Locomotion control during curb descent: Bilateral ground reaction variables covary consistently during the double support phase regardless of future foot placement constraints

Chuyi Cui; Ashwini Kulkarni; Shirley Rietdyk; Satyajit Ambike

doi:10.1371/journal.pone.0268090

Peer Review History

Original SubmissionApril 20, 2022
2 Sep 2022 Decision Letter - Hugh Cowley, Editor PONE-D-22-11648Locomotion control during curb descent: Bilateral ground reaction variables covary consistently during the double support phase regardless of future foot placement constraintsPLOS ONE Dear Dr. Ambike, 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 see the reviewers' comments below. Please note that while Reviewer #2 was quite critical regarding the overall significance of this study compared to previous work in the field, and we respect that opinion, it is our assessment that this does not fail our criteria for publication; novelty (in the sense of significance or impact) is not a requirement for publication in PLOS ONE for original research that otherwise meets our requirements for quality of execution, reporting, and ethical standards. As such, while you may wish to clarify the specific contributions this work brings to the field, we require you only to address the other comments raised by each reviewer. Please submit your revised manuscript by Oct 17 2022 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. 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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. We note that you have stated that you will provide repository information for your data at acceptance. Should your manuscript be accepted for publication, we will hold it until you provide the relevant accession numbers or DOIs necessary to access your data. If you wish to make changes to your Data Availability statement, please describe these changes in your cover letter and we will update your Data Availability statement to reflect the information you provide. 3. 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. [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: Thank you for this well-written and interesting paper. Also, your description of UCM was well done-- terse but complete. I have two comments for things that you need to address before publication: 1) where is the "foot center" line 170 p8 and throughout. Specifically, how do you define the foot center? I can imagine that the target center is the geometric center of the box. Obviously, this is a critical component of your results. 2) Were you participants shod or unshod? Please specify and if shod, discuss what kind of shoes and how that might have effected the results. Reviewer #2: The paper is an extension of the “synergy index” line of work on which Dr. Ambike has developed and published extensively. The current focus is whether a targeted stepping requirement subsequent to a step up or down on a curb influence the synergy indices during the “curb step” compared to a condition in which no targeted stepping is required. The results showed minor effects, primarily in gait parameters, of the targeted stepping task. The authors conclude that performance on the targeting task had “low cost” relative to the task of maintaining upright stability while stepping up or down. Therefore, the targeting task had little effect on the synergy indices. I agree with the authors’ interpretation of the results. There were small adjustments in gait parameters during the targeting conditions compared to baseline. But clearly, the targeting tasks were not demanding enough to threaten the stability of the upright body while stepping up or down. From this perspective, the paper reproduces many of the results found in previous work, such as synergy indices related to free moments are related to upright stability moreso than ground reaction forces. The attempt to modify this essential finding was not successful. Such results contribute to the synergy index line of work in showing the nervous system prioritizes constraints while moving through the environment. Not a dramatic contribution. Minor Comments 1. P 10 1st PP confusing sentences - please clarify. “All remaining measures included only the trials where the target did not shift. Thus, in the remaining measures, the foot placements during curb descent as well as the next step were the same in every task, and the expectation of a target shift differs across the tasks.” 2. P 10, line 221 – “…the same the ANOVA…” remove “the” before ANOVA. 3. Figure 2 caption – What are “…dissimilar letters…”? ****** 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. https://doi.org/10.1371/journal.pone.0268090.r001
Revision 1
15 Sep 2022 Author Response We thank the reviewers for taking the time to review our manuscript and for their valuable feedback. Below is our point-by-point response to the editor’s comments and then the reviewers’ comments. Editor’s comment: Please note that while Reviewer #2 was quite critical regarding the overall significance of this study compared to previous work in the field, and we respect that opinion, it is our assessment that this does not fail our criteria for publication; novelty (in the sense of significance or impact) is not a requirement for publication in PLOS ONE for original research that otherwise meets our requirements for quality of execution, reporting, and ethical standards. As such, while you may wish to clarify the specific contributions this work brings to the field, we require you only to address the other comments raised by each reviewer. RESPONSE: Thank you for the comment. We respect this comment by Reviewer 2. We have responded to it in this document below. The main contributions of this work are: (1) the robust nature of the synergies, and (2) the replication of the synergy results from our previous work (Cui et al 2018). We think that the point about robust synergies is quite salient – in the title, abstract, discussion and conclusion sections. We adjusted some language to make the point about replication more prominent (Lines 328 - 333). Comments by Reviewer 1: Thank you for this well-written and interesting paper. Also, your description of UCM was well done-- terse but complete. RESPONSE: We thank the reviewer for the encouragement. I have two comments for things that you need to address before publication: 1) where is the "foot center" line 170 p8 and throughout. Specifically, how do you define the foot center? I can imagine that the target center is the geometric center of the box. Obviously, this is a critical component of your results. RESPONSE: Foot center was defined as the average (geometric center) of the digitized toe and heel positions. The foot center was computed only when the foot was fully on the ground. For computing stepping error, the vertical coordinate of the foot center was ignored and only the AP and ML coordinates were utilized. We added text (Lines 173 and 181) to clarify this point. 2) Were you participants shod or unshod? Please specify and if shod, discuss what kind of shoes and how that might have affected the results. RESPONSE: All participants walked with their own shoes. We instructed the participants to wear comfortable athletic shoes to the experiment. Walking in their own shoes adds to the ecological validity of the gait task. Compared to walking over level ground, there is greater impact on the foot while stepping down from a curb, and this may influence behavior. We decided to study shod walking because young adults likely spend more time walking with shoes than without, especially over uneven terrain. We added text in the Methods section (Line 111) to clarify this point. As for the effect of performing our tasks with and without shoes: There would likely only be minor differences across the shod/no-shod condition, if any. Specific values of the outcomes might change, but we expect the same significant effects in our statistical comparisons. There is no good reason why the synergy indices – the focus of this work – would change differently for expectation of shifting targets when wearing shoes versus barefoot. Comments by Reviewer 2: The paper is an extension of the “synergy index” line of work on which Dr. Ambike has developed and published extensively. The current focus is whether a targeted stepping requirement subsequent to a step up or down on a curb influence the synergy indices during the “curb step” compared to a condition in which no targeted stepping is required. The results showed minor effects, primarily in gait parameters, of the targeted stepping task. The authors conclude that performance on the targeting task had “low cost” relative to the task of maintaining upright stability while stepping up or down. Therefore, the targeting task had little effect on the synergy indices. I agree with the authors’ interpretation of the results. There were small adjustments in gait parameters during the targeting conditions compared to baseline. But clearly, the targeting tasks were not demanding enough to threaten the stability of the upright body while stepping up or down. From this perspective, the paper reproduces many of the results found in previous work, such as synergy indices related to free moments are related to upright stability more so than ground reaction forces. The attempt to modify this essential finding was not successful. Such results contribute to the synergy index line of work in showing the nervous system prioritizes constraints while moving through the environment. Not a dramatic contribution. RESPONSE: We respectfully suggest that although not dramatic, the contributions of this work are significant. We show that, at least to the set of expected maneuvers that we used, these synergies are robust. This was not known before. Furthermore, our earlier paper was the first to introduce the UCM analysis of all ground reaction variables. Given the novelty of this analysis, it is quite important to demonstrate the replicability of the results, which we have achieved here. Minor Comments 1. P 10 1st PP confusing sentences - please clarify. “All remaining measures included only the trials where the target did not shift. Thus, in the remaining measures, the foot placements during curb descent as well as the next step were the same in every task, and the expectation of a target shift differs across the tasks.” RESPONSE: By analyzing only the trials where the target did not shift in the Anterior- and Lateral-shift conditions, we are certain that any difference in the outcomes is attributable to only to the expectation of a maneuver. We have expanded the section on how the data were analyzed to improve clarity (Lines 208-214). 2. P 10, line 221 – “…the same the ANOVA…” remove “the” before ANOVA. RESPONSE: Thank you for pointing out the typo. We edited the text as suggested (Line 227). 3. Figure 2 caption – What are “…dissimilar letters…”? RESPONSE: We replaced “dissimilar letters” with “…different letters…” in all the captions (Lines 564, Line 567, Line 574, and Line 585) https://doi.org/10.1371/journal.pone.0268090.r002
19 Sep 2022 Decision Letter - Hugh Cowley, Editor Locomotion control during curb descent: Bilateral ground reaction variables covary consistently during the double support phase regardless of future foot placement constraints PONE-D-22-11648R1 Dear Dr. Ambike, 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 for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, 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, Hugh Cowley Staff Editor PLOS ONE Additional Editor Comments (optional): Reviewers' comments: https://doi.org/10.1371/journal.pone.0268090.r003
Formally Accepted
26 Sep 2022 Acceptance Letter - Hugh Cowley, Editor PONE-D-22-11648R1 Locomotion control during curb descent: Bilateral ground reaction variables covary consistently during the double support phase regardless of future foot placement constraints Dear Dr. Ambike: I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department. 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 plosone@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 Mr Hugh Cowley Staff Editor PLOS ONE https://doi.org/10.1371/journal.pone.0268090.r004

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