The onset of the COVID-19 pandemic in 2020 launched global concern regarding the high rates of psychological distress among adolescents throughout the scientific community. While adolescent mental health was already of great interest long before the COVID-19 pandemic (1–3), the context of this global health crisis exacerbated its relevance. Indeed, due to the restrictive health measures implemented, social contacts were greatly reduced, testing adolescents' ability to adapt and challenging their psycho-emotional development (4–6). Considering this situation, researchers quickly recognized the necessity to better understand the potential short, mid, and long-term consequences of the COVID-19 pandemic on youth mental health to mitigate its negative impacts (7).

Exercise is known to reduce anxiety and stress symptoms (8, 9), psychological difficulties (10–13) as well as diminish symptoms of depression (14–16). Côté and Fraser-Thomas (17) have investigated the effects of physical activity on the development of young people in general. The most frequent benefit of physical activity is undoubtedly in the area of physical health (lifestyle habits, cardiovascular health, body weight, muscular strength and flexibility, etc.) (17, 18). Sports and physical activity also boost self-esteem and reduce stress, contributing to young people's emotional development and general well-being (17). A longitudinal study comparing inactive, beginner, and active individuals found that regular physical activity was positively associated with higher levels of happiness, self-esteem, and life satisfaction (19). Among adolescents, participation in sports and the development of athletic skills have been associated with lower levels of depression (20, 21) and decreased risks of depression and suicidal ideation, notably through improved self-esteem (22). Moreover, a study has shown that, among young adults, maintaining a daily routine and engaging in physical or sport activities were among the coping strategies associated with lower distress during the COVID-19 pandemic (23).

The links between physical activity interventions and mental health (24, 25) as well as psychosocial adjustment (externalizing problems, internalizing problems, self-concept, academic achievement, mental health disorders) (26, 27) are therefore well established, beyond the scope of the COVID-19 pandemic. To this end, the World Health Organization (WHO; 28) recommends that adolescents engage in moderate aerobic physical activity for an average of 60 min per day (7 hours a week). Yet, leisure-related physical activity among adolescents aged 12–17 years of age fell from an average of 27 min a day in 2018 to 20.3 min a day in 2020, equivalent to 3.15 h a week in 2018 and 2.4 h a week in 2020, well below the WHO recommendations (29). Indeed, research suggests that physical activity (activity time per week) among adolescents decreased, and sedentariness increased during the COVID-19 pandemic in relation to the health measures imposed (30). Although physical activity is recognized as beneficial for one's mental health, findings from the literature are nonetheless divided on dose and intensity required to obtain the associated benefits. Indeed, it is possible that when an individual reaches a certain level of physical activity in terms of performance requirements and time devoted to practice (e.g., recreational, competitive or elite sport), mental health benefits diminish as the pressure to perform increases (31, 32). The present study focuses on recreational participation in physical activities and sports.

A literature review conducted in the early months of the COVID-19 pandemic (12) and including 21 studies found that people who engaged in regular physical activity, in terms of duration and frequency, had fewer symptoms of depression and anxiety. This is also the conclusion reached by a review of the literature on the links between physical activity and mental health during the COVID-19 pandemic, which included 23 studies conducted in China in 2020 and 2021 (33). For adolescents specifically (13–18 years), a literature review (34) examined changes in physical activity after the onset of the COVID-19 pandemic and their impact on well-being. Combining 15 studies, the authors concluded that greater physical activity was associated with greater well-being, altered eating habits and free time, and an increase in obesity and internalizing symptoms (including anxiety and depression). Another recent literature review (35), based on 14 studies, reported on the links between physical activity and psychological or behavioral problems in children and adolescents during the COVID-19. Overall, a significant protective effect of physical activity was found on depression, anxiety, stress, mood problems, and behavioral problems such as irritability, problems with friends, conduct problems, hyperactivity or inattention, and prosocial behaviors.

In the same vein, an initial study by our research team found that adolescents who continued to engage in physical activity in the early months of the COVID-19 pandemic were less likely to experience psychological distress compared to those who stopped their activities (36). This is consistent with the results of a study conducted in Brazil during the early months of the COVID-19 pandemic. The authors reported that physical activity (more than 30 min of moderate activity or more than 15 min of vigorous activity per day) was associated with less symptoms of depression and anxiety, whereas a sedentary lifestyle (sitting more than 10 h a day) was associated with more symptoms of depression and anxiety (37). A Chinese study (38) also found a link between higher levels of physical activity in the past 7 days and more positive mood scores (less tension, depression, anger, fatigue, and confusion and more vigor and self-esteem) in adolescents during the COVID-19 pandemic.

While these studies add significantly to our understanding of the benefits of physical activity during the COVID-19 pandemic, their findings are mostly cross-sectional such that the effects of physical activity on adolescents' mental health over time during the pandemic are scarce. Assessing the effects of physical activity on young people's mental health six months following the onset of the COVID-19 pandemic is particularly pertinent as the uncertainty related to this unprecedent crisis and associated restrictions persisted and even spiked in certain regions, namely Quebec. As such, it is imperative that further research shed light on the factors that protect against worsening distress over time.

To this end, a Canadian study (39) with four measurement times from April 2020 (T1) to summer 2021 (T4) found that higher levels of vigorous activity across the COVID-19 pandemic (averaged across the four time points) was a significant negative predictor of depression, as well as anxiety, at T4. Higher activity levels also promoted greater self-esteem at T4. Though Covid-19 related stress at T1 predicted greater feelings of loneliness, depression, anxiety and lower self-esteem at T4, adolescents' engagement in physical activity buffered against anxiety and was related to greater self-esteem at T4. In addition to shedding light on the longitudinal association between physical activity and psychological adjustment during the COVID-19 pandemic, the findings also underscore the benefits of physical activity on self-esteem.

