PONE-D-23-39697Cerebral cortex activation and functional connectivity during low-load resistance training with blood flow restriction: An fNIRS studyPLOS ONE

Dear Dr. Jia,

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 There were significant concerns raised by both reviewers, however, I would like to give you the opportunity to address the concerns. Please make sure you put exact p values and ensure that the discussion of findings aligns with the study design of the present work.

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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: Partly

Reviewer #2: No

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

Reviewer #1: Yes

Reviewer #2: Yes

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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

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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: No

Reviewer #2: Yes

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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: comments uploaded

Title of Article: Cerebral cortex activation and functional connectivity during low-load resistance training with blood flow restriction: An fNIRS study

General Comments: The authors did a nice job presenting the recent literature as the foundation for the research question utilizing fNIRS to evaluate functional connectivity of different brain regions during resistance training under blood flow restriction. The authors highlight the importance of investigating this phenomenon, as there are many mechanisms associated with blood flow restriction training; it is crucial to also evaluate the neurophysiological mechanisms. However, I feel that the paper needs several major changes in order to strengthen the overall paper. The underlying mechanisms associated with CNS activation and FC regarding resistance training should be highlighted much earlier – in the introduction – to allow for a nice framework for the purpose of the study. The lack of a control group to evaluate differences between BFR / non-BFR training greatly affects the strength of any conclusions to be made regarding adaptations or activity. Furthermore, the absence of a limitations section to address any potential factors associated with the paper are concerning. A more thorough review of the manuscript for grammatical errors and sentence structure is needed, as well as limiting causal language when describing findings. The work presented would be a great first experiment for a future experiment that evaluates the FC between groups, in which more appropriate conclusions could be drawn regarding adaptations; even more so if these adaptations could be evaluated after an intervention study utilizing BFR and its influences on FC and “muscle output” during regular resistance training. Overall, I feel that, with these revisions in mind, the final project will be a solid contribution to the literature. The authors should be commended for all their hard work that was put into this project.

Specific Comments: Specific comments related to my aforementioned general comments are noted below.

Introduction

Line 61: be clear throughout the entire manuscript when discussing resistance training v. resistance exercise – it seems later on it is exclusively written as resistance training (RT), so consider changing this here.

Line 64: consider changing to “investigate potential mechanisms”.

Line 65: with the active verb investigate already earlier in the sentence, consider editing sentence structure to “. . . hormone regulation, and other mechanisms at the cellular and molecular level”.

Line 77: throughout the manuscript, the term adaptation is used to explain the findings of increased cerebral cortex activity due to BFR … with no control group to compare to or increase in some index of performance after the implementation of BFR training, is it suitable to characterize this as an adaptation? Consider justifying this (potential mechanisms associated with increased activity) or explain findings as the increased activity of the cerebral cortex (as stated in the title) and allow for future work to evaluate this as a suitable adaptation due to BFR.

Line 88: consider adding “the” when referencing the prior study (17)

Line 106: the intro discussed 1RM intensities between 20-30%, is there a rationale for choosing 30% for this paper?

Lines 108 – 112: consider editing sentence structure for a better understanding and delivery of second hypothesis.

Methods

Line 125: what neurological and psychological disorders were excluded? Consider being more specific here.

Line 183: consider changing “hypothesis” to “hypotheses” as it seems to be referencing the multiple hypotheses of the paper.

Results:

Consider changing the p values that are reported to = 0.00 to < 0.001.

In Table 1, assuming it is due to rounding, it is noted that the second p value of 0.05 is significant … consider making this clearer or reporting the p value that was less than .05.

Discussion

Line 247: the main finding mentions cortical activation not cortical adaptation – this conclusion seems more relevant to the purpose of this experiment and should match the rest of the manuscript when discussing the purpose.

Line 249-252: as stated above, consider laying out the underlying theoretical framework regarding CNS activation earlier in the introduction to emphasize the importance of the investigation.

