Skeletal Muscle Ultrasonography and Muscle Fitness Relationships: Effects of Scanning Plane and Echogenicity Correction

Round 1

Reviewer 1 Report (Previous Reviewer 2)

The authors satisfactorily addressed all my comments.

Author Response

Reviewer 1:

 

Reviewer Comment: The authors satisfactorily addressed all my comments.

 

Author’s Response: Thank you for your comments regarding our paper, we feel the changes improved the manuscript.

Reviewer 2 Report (New Reviewer)

Dear Authors

As one of the reviewers, I express my personal scientific opinion on your work. I would like to reassure you that I was trying to be positive and constructive but particularly as fair and honest to your work.

The clear explanation provided in Methods section is appreciated. I should also note that the originality of the study (i.e. using relatively sophisticated/modern tools/instrumentation and assessment methods such as transverse MT and Sagittal EI evaluations), the statistical approach and the simple but clear work done on table and figures are all constructive/positive points. Yet, the lack of test-retest reliability and/or intra-class correlation coefficient (ICC) and the confident intervals (CI) are somewhat negative points.

Please accept my judgment with a positive and constructive way.

1.       What about test-retest reliability and/or ICC and CI of your tests, tools and devices, particularly for particularly for evaluating transverse MT and Sagittal EI? If you have these results please provide them.

2.       Abstract, line 10: What is actually the EI? Please abbreviate beforehand.

3.       Line 38: The same as before.

4.       Lines 203-204: echo intensity or EI?

5.       Lines 211-213 - You are giving the following clarification: “The differences in findings in the current study may relate to the inclusion of habitually resistance-trained individuals, rather than older or untrained populations”. Based on this particular clarification, if your study included very well or elite resistance-trained participants would you expect different results?

Comments for author File: Comments.pdf

Author Response

Reviewer Comment: What about test-retest reliability and/or ICC and CI of your tests, tools and devices, particularly for particularly for evaluating transverse MT and Sagittal EI? If you have these results please provide them.

Author’s Response: Thank you for your comment regarding the test-retest reliability of the methods and tools of our paper. The research group responsible for the current manuscript has published their test-retest reliability statistics in the Journal of Functional and Morphological Kinesiology (Carr et al. 2021; DOI:  10.3390/jfmk6040091). This paper examines similar ultrasonography techniques by the same researchers, and performed ultrasonography analysis in a similar manner. 

Reviewer Comment: Abstract, line 10: What is actually the EI? Please abbreviate beforehand.

 

Author’s Response: Thank you for noticing this oversight. The term ‘echo intensity’ has been added to the abstract before the term EI.

 

Reviewer Comment: The same as before.

 

Author’s Response: Thank you for noticing this oversight. The term ‘echo intensity’ has been added to the abstract before the term EI.

 

Reviewer Comment: Lines 203-204: echo intensity or EI?

 

Author’s Response: The term echo intensity and EI are synonymous in the paper. EI is the contraction of echo intensity, and thus the use of ‘EI’ in lines 203-204 is correct.

 

Reviewer Comment: Lines 211-213 - You are giving the following clarification: “The differences in findings in the current study may relate to the inclusion of habitually resistance-trained individuals, rather than older or untrained populations”. Based on this particular clarification, if your study included very well or elite resistance-trained participants would you expect different results?

 

Author’s Response: Thank you for your comment regarding training status. We would expect similar results in a very well or elite resistance trained population, as the lowest level of training experience in our study was habitually resistance trained. As outlined in our participants section, the sample included collegiate, competitive, and national competition level athletes. These athletes are considered in the upper-echelon of their respective sports and have qualified for national rankings. As our data is normally distributed, the elite athletes measurements fall within the overall results of the study.

 

The changes to the manuscript are attatched below.

Author Response File: Author Response.docx

Reviewer 3 Report (New Reviewer)

thank you this a good piece of work

where I struggle is the size and nature of your sample. it seems very specific to a sample of younger adults yet you extrapolate that to ' an 'older' population. what is the relevance of this

there is a section failing in that methods comes at the end

there is poor definition as to what is meant by 'habitual' throughout the submission 

whilst the correlations may be significant are they relevant

I have attached a file with comments

 

 

 

Hope this helps

Danny 

 

 

Comments for author File: Comments.pdf

Author Response

Reviewer Comment: where I struggle is the size and nature of your sample. it seems very specific to a sample of younger adults yet you extrapolate that to ' an 'older' population. what is the relevance of this

Author’s Response: Thank you for your comments regarding the sample and generalization of this information to other population. In the manuscript, we talk about older populations in an attempt to provide context. Specifically, in line 56, we mention the weak to moderate correlations of echo intensity and gait speed. This is mentioned to examine where and how echo intensity is used in literature, noting that the measure has undefined significance and use. We then mention the older populations in line 210 to note that this population is habitually resistance trained, and that our findings are differing that the older or untrained populations observed in literature. Our only specific mention of generalization of this sample to older adults is in line 235, wherein our aim was to mention the limitation of doing so.

Reviewer Comment: there is a section failing in that methods comes at the end

Author’s Response: Thank you for your comments regarding the structure of the draft. The authors utilized a template obtained from Muscles wherein the order is labeled as: Introduction, Results, Discussion, and Methods. Due to this, we want to respectfully maintain the structure as instructed by Muscles.

Reviewer Comment: there is poor definition as to what is meant by 'habitual' throughout the submission 

Author’s Response: Thank you for your comment regarding the training status of the participants. We chose to use the term ‘habitual’ as each participant has undergone years of structured resistance training. While some participants performed at national and collegiate levels within their respective sports, habitual resistance training encompasses their approach to training. The term ‘habitual’ has now been defined in the manuscript in the participants section on line 286-288 as ‘The resistance training experience demonstrated by each participant qualifies as habitual training, following a structured exercise protocol for an extended period of time.’, per your suggestion.

Reviewer Comment: whilst the correlations may be significant are they relevant

Author’s Response: Thank you for the comment regarding the relevancy of the correlations. The variables and measures in the current study are relevant to the current literature in addition to traditional resistance training. Ultrasonography variables in the manuscript such as muscle size and scanning plane are commonly used in research, while the work done regarding methodological approaches provides novel and relevant information for researchers. Additionally, the resistance training variables of 1 repetition maximum strength and local muscle endurance are directly relevant to current research and traditional resistance training. Correlating the ultrasonography and resistance training variables provides relevant information for future studies examining the relationship of muscle size and quality with performance.

Reviewer Comment:  I have attached a file with comments

Author’s Response: Thank you for the line-by-line edits to our manuscript. We have addressed each of these concerns and additions are denoted by a highlight while removals are denoted by a strikethrough.

 

The updated manuscript is attatched below containing the changes. 

Author Response File: Author Response.pdf

Reviewer 4 Report (New Reviewer)

The manuscript by Voskuil C. et al examines the relationships between ultrasonography measured muscle size and echo intensity (EI) with muscle strength and endurance. The muscle size and echo intensity were measured by three different ultrasonography imaging strategies in the sagittal view, transverse view, and extended field of view. The calculated Pearson correlation coefficients between muscle size with either muscle strength or muscle endurance are consistent in all three strategies. Though there are no correlations between EI and muscle strength and endurance by Pearson correlation, there are indeed consistent correlations between corrected EI and muscle strength and endurance. Overall, the study is well designed, and the correlations between muscle size and echo intensity (EI) with muscle fitness are informative for practical and clinical settings. I have a few minor comments that need to be addressed.

Line 14, line 38, EI (EI) should be corrected to echo intensity (EI).

Figure 1, using lowercase r for Pearson correlation.

Discussion, in many descriptions, EI and cEI are not correctly referred to as what they truly mean. For example, at line 206, line 255, EI should be corrected to cEI.

Figure 2, no dashed line in the figure, though it was mentioned in the legend.

Author Response

Reviewer Comment: Line 14, line 38, EI (EI) should be corrected to echo intensity (EI).

Author’s Response: We have updated the abstract (line 14) to correctly denote EI and the introduction (line 38) to define echo intensity before the use of the term EI. Thank you.

Reviewer Comment: Figure 1, using lowercase r for Pearson correlation.

Author’s Response: Thank you for your comment on the correct use of ‘r’ for Pearson Correlation. We have updated Figure 1 to ‘r’ rather than ‘R’.

Reviewer Comment: Discussion, in many descriptions, EI and cEI are not correctly referred to as what they truly mean. For example, at line 206, line 255, EI should be corrected to cEI.

