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This review is the result of a virtual, collaborative live review discussion organized and hosted by PREreview as part of the PREreview Champions Program 2025 on April 9, 2025. The discussion was joined by 6 people: 3 facilitators and 3 members of the PREreview 2025 Champions Program cohort. We thank all participants who contributed to the discussion and made it possible for us to provide feedback on this preprint. The authors of this review have dedicated additional asynchronous time over the course of three weeks to help compose this final report using the notes from the Live Review. 

Summary

The study aimed to investigate the effectiveness of physical activity (PA) in mitigating depression and stress in the Brazilian population during different phases of COVID-19 pandemic, while also examining sociodemographic influences. Using a longitudinal approach, the researchers administered online questionnaires to the same cohort at two time points during the peak of lockdown and post-lockdown. Generalized linear model of regression and odds ratio were employed to assess changes in mental health risks. The findings revealed that depression and anxiety risks were higher during the peak of the pandemic period compared to post-lockdown, with individuals engaging in lower physical activity showing the greatest increase in mental health risks over time. Women exhibited higher baseline risks for all three conditions, though odds ratios did not significantly differ for men. A key strength of the study was its repeated measures design, allowing for direct comparison across pandemic phases. However, the limitations include potential sampling bias due to participant attrition between surveys and reliance on self-reported online data, which may introduce recency and trust biases. This study underscores the potential of PA as a mental health intervention while highlighting the need for further research on sociodemographic disparities.

List of major concerns and feedback

The manuscript presents several methodological and analytical areas for improvement that require attention. 

• The absence of p-values for significant determinants limits the interpretation of results, although confidence intervals (CIs) may be sufficient.

• The reviewers recommend applying tests such as the Student's t-test to compare mean differences in anxiety, depression, and stress between periods, after verifying normality.

• The sample overrepresents university- educated individuals, women, and the younger population, limiting generalizability to the broader brazilian population.

• The reliance on online questionnaires excludes those without internet access, introducing selection bias.

• Although the code is available, the language of the survey is not specified, nor is the questionnaire attached in the appendix, both of which are crucial for replicating the study

• The study does not formally test PA as a mediator between pandemic phases and mental health outcomes.

• Including graphs and figures illustrating PA as a mediating factor could be useful in summarizing the effect of physical activity overall.

List of minor concerns and feedback

• No graphs illustrate key relationships (e.g., to illustrate the mediating role of physical activity in depression) making the results harder to interpret. 

• Although the limitations of online sampling in the context of COVID-19 are mentioned, it would be valuable to attach the consent form and clarify in the abstract that "PA" refers to physical activity

• The title implies the findings apply to all Brazilians, but the sample is non-representative 

• No summary statistics (mean, SD) for mental health score for T1 and T2 groups 

• It is recommended to include comparative figures between T1 and T2, as well as data distributions. 

• Finally, it is suggested to moderate statements regarding external factors (e.g., government management) with stronger bibliographic support.

We thank the authors of the preprint for posting their work openly for feedback. We also thank all participants of the Live Review call for their time and for engaging in the lively discussion that generated this review.

Competing interests

The authors declare that they have no competing interests.