Line 253: consider changing “liming” to “limits”.

Line 255: edit sentence structure / grammar – what is it meant by cerebral energy supply? Consider reframing this explanation as “cerebral oxygenation” in line with previous references in the manuscript.

Line 257: the referenced article evaluated the activity during index finger contractions … is this applicable to squat movement and associated brain activity? If so, consider mentioning this paper’s methodology / rationale for cortical activity across different muscular movements.

Line 261: what is it meant by the term “muscle output”? is this meant to be force output? Or muscle activity? Motor unit recruitment? Clearly define what this term means to allow for a better link with findings.

Lines 261 – 265: edit grammar and sentence structure.

Line 288: causal language of “confirming” CNS activity with BFR training. Is there not CNS activity with non-BFR training? Consider elaborating on this finding of augmenting CNS activity with BFR, and what future work could evaluate with this in mind.

Line 293: it is highlighted that there is already high FC during RT without BFR, is this from previous research? If so, which articles should be cited? Moreover, the lack of a control condition to evaluate this outcome limits the overall strength of the study.

Line 301: consider changing to “. . . as the metabolic stress within muscles rises with high pressure”.

Line 302: consider changing “needs to” to “must”.

Line 310: instead of “dominate” use “dominant”.

Lines 312 – 314: edit grammar and sentence structure.

Conclusion

I believe the future work listed would greatly benefit the overall paper / project if a follow-up study was conducted evaluating the differences between a BFR and non-BFR condition. If the goal is to evaluate this effect from BFR as an adaptation, consider an intervention study and looking at pre-post CNS activity – could this be beneficial for overall RT? Populations beyond training populations could benefit as well.

Line 323: consider changing to “neurophysiological mechanisms” as there are more than just one.

Reviewer #2: Thank you for the opportunity to review this manuscript. The author sought to investigate the effects of different pressures on cerebral cortex activation and functional connectivity during the squat exercise. While the design of this study is interesting, I have several concerns about the writing and the claims made by the authors. The authors discuss the adaptation that occur from blood flow restriction training however, this study was acute and therefore cannot make such claims.

Please see the specific comments below.

Lines 65-66 “Surprisingly, even though neural adaptation has been a significant contributor to muscle hypertrophy and strength gain (9–11),”

I am not sure the role that neural adaptations have on hypertrophy. I think it would be helpful if the authors could elaborate more.

Lines 69-71 “In addition, a study has shown that muscle hypertrophy can transfer from muscles exposed to BFR to muscles not exposed to BFR (14).”

I am not sure this study measured hypertrophy. Please see doi: 10.1111/j.1475097X.2010.00949.x

Lines 121-123 “The sample size determination was based on prior-power analysis in G*Power and MPower (32,33). More details about the prior power analysis can be found in Supplementary Materials.”

this is not sufficient to replicate your power calculations. The information in the supplemental materials is also insufficient. Please provide further detail on what variable and that parameters were used to estimate sample size.

I also noticed the subject’s anthropometrics were not provided. Please report their height weight and their max strength. I apologize if I missed it.

For the discussion all talk about the adaptations need to be removed as it is not possible to make such claims from an acute study

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Reviewer #1: No

Reviewer #2: No

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Cerebral cortex activation and functional connectivity during low-load resistance training with blood flow restriction: An fNIRS study

PONE-D-23-39697R1

Dear Dr. Jia,

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.

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Kind regards,

Jeremy P Loenneke

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

The only remaining change is to change "between group" to "between condition" since this is a within participant design. That can probably be made in the editing stage.

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

Reviewer #2: All comments have been addressed

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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

Reviewer #2: Yes

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

Reviewer #1: Yes

Reviewer #2: Yes

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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

Reviewer #2: Yes

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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

Reviewer #2: 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: (No Response)

Reviewer #2: That authors have addressed my concerns.

I have one more concern. I must apologize for not catching this earlier. But the authors should change between group to between conditions as this was a within subject design.

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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.

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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

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