In this study, we used the chain mediation model to explain we determined the mediation of sleep problems and psychological resilience between physical activity and social anxiety symptoms among college students. The results of this study suggest that physical activity can not only directly reduce social anxiety symptoms, but also affect social anxiety symptoms through the chain mediation of psychological resilience and sleep problems. The more physical activity, the less it triggered sleep problems, which in turn increased the level of psychological resilience, which decreased the risk of social anxiety and social phobia symptoms. It will provide a new reference for the prevention and intervention of social anxiety symptoms in college students, and will greatly promote the mental health of college students.
4.1 The relationship between physical activity and social anxiety symptoms
The direct association between physical activity and social anxiety symptoms has been proved in this research. Numerous studies have indicated that physical activity and mental health are closely related. A cross-sectional study among Indian college students found that moderate and high levels of physical activity were inversely associated with anxiety and depression[44] (Ghrouz et al., 2019), while a Chinese study found similar results with inactive college students, who displayed more mental health problems[45] (Kayani et al., 2021). These findings suggested that adverse mental health problems might be reduced through increasing the level of physical activity. A randomized controlled trial found that the therapeutic effect of high-intensity interval training on social anxiety was twice that of lower intensity training [46](Plag et al., 2020). In addition, some researchers found that people with more physical activity have lower social anxiety symptoms in cross-sectional studies (r = -0.12, P = 0.003), adults after treatment with physical activity were more effective in reducing social anxiety symptoms than children and adolescents in longitudinal studies (d = -0.22, P = 0.001)[13]. What’s more, there are some hormone secretion and neurobiological mechanisms that could explain the relationship between physical activity and social anxiety symptoms. Researchers believe that the symptoms of social anxiety may be related to the peripheral blood oxytocin, which has the effect of reducing anxiety and can promote individuals to engage in more prosocial behaviors during social interactions, which could improve their social anxiety symptoms[47]. Meanwhile, an animal experiment confirmed that physical activity has a significant positive effect on peripheral blood oxytocin[48]. Another study indicated that physical exercise could alter amygdala reactivity and functional connectivity, which strongly associated with fear and avoidance, and in response to explicit and implicit emotional processing[49–50]. However, these are only a part of the explanations, and the biological mechanism of physical activity and social anxiety symptoms needs to be further explored by more researchers.
4.2 The mediating role of psychological resilience
In this study, the mediating effect of psychological resilience that when college students perform more physical activity, the higher level of psychological resilience they will have, and this will decrease the occurrence of social anxiety symptoms. The mediation effect of psychological resilience between the physical activity and social anxiety symptoms reached about 30%. This result echoes previous studies, such as resilience is an important mediator between physical activity and mental health in Hong Kong Chinese adolescents, which contributed to 60% of this relationship[51], and adequate physical activity can increase the use of "self-sufficiency" and "perseverance" resilience components in the elderly, thus improving mental well-being[31]. Based on the process-oriented perspective in the resilience theory, resilience is developed by individuals overcoming the adverse effects of exposure to dangerous and traumatic events, which is a result of the interaction between individuals and the environment[52]. Physical activity is often accompanied by challenges, self-improvement and goal attainment. In the course of the exercise, individuals need to socialize by constantly assimilating and adapting to their surroundings, assist them acquire the skills and abilities to better negotiate[53]. Therefore, perform more physical activity may be a booster of psychological resilience. Additionally, people with good psychological resilience have better adaptability and higher emotional regulation skills when faced with some stressful and frightening social situations, and reduce social anxiety symptoms[26–27]. What’s more, a review study revealed the molecular and neurobiological mechanisms involved in the beneficial effect of physical activity on the resilience of the brain to stress, regular physical activity has a positive effect on the central nervous system functions, which is correlated with increased neurogenesis, increased neurotrophic factor expression, modulation of neurotransmission and HPA activity, reduced brain inflammation and oxidative stress, and improved cognition[54]. In this context, resilient animals do not show social avoidance and depression-or anxiety-like behavior, etc. Instead, they exhibit motor activity like active exploratory behavior[55]. Therefore, this study complements evidence in the area where physical activity alleviates social anxiety symptoms in college students by enhancing psychological resilience.
4.3 The mediating role of sleep problems
In this study, we verified the mediating effect of on physical activity and social anxiety symptoms, and more physical activity, which will reduce sleep problems of college students, and better sleep quality will decrease the symptoms of social anxiety, where sleep problems explains 8.11% and 9.09% of the relationship between physical activity and social anxiety and social phobia, respectively. Similar relationships have also been confirmed in previous studies. Fontana et al. found that involvement in high levels of physical activity was 40% more likely to have good quality of sleep, and in turn, teachers with high sleep quality were 75% less likely to have high stress[56]. Instead, a longitudinal study found that sleep problems have a mediating effect on the association between passive sedentary behavior and major depressive disorder[57]. In other words, sleep quality is an important behavioral mechanism between physical activity and mental illness. There are several shared mechanisms that explain the effect of sleep problems in the association between physical activity and social anxiety symptoms. Physical exercise was an effective strategy to reduce the level of cortisol, which is commonly used as a biomarker indicating dysregulation of the HPA axis, associated with lower symptoms of social anxiety[58–59]. At the same time, sleep was often used as a non-pharmacological way of enhancing exposure therapy for treating social anxiety disorder, which neurobehavioral basis was fear extinction[60]. This may be because sleep could strengthen and generalize to lost learning and memory, while sleep disturbances can disrupt these same processes[60]. Furthermore, sleep brought some minor biomarker alterations, showed a trend towards reduced psychophysiological and cortisol responses to social stressor tasks[61]. Thus, sleep problems may be one of the important mediators of physical activity in reducing social anxiety symptoms among college students.
4.4 The chain mediating effect of sleep problems and psychological resilience
Our study discover that psychological resilience and sleep problems play a role of chain mediation in the relation between physical activity and social anxiety symptoms (social anxiety and social phobia) in college students, the effect values of this pathway accounted for 4.05% and 4.55% of the total effect, respectively. In other words, we find that if college students experience more physical activity, they may have a higher level of resilience to life stress and less sleep problems, and this high sleep quality will further decrease the occurrence of social anxiety symptoms, which further explained the mechanism by which physical activity affects social anxiety in college students. Additively, psychological resilience has a positive impact on the quality of sleep[62]. High resilience means that the activity of the ventromedial prefrontal cortex, which is a pathophysiological consequence of sleep disruption. This may explain that higher resilience scores predict overall better sleep quality and shorter sleep latency[63]. Li et al indicated that they received material and spiritual support from family, peers and society during the physical activity, which met their growth needs for love and respect, and that prompted them to actively develop good traits, improve psychological resilience and social adaptation, and thus improve the quality of sleep[64]. Previous studies have shown that physical activity has been used as a supplement to cognitive-behavioral therapy to treat social anxiety disorders[13], our findings suggested that some psychological therapies such as improving psychological resilience or decreasing sleep problems could also be used as a supplement or substitute. Generally, the results of this study complement the internal complex pathways of physical activity, psychological resilience, and sleep problems improving college students’ social anxiety symptoms, which provides new strategies for developing more targeted psychological interventions to improve the mental health of college students.