men, it is predicted that Korean adolescents will not participate in physical education classes in schools. In other words, since only 36.2% of adolescents participate in school physical education classes thrice a week, it is necessary to identify measures that increase students’ involvement in physical education classes.

On 31 October 2023, the Korean Ministry of Education announced the 2nd Master Plan for Student Health Promotion [4]. This plan aims to increase the number of physical education classes for elementary, middle and high school students and increase their physical activity [4]. According to the plan, a new physical education curriculum will be established for the first and second grades of primary school, and the current 80 hours will be increased to 144 hours [4]. In middle schools, the number of sports clubs will be increased, and in high schools, credits for physical education will be mandated [4]. It is desirable to establish a physical education curriculum, increase the number of hours students can participate in physical activities, and form a lifelong habit of exercising by making physical activity a habit from an early age. However, since students do not meet the current curriculum’s requirement of participating in school physical education classes thrice a week, efforts must be made to increase physical education time and students’ participation in physical activities.

Physical education classes in schools are the primary means of satisfying the physical activity requirements of children and adolescents [26]. Nonetheless, as this study shows, students do not fully participate in physical education classes thrice a week, the minimum number of hours of instruction required as per the curriculum. Previous studies have cited fear of failure, low athletic performance, lack of self-confidence, and negative reactions from peers as reasons students avoid participating in physical education classes [27, 28]. There can be many reasons adolescents avoid participating in physical education classes. To engage them in class, it is necessary to increase their motivation to participate and encourage them to initiate physical activity instead of eliminating avoidant factors [29]. Considering that the Korean Ministry of Education has announced an expansion in the number of physical education classes, Korea must find ways to create and support an environment where adolescents can take the lead in physical activities. In other words, as the number of physical education classes and consequently, opportunities to engage in physical activity increase, specific and systematic planning and support will be required to realize actual physical movement.

Physical education classes that consider individuality emphasize respecting individual characteristics and motor skill levels to increase the youth’s active and voluntary participation. Digital technology-based physical education classes can encourage adolescents to participate in physical activities voluntarily and proactively. Such classes can allow adolescents to participate in physical activities based on their characteristics. Moreover, they are the need of the hour, considering that we are living in the Fourth Industrial Revolution [30, 31, 32]. Flipped learning allows students to learn online at home and enables the implementation of physical education classes that consider individuality at school [32]. Adolescents can choose and practice different levels of activities online at home and participate in physical activities based on their characteristics at school [33]. Additionally, apps and wearable devices can be used to promote physical activity by providing programs tailored to one’s body [34, 35]. Wearable healthcare technology can measure vital aspects such as heart rate and exercise level with Near-field communication technology and help users manage their fitness and health; thus, they can garner positive responses from students and build their interest in physical activity [36]. In other words, adolescents’ voluntary and active participation can be increased if they are allowed to engage in physical activities tailored to their characteristics through digital technology at schools. However, digitalized physical education classes cannot be realized without the efforts of teachers. Korean teachers are aware of the need for digitalized physical education classes, but they do not know how to design and operate such classes [37]. Therefore, case-based, participatory and practical teacher-training programs are required [38]. Korean physical education teachers are expected to be reborn as experts in planning and managing physical activities rather than being just instructors [39].

4.3 Limitation

This study had several limitations. First, it focused on Korean male adolescents and did not include Korean female adolescents. Therefore, the results cannot be generalized to all Korean adolescents. Second, since this was a cross-sectional and secondary study, it was not possible to establish causal relationships between the variables. Nonetheless, this study holds significance because it focused on the number of days of participation in physical education classes in schools, which has been overlooked in previous studies, and explored its association with BMI, the number of hospital treatments for school violence and mental health status. Furthermore, the results of this study can help determine the direction of physical activity and school sports among Korean adolescents. They can also be used as basic data to develop plans for improving adolescents’ health in countries other than Korea.