In China, every year, college students at the national level are required to take the National Student Physical Fitness Test, which evaluates body composition [i.e., body mass index (BMI) in kg/m²], cardiorespiratory fitness [800-m running (female)/1,000-m running (male)], muscular strengths endurance [numbers of curl-ups (female) and pull-ups (male) completed in 1 min], explosive leg power [distance of a standing long jump (in cm)], the flexibility (sit and reach), velocity (50-m running), vital capacity, and sight (Guo et al., 2019). The problem of college students' physical decline has still not been effectively addressed as reflected by the test results. Nevertheless, for a long time, people have paid more attention to college students' academic performance but have ignored their mental health and physical health. College students who fail the National Student Physical Fitness Test are more likely to be vulnerable to multiple physical (e.g., overweight, obesity, and underweight) and mental health problems (e.g., depressive symptoms, anxiety, and negative affect) that keep them off from participating in physical activities.

Subjective exercise experience is defined as the subjective feeling and emotional response toward exercise after participating in physical exercise, including positive wellbeing, psychological distress, and fatigue dimensions (MeAuley and Courneya, 1994). Subjective exercise experience is an important predictor of actual exercise behavior (Jiang, 2022). The positive effects of physical exercise on psychological wellbeing have been proven in previous research (Kwan and Bryan, 2010). Abundant evidence showed that people with a positive exercise experience can correctly understand the value and significance of exercise, and positive affective response to exercise contributes to adherence to an exercise regimen (Williams et al., 2008). On the contrary, those who have negative exercise experiences will avoid physical exercise practice and hardly form positive and regular exercise behaviors (Wu et al., 2016). Physical exercise is positively correlated with the subjective wellbeing of college students (Shang et al., 2021). Physical activity can reduce depression levels and can increase the sense of wellbeing among people with mental disorders (Li et al., 2022). Different exercise categories, such as frequency and intensity of exercise, have different degrees of impact on mental health (Duan, 2014). Positive exercise experience helps to enhance the exercise desire, making the students more willing to participate in the exercise actively, whereas negative exercise experience suppresses the exercise intention, weakens the intensity of the exercise motivation, and limits the implementation of the plan (Dong and Zhang, 2016). Both the intensity of physical exercise and the duration of physical exercise can have a significant impact on subjective and psychological wellbeing. The greater the intensity of physical exercise, the stronger the subjective happiness (Li and Liu, 2014).

Most scholars believe that participating in physical activities will have an impact on emotional experiences. Small- and medium-intensity physical activity have a significant impact on individual positive emotional experiences. Appropriate exercise intensity can improve the positive emotional state and reduce the negative emotional state, which has an obvious effect on improving the overall level of positive wellbeing and reducing psychological fatigue (Dong, 2004; Wang and Yan, 2006). Research studies showed that intensive activities can increase happiness in college students, which in turn eliminates psychological disturbance (Lin and Xu, 2020). Leisure sports can help college students to effectively eliminate fatigue, but their effects on improving positive wellbeing and distress are not obvious (Meng, 2015). Currently, there are many studies on physical activity and subjective exercise experience targeting various groups, including children and adolescents, university students, and older adults (Wang and Zhao, 2018; Smith and Hanni, 2019; He et al., 2022). However, the question of whether the effects can be generalized to physically vulnerable college students is still unclear.

The COVID-19 pandemic and associated lockdowns increased the prevalence of anxiety and depressive disorders worldwide, people have less opportunity to participate in exercise (Rahim et al., 2021; Lokman and Bockting, 2022). However, doing some physical activity had lower risks for severe COVID-19 outcomes, including death, than those who were consistently inactive (Sallis et al., 2021). Mandatory physical education (PE) for college students showed tremendous changes among them, especially in Wuhan city. All the PE classes switched to online mode. TikTok, YouTube, and other apps were a few sources of reference for the practice of physical exercise during the COVID-19 outbreak (Vancini et al., 2021). However, the teaching objectives are difficult to achieve due to the limitation of equipment and field. At the same time, the potential burden on psychological health has appeared (Burhamah et al., 2020). In the spring and winter of 2021, although the COVID-19 confirmed cases had significantly declined and it began to resume normal PE, the physical fitness of college students continues to decline compared with aforetime. However, it is unclear how students' subjective exercise experience has changed since the outbreak of the pandemic.

