PONE-D-25-34585Factors contributing to differences in physical activity levels in (pre)frail older adults living in rural areas of ChinaPLOS ONE

Dear Dr. Zhang,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by Oct 07 2025 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Hidetaka Hamasaki

Academic Editor

PLOS ONE

Journal Requirements:

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf

2. Your ethics statement should only appear in the Methods section of your manuscript. If your ethics statement is written in any section besides the Methods, please move it to the Methods section and delete it from any other section. Please ensure that your ethics statement is included in your manuscript, as the ethics statement entered into the online submission form will not be published alongside your manuscript.

3. In the online submission form, you indicated that data cannot be shared publicly because of ethical consideration. Data are available from the corresponding author Institutional Data Access / Ethics Committee for researchers who meet the criteria for access to confidential data.

All PLOS journals now require all data underlying the findings described in their manuscript to be freely available to other researchers, either 1. In a public repository, 2. Within the manuscript itself, or 3. Uploaded as supplementary information.

This policy applies to all data except where public deposition would breach compliance with the protocol approved by your research ethics board. If your data cannot be made publicly available for ethical or legal reasons (e.g., public availability would compromise patient privacy), please explain your reasons on resubmission and your exemption request will be escalated for approval.

4. We note that the grant information you provided in the ‘Funding Information’ and ‘Financial Disclosure’ sections do not match.

When you resubmit, please ensure that you provide the correct grant numbers for the awards you received for your study in the ‘Funding Information’ section.

5. Please note that funding information should not appear in any section or other areas of your manuscript. We will only publish funding information present in the Funding Statement section of the online submission form. Please remove any funding-related text from the manuscript.

6. If the reviewer comments include a recommendation to cite specific previously published works, please review and evaluate these publications to determine whether they are relevant and should be cited. There is no requirement to cite these works unless the editor has indicated otherwise. 

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: I Don't Know

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: No

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: No

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Introduction:

1.Literature gap justification: The introduction mentions that "it is not yet clear how these factors are related to physical activity levels in pre(frail) older adults especially those living in rural areas." However, could you provide more specific evidence about what aspects of this relationship remain unexplored, given the existing literature on frailty and physical activity?

2.Hypothesis development: The hypothesis states that "self-perceived health will have a major impact on physical activity levels compared to other health-related factors." What theoretical framework or preliminary evidence supports prioritizing self-perceived health over other established predictors like social support or physical performance?

3.Geographic specificity: The introduction emphasizes rural China, but how do the unique characteristics of Northeast China (climate, culture, economic conditions) potentially influence the generalizability of findings to other rural contexts?

Methods

4.Frailty classification consistency: The inclusion criteria require "frailty score >0 according to the Fried Phenotype," but later analysis combines pre-frail and frail participants. How might this heterogeneity within the sample affect the interpretation of physical activity predictors, and should these groups be analyzed separately?

5. IPAQ-SF validity concerns: Given that you acknowledge in the discussion that IPAQ-SF tends to overestimate activity levels with correlations often below acceptable standards, why was this instrument chosen over more objective measures, and how might this limitation affect your primary findings?

6.XGBoost model justification: While you mention XGBoost can handle imbalanced data and non-linear relationships, what specific advantages does this approach offer over traditional logistic regression for this particular research question, especially given the relatively small sample size (n=284)?

Results

7.Class imbalance impact: Despite using class weighting, your model shows 90% specificity but only 63% sensitivity. How does this imbalance affect the practical utility of the model, particularly for identifying individuals who might benefit from physical activity interventions?

8.Feature importance interpretation: The SHAP analysis shows SSRS (social support) as highly influential, but Figure 4 shows considerable overlap between groups. How do you explain this apparent contradiction, and what does this suggest about the model's ability to capture the true relationship?

9. Physical performance paradox: Your results show that even the high physical activity group performed below the 5th percentile for age-matched peers on physical tests. How do you reconcile high self-reported physical activity levels with poor objective physical performance measures?

Discussion

10. Causality concerns: The discussion frequently implies causal relationships (e.g., "self-reported health, social support, and physical activity engagement"), but this is a cross-sectional study. How do you address the potential for reverse causality, where poor physical function might lead to negative health perceptions rather than vice versa?

11.Intervention implications: You suggest "community-based social support programs and structured mobility-enhancing exercises," but given that most participants already met high physical activity levels (despite poor physical performance), what specific interventions would be most appropriate for this population?

12.Methodological limitations: While you acknowledge IPAQ-SF limitations in the discussion, this appears to be a fundamental flaw that may compromise the study's validity. How significantly might measurement error affect your conclusions, and should this limitation be addressed more prominently earlier in the manuscript?

Reviewer #2: This manuscript describes the study of factors contributing to differences in physical activity levels in prefrail older adults in rural areas This is an important topic since frailty prevention in older adults should be a priority in all populations.

General comments:

- Authors should follow financial disclosure guidelines.

- Language revision is required.

- Authors declared all data are available without restrictions, yet they later stated that data cannot be shared publicly. Non-identifiable data can be provided without restrictions, and the statements need to be congruent.

Abstract:

- Abstract sections do not usually include a discussion, instead; they include a conclusion. Please follow Plos One guidelines.

Introduction:

- I am not sure how the Chinese government classifies age groups. Is the definition of older adults starts at the age 60 or 65? The authors included patients who were 60 or above. Yet, in the introduction, the classification states 65 years or above. Please explain why you chose to use the age 60 or more instead of official classification.

- Aim: Authors intended to measure the influence of different health domains on physical activity levels. Since this was a cross-sectional study, causality cannot be proven. All we can confirm here is the presence of an association. I would assume that higher physical activity can positively influence other health domains. This is more logically proven via studies on the positive influences of higher physical activity on many health-related aspects and on diseases.

Methods:

- Including all those with Fried’s criteria scores more than 0 means including patients with frailty as well.

- Please provide the approval to use MMSE as it is copy righted.

- Authors included anxiety, depression and social support under perceived health item in the results. Psychiatric problems are not the only contributors to health and not including physical problems as well can gravely affect the results. Please include other aspects of health in your analysis.

Results:

- Where are the supporting tables? I was not able to find them.

- In table 1: authors did not put the significance of all items. Only significant variables had their p values in the table. Please add all the data in the table.

Discussion:

- Please cite the authors by name when it is part of the sentence structure (Page 25 line 324).

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

**********

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

Factors contributing to differences in physical activity levels in (pre)frail older adults living in rural areas of China

PONE-D-25-34585R1

Dear Dr. Zhang,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice will be generated when your article is formally accepted. Please note, if your institution has a publishing partnership with PLOS and your article meets the relevant criteria, all or part of your publication costs will be covered. Please make sure your user information is up-to-date by logging into Editorial Manager at Editorial Manager® and clicking the ‘Update My Information' link at the top of the page. For questions related to billing, please contact billing support.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Hidetaka Hamasaki

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Thank you for submitting the revised manuscript.

Since there has been no response from the two reviewers, I have checked your responses to the reviewers as the Academic Editor on their behalf. It appears that you have provided careful and detailed replies to the reviewers’ comments and suggestions. Appropriate revisions have also been made to the main text and tables, and I believe the manuscript meets the publication standard.

Reviewers' comments: