Inadequate lumbar protection with load weight limits based on body weight percentages: An experimental and simulation study of the weight limits set by the Japanese guidelines for preventing low back pain

Fuyuki Oyama; Tanghuizi Du; Kazuyuki Iwakiri

doi:10.1371/journal.pone.0327175

Peer Review History

Original SubmissionFebruary 25, 2025
Decision Letter - Massimo Brambilla, Editor PONE-D-25-08962Inadequate lumbar protection with load weight limits based on body weight percentages: An experimental and simulation study of the weight limits set by the Japanese guidelines for preventing low back painPLOS ONE Dear Dr. Oyama, 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. Both reviewers found the manuscript technically sound, with a clear structure, appropriate statistical analyses, and well-reported data. The study is notable for demonstrating that current guidelines may not provide sufficient lumbar protection, making it a relevant and timely contribution to the field. However, the manuscript requires important revisions before publication, focusing on the clarity of the results, expanded discussion, improvement of the conclusion, and emphasis on key findings. Specifically: The presentation of results needs to be clearer, particularly by adding summary tables. The discussion section should go beyond simply restating the results. It needs to offer more analytical depth and clearer implications for guideline development. The conclusion currently does not provide critical reflection and needs improved articulation of the significance of the study, suggesting possible future directions. The authors should emphasise the central finding that weight limits based solely on body weight percentages do not adequately prevent lumbar strain. Given these points, the manuscript must undergo major revisions, addressing all reviewer comments. Please submit your revised manuscript by May 29 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'. 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Kind regards, Massimo Brambilla, Ph.D. Academic Editor PLOS ONE Journal Requirements: 1. When submitting your revision, we need you to address these additional requirements. 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. Thank you for stating the following in the Acknowledgments Section of your manuscript: [This study was supported by the National Institute of Occupational Safety and Health, Japan (N-P03-01). The authors would like to express their gratitude to Junko Fujita, Itoyo Komori, Maki Inoue, and Shuntaro Nakauchi for their assistance with the experiments and data analysis.] We note that you have provided funding information that is not currently declared in your Funding Statement. However, funding information should not appear in the Acknowledgments 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 and let us know how you would like to update your Funding Statement. Currently, your Funding Statement reads as follows: “This study was supported by the National Institute of Occupational Safety and Health, Japan (N-P03-01). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.” Please include your amended statements within your cover letter; we will change the online submission form on your behalf. [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: Yes ****** 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: Yes ****** 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: Yes ****** 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: The manuscript is well organized, but some minor revisions are needed: Lines 45-47: the values given refer to the best conditions for manual handling of loads. It is appropriate to specify this in the text. Lines 56-60: perhaps the frequency of movements and the duration of the tasks are not considered either? If so, it is appropriate to specify this. Lines 102-103: it is necessary to add more information regarding the ease of gripping the load: were there handles or not? It would be useful to add a photo or a figure. Lines 330-331: the frequency of movements and the duration of the task were not considered either (factors that certainly influence the risk). Reviewer #2: Japanese guidelines recommend that the load weight of manual handling should not exceed 40% of the body weight for males and 24% for females. The aim of the study was to identify potential shortcomings of the method of determining load weight limits based on body weight. Here is my comment about it. Methods: In general a graphical representation of the various positions to be performed by the participants could help the understanding of the experimental method that was done. As well as a graphical description of the 3d motion analysis could be useful. Results: lines 223-268: a summary table could improve the understanding of the results. Discussion: lines 271-300: this whole part seems like a repetition of the results. Give more support for the design of new guidelines that really prevent the problem of low back pain. Conclusion: The conclusions lack critical sense of the work and future developments are absent. ****** 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: Yes: Massimo Cecchini 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. https://doi.org/10.1371/journal.pone.0327175.r001
Revision 1
8 May 2025 Author Response Academic Editor: Thank you for considering our submission. Below are point-by-point responses to the issues that were raised. 1. The presentation of results needs to be clearer, particularly by adding summary tables. -> We have added a summary table (Table 4) to enhance the clarity of the presented results. 2. The discussion section should go beyond simply restating the results. It needs to offer more analytical depth and clearer implications for guideline development. -> We have reorganized the Discussion section and included a description of future guideline development incorporating the experimental findings. 3. The conclusion currently does not provide critical reflection and needs improved articulation of the significance of the study, suggesting possible future directions. -> We have revised the Conclusion section to clearly state the key findings that address the objectives of this study. Additionally, we have added a description of future directions. 4. The authors should emphasise the central finding that weight limits based solely on body weight percentages do not adequately prevent lumbar strain. -> We have revised the Conclusion section and emphasized the key finding that load weight limits based on body weight percentages are inadequate for lumbar protection. Reviewer #1: Thank you for reviewing our manuscript. Below are the responses to the comments. 1. Lines 45-47: the values given refer to the best conditions for manual handling of loads. It is appropriate to specify this in the text. -> We have revised the description of the International Organization for Standardization (ISO) guidelines and clarified that the values are “the maximum recommended load weight under optimal conditions” (Lines 44–45). 2. Lines 56-60: perhaps the frequency of movements and the duration of the tasks are not considered either? If so, it is appropriate to specify this. -> The Ministry of Health, Labor and Welfare of Japan (MHLW) guidelines do not set load weight limits based on load handling positions, frequency of movements, or duration of tasks. We have revised the description of the MHLW guidelines (Lines 57–60). 3. Lines 102-103: it is necessary to add more information regarding the ease of gripping the load: were there handles or not? It would be useful to add a photo or a figure. -> As mentioned in lines 102–103, the load was a container with handles on both sides. We have added Fig 2, which shows the container and metal weights. 4. Lines 330-331: the frequency of movements and the duration of the task were not considered either (factors that certainly influence the risk). -> We have clarified that the frequency of movements and duration of the task were not considered for the weight limits and included these factors in the paragraph where the shortcomings of MHLW guidelines are discussed (Lines 310–313). Reviewer #2: Thank you for reviewing our manuscript. Below are the responses to the comments. 1. Methods: In general a graphical representation of the various positions to be performed by the participants could help the understanding of the experimental method that was done. As well as a graphical description of the 3d motion analysis could be useful. -> We have added Fig 3, which shows various positions performed by the participants and examples of the captured motion data (Lines 125–128). 2. Results: lines 223-268: a summary table could improve the understanding of the results. -> We have added ANOVA summary tables (Table 4) and removed the numerical description of the ANOVA results from the main text (Lines 222–264). 3. Discussion: lines 271-300: this whole part seems like a repetition of the results. Give more support for the design of new guidelines that really prevent the problem of low back pain. -> We have removed this part and provided more support for the future development of new guidelines (Lines 314–342). 4. Conclusion: The conclusions lack critical sense of the work and future developments are absent. -> We have highlighted the valuable insights gained from this study in the first paragraph of the Conclusion section (Lines 356–363). Additionally, we have included descriptions for future development in the second paragraph (Lines 364–369). Attachments Attachment Submitted filename: R1response.docx https://doi.org/10.1371/journal.pone.0327175.r002
Decision Letter - Woo-Keun Kwon, Editor PONE-D-25-08962R1Inadequate lumbar protection with load weight limits based on body weight percentages: an experimental and simulation study of the weight limits set by the Japanese guidelines for preventing low back painPLOS ONE Dear Dr. Oyama, 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 Jun 29 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, Woo-Keun Kwon Academic Editor PLOS ONE Journal Requirements: Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice. Additional Editor Comments: Dear Authors, Thank you for the opportunity to review your revised manuscript titled "Inadequate lumbar protection with load weight limits based on body weight percentages: an experimental and simulation study of the weight limits set by the Japanese guidelines for preventing low back pain." I commend the clarity of your analyses and the important contribution this study makes to occupational health and ergonomics. Your findings provide convincing evidence that body weight–based load limits may not offer sufficient protection against lumbar strain, particularly under varied postural and lifting conditions. The integration of biomechanical simulation with task-specific data is a clear strength of this work. That said, I believe the manuscript would benefit from a more thorough treatment of its methodological and contextual limitations. Specifically, I suggest adding a clearly labeled “Limitations” section (or expanding the existing discussion) to address the following points: The use of uniform motion capture data across simulated body weights, which may not reflect actual kinematic variations. The omission of task duration and frequency—factors known to influence low back pain risk. The application of a fixed 3400 N IVD-CF threshold, despite known individual variability in lumbar spine tolerance. The limited generalizability of the findings beyond the Japanese working population. The practical challenges of implementing alternative guideline methods, and the absence of a proposed framework tailored to Japan. Acknowledging these issues directly will enhance the interpretability, rigor, and credibility of your study. I believe these additions will strengthen the manuscript and support its value to both researchers and policymakers. Sincerely, [Note: HTML markup is below. Please do not edit.] Reviewers' comments: Reviewer's Responses to Questions Comments to the Author 1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation. Reviewer #1: All comments have been addressed ******** 2. 