Sex-Related Differences of Weight Bearing and Non-Weight Bearing Muscle Properties

Round 1

Reviewer 1 Report

1. Please explain why it did not take place familiarization training for the participants. Can this affect the results? 

2. Please provide the main results in a bar graph.

3. Please provide what <<new>> this study says, and compare it with other studies. 

Author Response

1. Please explain why it did not take place familiarization training for the participants. Can this affect the results? 

*Thank you for asking this. At the time of data collection (Fall 2020), the university was still under strict COVID-19 research protocols. In attempt to limit any potential contact due to additional exposure, the IRB requested the study only include one study visit per subject and to try to minimize time allotted per participant in the laboratory. We also followed the guideline of only 1 other individual in the laboratory space other than the investigator per testing session, thorough cleaning protocols and at least 30 minutes between any 2 participants on the same day. Although we agree that a familiarization session may have been beneficial, the participants all reported having resistance exercise experience and had the opportunity to practice the movements through multiple warm up trials prior to final scores being recorded on the movements. This has been added to the Methods section to be more detailed and as a limitation of the study in the discussion.

2. Please provide the main results in a bar graph.

*Thank you for this suggestion. The main results have been added as figures (bar graphs) for the primary outcome variables. It is a nice depiction of the primary results, yet seems redundant with Table 1. We have also added Table 2 to demonstrate the correlations identified.

3. Please provide what <<new>> this study says and compare it with other studies. 

*Thank you for this comment. The Introduction now includes remarks on the novelty of this study as it develops into the study purpose. Additionally, this is expanded upon in the discussion and how these novel results relate to any existing research in the area. Briefly, even though there has been evidence of the differences of muscle characteristics in males and females, those studies were not utilizing the use of the ultrasound images to evaluate the composition of the muscle. Use of ultrasound as an accurate yet non-invasive measure of muscle size and pennation angle has not been previously utilized in this context. Further, the direct comparison between weight bearing and non-weight bearing has not been made previously. There has been limited evidence of changes in muscle properties of those two groups but no cross-over evaluation of weight-bearing and non-weight bearing muscle characteristics and relationships. These points have been integrated into the discussion.

Reviewer 2 Report

In the manuscript entitled “Sex-Related Differences of Weight Bearing and Non-Weight Bearing Muscle Properties”, the authors employed echo intensity analysis and compare the difference of muscle properties between young males and females. However, I have two major concerns about this manuscript:

1.     Since most of results in this manuscript have been reported by other researchers previously. what’s the major novelty of this manuscript?

2.     How did the authors determine the daily exercise level of the participants in this study? Different exercise level may cause the difference muscle properties.

Author Response

1. Since most of results in this manuscript have been reported by other researchers previously. what’s the major novelty of this manuscript?

*Thank you for this comment as it is similar to that of another reviewer. The Introduction now includes remarks on the novelty of this study as it develops into the study purpose. Additionally, this is expanded upon in the discussion and how these novel results relate to any existing research in the area. Briefly, even though there has been evidence of the differences of muscle characteristics in males and females, those studies were not utilizing the use of the ultrasound images to evaluate the composition of the muscle. Use of ultrasound as an accurate yet non-invasive measure of muscle size and pennation angle has not been previously utilized in this context. Further, the direct comparison between weight bearing and non-weight bearing has not been made previously. There has been limited evidence of changes in muscle properties of those two groups but no cross-over evaluation of weight-bearing and non-weight bearing muscle characteristics and relationships. These points have been integrated into the discussion.

2. How did the authors determine the daily exercise level of the participants in this study? Different exercise level may cause the difference muscle properties.

*Thank you for this comment. Exercise status was self-reported by each participant upon their screening and consent to participate. Each participant filled out a health and exercise status questionnaire where it was determined that each participant had some level of physical activity and experience lifting weights. They were not considered “untrained” because every participant had reported regular participation in aerobic, recreational, and resistance exercise on a weekly basis and had participated in such exercise for at least 6 months prior to participation in this single-visit study.

Reviewer 3 Report

Design and methods of the study should be placed after the introduction as it is the standard procedure and will help readers to follow the manuscript.

English language must be extensively reviewed as sometimes is difficult to understand for the reader. For example, we can see this phrase in the manuscript, "additional independent t-tests indicated similar differences between males and females for the upper limb" which is hard to understand as the authors are comparing males and female  in this study but this phrase indicates that differences are similar between both groups which doesn't really make sense. 

Author Response

-Design and methods of the study should be placed after the introduction as it is the standard procedure and will help readers to follow the manuscript.

-English language must be extensively reviewed as sometimes is difficult to understand for the reader. For example, we can see this phrase in the manuscript, "additional independent t-tests indicated similar differences between males and females for the upper limb" which is hard to understand as the authors are comparing males and female in this study but this phrase indicates that differences are similar between both groups which doesn't really make sense. 

*Thank you to this reviewer for their timely review and insight on our manuscript. In response to your listed comments, we appreciate the remark and agree that the Design and Methods should be presented after the Introduction as most journals require. The reviewer's recommendation would present a better flow and prepare the reader for the specific variables that were assessed and analyzed before the Results are presented. However, we used the recommended template provided by MDPI: Muscles and in their format, the Design and Methods are presented at the end of the manuscript. We hope this is acceptable.

*Additionally, we appreciate your comment that the way the results are written was a bit obscure and confusing for the reader. We have amended the Results to present the findings in a more straightforward/clear manner. Specifically, for the section pointed out by the reviewer, we have reworded the results to state: “

*The authors are native to the US and are primary English speakers and apologize for the original version of the manuscript and our edition of scientific writing was obscure. Again, the manuscript has been amended to reflect more comprehensive, consumable English writing and grammar. We hope you find these modifications sufficient. 

Round 2

Reviewer 1 Report

1. Please provide one type of SD in the graphs. In Figure 1b the graph does not have the line of SD as the other graphs. 

2. Please provide statistical significance r Pearson correlation with a graph. 

Author Response

Muscles R2

We would like to thank the reviewer for their time and diligence in re-reviewing our manuscript. Please fine the updated submission with all included edits. Individual responses to requested changes can be found below and in the provided files.

Reviewer 1

1. Please provide one type of SD in the graphs. In Figure 1b the graph does not have the line of SD as the other graphs. 
   1. Thank you for catching this Figure 1 has been updated where all bars have SD lines.
2. Please provide statistical significance r Pearson correlation with a graph. 
   2. We appreciate this request. It is unclear if the reviewer wants all correlation graphs or only the significant ones? Nevertheless, Correlation graphs have been created for all of the comparisons and added as a supplemental file. The specific correlations with significance are indicated in Table 2. Some of the correlations (r) were initially incorrectly entered and have been updated as well.

Reviewer 2 Report

No other comment.

Author Response

Reviewer 2: No other comment.

*Thank you to the reviewer, for their time and effort in evaluating this manuscript. We understand your time is valuable and appreciate every bit of it.