In general, self-esteem is recognized as a protective factor against psychological distress (40) and can be promoted by sport participation (22, 31). A study from the United Kingdom reported on the protective effect of physical activity on perceived stress through self-esteem as a mediating variable (38). The practice of physical activity was found to be positively related to better self-esteem, which in turn was associated with less perceived stress and less anxiety and depression (41). An additional study (39) also put forward this association between sports practice and lower depression in 14- and 15-year-old adolescents through greater self-esteem. These findings support that physical activity may be indirectly related to perceived stress, and anxiety/depressive symptoms through self-esteem.

Overall, previous research supports that physical activity is related to greater mental health and self-esteem and that these associations held true during the COVID-19 pandemic. Yet, findings rely largely on concurrent data, and none assess the effects of greater physical activity at the start of the pandemic on later psychological distress, controlling for initial levels of distress. Moreover, while some research suggests a potential mechanism through self-esteem (22, 41, 42), none of these have investigated these associations using a longitudinal design. Does increased physical activity contribute to a reduction in psychological distress throughout the COVID-19 pandemic? Is self-esteem a potential underlying mechanism in this relationship? The following study aims to shed light on these important questions.

Descriptive statistics of main study variables are presented in Table 1. On average, adolescents were physically active for 4.2 h (SD = 1.9) over the last 7 days, representing less than an hour a day. Bivariate correlation coefficients (Table 2) show that greater HPA, as measured by time spent engaging in physical activity over the past week, was associated with greater self-esteem. Greater self-esteem at T1 was related to less psychological distress at T2. The bivariate correlation between HPA and psychological distress at T2 was non-significant, which justifies testing an indirect link rather than mediation. Considering that psychological distress at T1, gender and age were associated to psychological distress at T2 with a p-value < .25, they were considered as covariables in the tested model (see Figure 1).

Results confirmed an indirect mechanism (95% C.I.: −2.281, −0.179). Namely, greater hours engaging in physical activity in the past week was related to greater self-esteem at T1 (b = 0.628, se = 0.229, p = 0.006, β = 0.203). Greater self-esteem at T1 was in turn related to lower psychological distress at T2 (b = −1.499, se = 0.475, p = 0.002, β = −0.335), controlling for distress at T1, gender, and age. Lastly, hours spent engaging in physical activity in the past week were not linked to psychological distress at T2 (b = 1.410, se = 1.305, p = 0.280, β = 0.101), controlling for distress at T1, gender, and age. The results thus support that physical activity is indirectly and negatively associated to psychological distress through self-esteem. We also tested the model without controlling for distress at T1 and the results provide a similar patten of results (Supplement Material Table 4).

These results support that the practice of physical activity during a time of tumult can have mid-term benefits on mental health adjustment through its association with self-esteem. Indeed, the practice of physical activity in the past 7 days was linked to greater self-esteem among the participants of the study. Participants with greater self-esteem then presented fewer symptoms of psychological distress 6 months later, during the prolonged period of uncertainty of the COVID-19 pandemic.

Using a longitudinal design, the present findings significantly add to the breath of empirical evidence supporting the benefits of physical activity in promoting greater psychological adjustment over time though greater self-esteem. These findings echo the assumption that physical activity and participation in sports are minimally invasive “interventions” (54) with significant benefits for mental health. As such, ensuring that youth maintain opportunities to participate in sports and physical activities by providing continued access to sports facilities and adapting, if necessary, organized sports activities during times of crisis and turmoil seems essential as it is linked to their self-esteem, a factor associated with better psychological health over time (22, 31, 32, 42). Physical activity can lead to a sense of personal competence and gratification through physical achievement, which in turn can boost self-esteem. In turn, improved self-esteem can ensures better mental health; a feeling of being a person who has something worthwhile to offer could protect against mental health difficulties.

A major contribution of the present study is the assessment of the indirect model while controlling for initial distress among adolescents. This allowed us to tease apart the unique contribution of physical activity and self-esteem in predicting psychological distress over time. Nonetheless, certain limitations need to be addressed. First, nearly two-thirds of participants were girls, limiting the generalizability of study findings. This over-representation of adolescent girls is typical within social-sciences research and has also been the case in studies using social medias as a recruitment strategy (55). Nevertheless, we controlled for gender in the present study, mitigating the impact of this limitation. Additional research with a larger sample and greater gender representation is warranted to replicate the present findings. Participant attrition was also high in the present study. However, the two additional analyses carried out (results based on complete cases and using multiple imputation) add to the validity of the identified indirect model. Moreover, given that physical activity and self-esteem were assessed at the same time point, we cannot speak to the causal nature of their association. Indeed, while the practice of physical activity is linked to better self-esteem, the opposite may also true: young people with higher self-esteem could be more likely to engage in physical activity. We also know that adolescents with good mental health are more likely to engage in physical activity, supporting the idea of a bidirectional relationship between physical activity and mental health (56). The present findings must therefore be interpreted with caution and within the scope of the study's design. Nevertheless, the findings highlight how physical activity and self-esteem are related to psychological distress, with physical activity influencing distress indirectly through self-esteem.

To conclude, while this study was conducted during the COVID-19 pandemic, findings are relevant beyond this scope as lessons learned can be reinvested in a host of other potential situations of adversity faced by young people (e.g., school violence, family displacement due to natural disasters, etc.) to ensure their psychological well-being. For instance, schools and community centers should encourage youth engagement in physical activity as it is beneficial for physical and psychological health, in both the short and longer term. Decision makers should also invest in providing youth with green spaces to promote outdoor activities, should future social distancing measures be implemented.