Activity of Corrugator Muscle with Pressure Pain Stimulation in Healthy People

Round 1

Reviewer 1 Report

This study explored the relationship between pressure pain stimulation and corrugator activity in healthy adults, revealing that the specific shoulder point stimulation increased the corrugator muscle activity, suggesting its potential as an objective indicator of pressure pain.

Comments:

1          The introduction effectively outlines the study's background and purpose. The author should use shorter sentences and less repetitive words, this will improve the clarity and understanding (e.g., lines 39-41). Additionally, incorporating more linking words would enhance the overall flow of the introduction.

2          The methods are well-documented and described in detail. Ethical approval is appropriately mentioned. Although the description of the shoulder point is adequate, an additional image for better visualization would be beneficial for the reader. There is an error in formatting in lines 122&123, which should be part of the image description from line 120. In the "2.2.2 pressure pain threshold" and "2.2.3. pressure pain stimulation" sections, results are already presented, which would be more appropriately placed at the beginning of the results section.

3          The manuscript will benefit from moving the lines 104-106 and 111-114 to the Result section. This provides the first evaluation of pain thresholds that are used along the manuscript.

4          The manuscript will additionally benefit from including short introduction to each of the result parts.

5          While the figures are clear, it's important to further describe Figure 3. It should explain what is represented in the graph. Alternatively, Figure 3 could be merged with Figure 4, for a better flow (they are coming from the same dataset).

6          Regarding figure 6, it might be useful to the reader to see ns for non-significant difference between 1^st vs 2^nd, and 2^nd vs 3^rd.

7          The discussion is generally well documented, although certain points from the results require further discussion:

-       line 193-195/230-232: Are these the same two participants that are mentioned? Are these excluded?

-     The way the potential impacts are investigated and how they might be useful in the future for medical practice is worth mentioning, and the limitations are properly stated. The reviewer recommends a reorganization of the initial discussion to prioritize first the background information and then shortly wrap up the results.

-     The reviewer suggests to add a paragraph on the relevance of this method for the evaluation of pain sensitivity in chronic pain patients.

The study demonstrates a strong structure and approach; however, addressing the highlighted points is crucial before publication.

Sentences some times are too long and difficult to follow.
Add linking words between sentences

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

In this study, Yamada et al.,  investigated the activity of corrugator muscle associated with pain elicited by pressure stimulation. They also studied the relationship between its activity and pain intensity assessed by the Visual Analogue Scale in healthy participants. On behalf of their findings, authors clam to establish an objective manual pain assessment method using surface electromyography. 

There are some minor comments:

1. Did you compare the male vs female subjects in this study? What about the previous sEMG studies in males vs females? Did they find any sex difference in pain sensitivity?

2. Besides sex, age of the subjects can also affect the pain-sensitivity. Authors should discuss this in discussion section.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf