All reviews of published articles are made public. This includes manuscript files, peer review comments, author rebuttals and revised materials. Note: This was optional for articles submitted before 13 February 2023.
Peer reviewers are encouraged (but not required) to provide their names to the authors when submitting their peer review. If they agree to provide their name, then their personal profile page will reflect a public acknowledgment that they performed a review (even if the article is rejected). If the article is accepted, then reviewers who provided their name will be associated with the article itself.
Please consider the minor comments sent by reviewer 2. After you address the minor comments in this round of revision your paper should be acceptable for publication.
The authors have satisfactorily addressed all my previous comments. I consider that the manuscript now meets all PeerJ criteria in terms of basic reporting.
Again the authors have addressed all the comments I previously made and I consider that the manuscript reaches the standards required for publication.
All my comments have been met, with the conclusions being well stated, linked to the original research question and well described in the context of previous work.
no comment
Regarding my previous comments on the images outlined, could you add which was the rationale of choosing the number of images to be outlined? For example, did you make the segmentation every 5 mm?
To me, it is not entirely clear how you ended up with 6.3% (root mean square difference between volumes). I guess this number is an average among the different parts of the soleus, but how it is currently written in the result section seems related to the whole muscle volume. I suggest to rewrite that part.
In addition, since you mentioned that discrepancies larger than 2% mean errors in the segmentation, in the discussion I would add a sentence saying that the value of 6.3% obtained suggests possible errors in the volume extraction. Also acknowledge in the discussion that this reliability analysis is missing for the other variables.
I understand that the DTI was helpful for the segmentation but it is still unclear how the relevance for its contribution. I think it would be interesting to know how worse the reliability without the DTI data is. Anyway, I am not asking another investigation, but to just mention this point as possible future analysis
no comment
I thank the reviewer for the detailed revision. I just added few minor comments.
Dear authors. I now have comments from two reviewers that made positive assessments of your paper. I invite you to consider the comments from the reviewer and revised your manuscript. Please make sure you highlight the changes in the text, so it will be easier for reviewers and editors follow the changes.
The authors have submitted a very clearly written and presented manuscript. The article is well structured and results are relevant to the posed research questions and the figures are of high quality.
Links are provided to data files, which appear complete and are clearly documented with appropriate 'Read me' files.
The references cover the majority of relevant literature, although there do seem to be a couple of omissions:
1. Rana et al., (2013) J. Applied Physiology (115(1): 116-125) have reported ultrasound derived 3D fascicle orientations in the triceps surae, including soleus muscle. This should be mentioned in the literature review of the introduction and it would also be useful to include in the comparison of results described in the discussion section;
2. The authors suggestion of different roles for the anterior and posterior compartments of the muscle is supported by their data, and such partitioning of functional roles within muscle is not new. Again for completeness there should be some reference to previous work that has outlined similar ideas - for example: English et al., (1993) Physical Therapy 73: 857-867 - which will help readers interested in this topic access additional evidence for such ideas;
3. leading on from the comment above, it would also help strengthen the discussion if the manuscript indicated how different functions of the compartments could be controlled by the nervous system. As such reference to work that has shown 3d network of nerve branches through soleus and how they seem to parallel the architecural partitions would be valuable, eg. Loh et al., (2003) Clinical Anatomy 16: 378-382
The manuscript fits the aims and scope of the journal.
The manuscript clearly articulates how the work fills an identified gap in current knowledge and the methods used are innovative and performed to high technical and ethical standards.
The methods are in the most part described with sufficient detail, there are however a couple of areas where more information would be valuable:
1. methods L124 readers are referred to another publication for the scan setting details. For completeness it seems as though details should also be provided within this manuscript, to ensure that it stands alone as a self-contained piece of work with sufficient detail for replication;
2. There is no reference to the ethical approval number or associated documentation for the cadaver data;
3. Lines 165-167 describes the settings for the fibre tracking. It would be useful to know whether these were established using some form of standardised optimisation approach (and if so what was the protocol?); whether they are based on past experience of working with images of other muscles and/or whether they are specific to the soleus images analysed here.
4. As part of the fixing process for the cadaveric muscles, were they pinned or stretched to a certain length at all? I was left wondering whether the cadaver material could be equated to one or other of the ankle joint angles studied in the live participants? It could help in relating these two aspects of the study it were possible to make some indication on this point, maybe in the methods or discussion.
The data appear to be robust with sound statistical analysis. The conclusions are well stated and link to the original aims of the manuscript. There were a couple of areas for consideration:
1. L238 in results, states curvatures were 4 degrees larger in the posterior compartment. If this is curvature should it not be reported as /m or does this point refer to pennation angle?
2. Lines 242-244, reports that for every cm of MTU lengthening there were given changes in fascicle lengths, pennation angles and curvatures. However, this does assume a linear or constant change, which may well not be the case as the muscle transitions from shorter to longer lengths (e.g. Herbert et al., 2011 J. Physiol), this could be noted in a relevant place within the manuscript.
My final comment here is related to those made in the first section of the review, where reference to previous work suggesting partitioning of roles within muscles should be made; and links to possible pathways open to the nervous system to indepedently control different regions of the could muscles also be made.
Overall, this was a very enjoyable and interesting manuscript to read. It is good to see new information regarding in vivo muscle anatomy being presented.
The only additonal thought I had with regard the presented work was the potential for differential sensory feedback from structures, such as muscle spindles, from across the different muscle compartments. There could be potential of interplay between different intramuscular regions for the nervous system to 'understand' changes in soleus lengths and also possibility to have regional patterns of activation with sensory feedback from 'quieter' portions of the muscle. This may be something the authors wish to consider within the discussion as to the potential value of having such compartmentalised muscles, although I appreciate it would be speculation rather than facts these data support. I present this comment really as a point I thought the authors may find interesting to consider.
no comment
no comment
no comment
We thank the authors for this interesting work, which have reported in-vivo the architectural properties of the soleus. Here are my comments/suggestions.
line 19: I suggest to add the words dorsiflexion and plantarflexion for a better understanding of the ankle joint position
line 69: ‘With ultrasound, measurements can usually only be obtained from the most superficial (posterior and distal) compartment of the muscle’ This is a quite strong statement. Could you provide more information to support such statement or alternatively make this sentence more soft by saying that it depends on the US system used.
Line 112: how is the ankle passively dorsiflexed during the acquisition? Did you use any device to keep the joint in such position?
Line114-116. This part is not clear for me. I don’t understand how you achieved slack length of the medial gastrocnemius in dorsiflexion. I assume you mean ‘plantarflexion’ instead of dorsiflexion. Then you mentioned 108 deg in dorsiflexion: this I think is in plantarflexion. Please clarify this part.
Line 132. I think it is an useful information to mention (on average) the number of images outlined.
Line 138. This is a critical part. I understand that the DTI data were also used to support the segmentation but it is still unclear how you merged the two information (segmentation using MRI data and using DTI). As you mentioned, the muscle border is not always clear. Therefore, is it possible to provide some reliability data for the relevant outcomes (volume , fascicle lengths, pennation angle and curvature)?
I think it is important to discuss this limitation and eventually new reliability data in the discussion. This is useful for the reader in order to interpret correctly your relevant dataset .
Line 272. Could you explain the differences in terms of volume among your study, Ward and Hodgson?
All text and materials provided via this peer-review history page are made available under a Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.