Understanding subjective exercise experience and its predictors carry essential implications for PE in the post-COVID-19 era. Currently, there is scarce evidence that focuses on physically vulnerable college students, which does not mention psychological symptoms (anxiety and depression) that determine their subjective exercise experience and psychological wellbeing. If college students experienced high positive wellbeing after participating in the PE, it will motivate their insistence to exercise, especially for those physically vulnerable college students. The present study used latent profile analysis (LPA) to explore the latent class of subjective exercise experience among physically vulnerable college students who scored 59 points or less on tests under the National Student Physical Health Standard (Zhou et al., 2008).

After the outbreak of the pandemic, universities postponed the spring semester, and all classes were converted to online mode, including the PE. The mental health of college students was not optimistic amid the pandemic. For college students, extended holidays, long-term stay at home, and unable to go to school to participate in social activities can increase feelings of anxiety and depression (Chang et al., 2020). Acquisition of positive wellbeing through physical exercise can improve depressive symptoms (Wang, 2021). Even more, moderate-intensity exercise could cut down antidepressant use (Vancampfort et al., 2017).

Research show that even though students understand the importance of PE, they hardly take action because of the limited space at home and the teacher cannot supervise them (Lin and Xu, 2020). This can partially explain our finding that students in the BMI health group gradually decreased since the outbreak of the COVID-19 pandemic, while the other three groups, namely, obese, overweight, and underweight groups increased. Students' physical fitness continues to decline after the end of the pandemic, and this phenomenon reminds us to pay attention to PE.

Although past research has supported the three dimensions of subjective exercise experience (MeAuley and Courneya, 1994), profiles of subjective exercise experience among physically vulnerable students have yet to be established. Men experienced more positive subjective exercise experience compared with women, characterized by high positive wellbeing, low psychological distress, and fatigue. This finding is consistent with the findings of the gender differences in physical activity that men have more healthy physical exercise behavior than women to achieve the same performance (Wang and Yan, 2022). The reason for this result may be that, if female students want to do the same amount of exercise as males students, they have to pay double, or even many times the effort, which may reduce their positive subjective exercise experience. At the same time, the somatic reaction after finishing the exercise also aggravates psychological distress and fatigue (Tao, 2013). Therefore, gender differences should be taken into account in PE, specifically to adjust physical demands and exercise intensity for male and female students. Depressive symptoms are more likely to trigger the psychological fatigue component of the subjective exercise experience. We should not blindly pursue high-intensity and long-time exercise since exercise intensity and exercise time can be maintained at a moderate level.

Several limitations of the present study warn concerns. First, subjective exercise experience was measured by the self-reported instrument. Future studies may consider using both subjective and objective measures to cross-validate physical exercise experience. Second, a convenient sampling method was used, which impeded the generalization of the research findings. Finally, the cross-sectional study design cannot verify the potential reverse causation. Therefore, a longitudinal design is encouraged in future studies.

Using LPA, we identified three profiles of emotional response toward physical exercise among physically vulnerable students in terms of positive wellbeing, psychological distress, and psychological fatigue. The prevalence of the three profiles had similar distribution among the students. Gender, depression, and anxiety were all found to predict class membership, which was consistent with previous literature highlighting the poor exercise experience of women and individuals with depressive or anxiety symptoms (Ivancic et al., 2016). The hallmark of the present study is that it tested the three salient stages of COVID-19 in China concerning reports of The National Health Commission of China, and supported that students in the emergency containment stage were more likely to experience exercise fatigue compared with students in the dynamic zero clearance stage. The present study has called for attention to these factors when implementing programs for physically vulnerable college students in PE.

The raw data supporting the conclusions of this article will be made available by the authors upon request, without undue reservation.

The studies involving human participants were reviewed and approved by Ethics Committee of Zhongnan University of Economics and Law. The patients/participants provided their written informed consent to participate in this study.

Conceptualization and writing—original draft preparation: JL and HL. Methodology, software, formal analysis, investigation, resources, data curation, supervision, project administration, and funding acquisition: JL. Validation and writing—review and editing: MX, HH, and HL. Visualization: MX. All authors have read and agreed to the published version of the manuscript.