Author’s Response: Thank you for your clarification comments on EI and cEI. In the introduction, line 74-75, we have added the term ‘adipose tissue corrected echo intensity (cEI)’ to provide correct context for cEI in the paper. In the first location (line 206), the use of EI is chosen as it is the measure of echo intensity. In line 255, it again is used to denote the use of echo intensity must cautioned and the use of cEI should be considered. In the manuscript, EI was not correlated with muscle strength or local muscle endurance, while cEI did demonstrate relationships. We respectfully ask to keep the terms as they are, with the clarification of cEI denoted in the introduction to aid in the understanding and ease of reading.

Reviewer Comment: Figure 2, no dashed line in the figure, though it was mentioned in the legend.

Author’s Response: Thank you for the comment regarding figure 2. The dashed line in figure 2 is vertical on the bicep, directly perpendicular to the solid line (left image in figure 2). There may have been confusion in the legend due to the dashed line referring to the left image, while the solid line was stated to refer to the right image. We have updated the legend for both the solid and dashed line to refer to the left image.

 

The changes to the manuscript have been identified and attatched below. 

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report (New Reviewer)

this is good work. I am still confused as to why the methods is the final section but if that is the journal format then so be it. I have no other comments to add. Well done.

Danny

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

This study tried to explain the relationship between muscle morphology in strength and endurance in biceps curl using athletes. The work is interesting and can help to other researchers that are working in ultrasound imaging and exercise, in addition, the analysed variables were well selected. Although this, the manuscript has a very worrying and bad elaboration and structure. Additionally, there are several important flaws that can influence in the clearness, the reproducibility and transferability.

 

 - Line 13- Define the abbreviations in the abstract previously please.

 

- The manuscript is not well ordered. After the background, the Results section appears. Please, restructure properly the draft.

 

- Please, include pictures about the placement of the transducer over the skin and examples of how you took the region of interest in an ultrasound image.

 

- Echo-intensity analysis can be influenced due to region of interest size. How can you solve or reduce this problem?

 

- Line 319 and 130- Typo: “biceps” not “bicep”

 

The Discussion section is also unstructured properly. Limitations is not at the end; the Strengths paragraph is repeating the results. Please, restructe and improve this section.

 

- In addition, the authors do not describe clearly how these features will be evaluated clinically or in a sport context to personalize management or assessment in athletes.

 

- In Statistics Analysis part, authors talked about some statistics, "distances", and correlations that readers cannot understand. These parts need more clearly description about all the process and more reference to base the analysis.

 

- Important information is missing that would facilitate reproducibility of the study, including software version of the ultrasound scanner.

 

- In the regression analysis, the authors ignored important demographic information to complete the analysis like physical activity level, age, BMI, weight, ethnicity. These results are very difficult to transfer to a real environment.

 

- The evaluator was blinded? Please, mention something about it.

 

- Line 172- “Lastly, we are unable to determine whether ultrasound image acquisition or analyses explains our findings as they show a unique influence on image outcomes”

How can readers can interpret this? Please, give more details about this statement.

Reviewer 2 Report

The manuscript is interesting, well prepared and has merit, I only have a few comments:

1.     The figures should be self-explanatory. Please provide explanations for all abbreviations used in the figure captions to improve clarity for the reader.

2.     Since the figures and tables present the same data, it may be more effective to move the figures to the supplementary material. Additionally, consider including other relevant scatter plots in the supplementary material to provide a more comprehensive overview of the data.

3.     To further enhance the manuscript, please include representative US images of the biceps muscle in both planes.

4.     It would be helpful to provide information on how the images were exported, whether raw images were analyzed, and what format the images were in.

5.     To improve the organization and clarity of the manuscript, please move the appendix to the supplementary material.

6.     To improve the flow of the manuscript, the data on the study participants should be presented in the results section.

7.     Please ensure that it is clearly stated in the abstract that this study included only healthy young adults and that elderly, obese individuals, or those taking medications or suffering from chronic illnesses were not included in the study.

Reviewer 3 Report

This study reveals the relationship between skeletal muscle morphological characteristics and the muscle strength using ultrasound imaging, and the results shown indicate the potential of ultrasound imaging for functional assessment of skeletal muscles. However, this study has serious faults.

 

(1) The present study does not indicate any data on non-trained subjects as a control group. Therefore, it is impossible to properly evaluate whether the results shown for the resistance training group are really due to the effects of resistance training. The data for the non-trained subjects must always be indicated as a control group.

 

(2) In this study, data are analyzed using several statistical methods. Therefore, the adequacy of the sample size should be indicated.

 

(3) In this paper, the explanations for figure 1 and 2 are not provided anywhere in the paper. Therefore, it is difficult to properly examine this entire paper, including the discussion section.