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 ****** 3. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: Yes ****** 4. 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 ****** 5. 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 ****** 6. 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: The authors have submitted a revised version of the article, highlighting the changes made in response to the reviewers' suggestions. All comments have been addressed. The article can now be published. ****** 7. 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: Yes: Massimo Cecchini ******** [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. https://doi.org/10.1371/journal.pone.0327175.r003
Revision 2
4 Jun 2025 Author Response Academic Editor: Thank you for considering our submission. Below are the responses to the issues that were raised. 1. That said, I believe the manuscript would benefit from a more thorough treatment of its methodological and contextual limitations. Specifically, I suggest adding a clearly labeled “Limitations” section (or expanding the existing discussion) to address the following points: • The use of uniform motion capture data across simulated body weights, which may not reflect actual kinematic variations. • The omission of task duration and frequency—factors known to influence low back pain risk. • The application of a fixed 3400 N IVD-CF threshold, despite known individual variability in lumbar spine tolerance. • The limited generalizability of the findings beyond the Japanese working population. • The practical challenges of implementing alternative guideline methods, and the absence of a proposed framework tailored to Japan. Acknowledging these issues directly will enhance the interpretability, rigor, and credibility of your study. I believe these additions will strengthen the manuscript and support its value to both researchers and policymakers. → In response to your comments, we have added the relevant limitations to the Discussion section. Journal Requirements: 1. Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice. → We appreciate your bringing the inaccuracies in our reference list to our attention. In response, we have conducted a thorough review to ensure that all references are accurate and complete. We have also verified that no retracted publications are included. Furthermore, we have made the following revisions to the citations: [3]: Replaced the URL to directly link to the cited document file. [5]: Corrected the country name from “England” to “United Kingdom”. [6]: Replaced the citation with the book titled “2023 TLVs and BEIs”. [19]: Added “(in Japanese)” to the end of the title, replaced the URL to directly link to the cited document file, and included the access date. Attachments Attachment Submitted filename: R2response.docx https://doi.org/10.1371/journal.pone.0327175.r004
Decision Letter - Woo-Keun Kwon, Editor Inadequate lumbar protection with load weight limits based on body weight percentages: an experimental and simulation study of the weight limits set by the Japanese guidelines for preventing low back pain PONE-D-25-08962R2 Dear Dr. %Fuyuki Oyama%, 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. If you have any questions relating to publication charges, please contact our Author Billing department directly at authorbilling@plos.org. 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, Woo-Keun Kwon Academic Editor PLOS ONE Additional Editor Comments (optional): As a handling editor of this manuscript, I have carefully examined your revised submission and found that you have sincerely and thoroughly addressed all the comments and suggestions provided in the previous review. Your thoughtful revisions have significantly enhanced the clarity, scientific rigor, and overall quality of the manuscript. I appreciate your diligence and responsiveness throughout the review process, and I am confident that your work will make a valuable contribution to the literature and be of interest to our readers. Reviewers' comments: https://doi.org/10.1371/journal.pone.0327175.r005
Formally Accepted
Acceptance Letter - Woo-Keun Kwon, Editor PONE-D-25-08962R2 PLOS ONE Dear Dr. Oyama, I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now being handed over to our production team. At this stage, our production department will prepare your paper for publication. This includes ensuring the following: * All references, tables, and figures are properly cited * All relevant supporting information is included in the manuscript submission, * There are no issues that prevent the paper from being properly typeset You will receive further instructions from the production team, including instructions on how to review your proof when it is ready. Please keep in mind that we are working through a large volume of accepted articles, so please give us a few days to review your paper and let you know the next and final steps. Lastly, if your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. 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. If we can help with anything else, please email us at customercare@plos.org. Thank you for submitting your work to PLOS ONE and supporting open access. Kind regards, PLOS ONE Editorial Office Staff on behalf of Dr. Woo-Keun Kwon Academic Editor PLOS ONE https://doi.org/10.1371/journal.pone.0327175.r006

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