Differences in Pressure Pain Threshold and Strain Elastography Between Women with and Without Fibromyalgia: A Cross-Sectional Study

Point-by-point response to Comments and Suggestions for Authors

·       Comment 1: The objective should be clearly defined (in the introduction: its better to describe that this is aimed to compare the PPL and SEL between control and FM

Response 1: We appreciate this suggestion. We have revised the Introduction to state the objective more explicitly and consistently, emphasizing that the study aims to compare pressure pain threshold (PPT) and soft tissue elastic properties assessed by ultrasound strain elastography (SEL) between women with fibromyalgia and healthy controls at standardized tender-point sites. This revision improves clarity and aligns the Introduction with the Abstract and Methods.

·       Comment 2: There is an important missing issue: were the FM group treated? What medications? How to control this variable? How is this variable be related to the outcome for example: as mentioned in the abstract, specific upper limb regions may reflect local biomechanical factors”?

Response 2: Thank you for this important observation. We agree that treatment and medication use may influence pain sensitivity and potentially tissue mechanical behavior. In the revised manuscript, we have clarified that participants in the fibromyalgia group did not receive any study-related treatment/intervention at the time of assessment, as stated in the Methods. However, detailed medication profiling (type/dose/duration) was not collected in a standardized manner, and therefore it could not be incorporated as a covariate. We have now explicitly acknowledged this as a limitation and we have tempered the interpretation of between-group difference, particularly at upper-limb sites, because local biomechanical factors and systemic factors (including medication) could contribute to site-specific heterogeneity.

·       Comment 3: The diagnosis time of FM, how long is the expected diagnosis? Also, other variables such as smoking, other meds for menopause? Etc.

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Response 3: Thank you for pointing this out. We agree that time since diagnosis and lifestyle/clinical factors (e.g., smoking, menopausal hormone therapy, and other medications) could influence pain processing and potentially soft tissue characteristics. These variables were not collected in a standardized manner in the present study; therefore, they could not be included in the analyses. We have now acknowledged this explicitly as a limitation and highlighted it as a key consideration for future longitudinal studies.

“The absence of systematically collected data on pharmacological management, time since diagnosis, smoking status, menopausal hormone therapy, and other concomitant medications precluded control for these potential confounders, which may have affected pain sensitivity and possibly SEL-derived tissue deformation.”

·       Comment 4: Some language issues were found, such as missing capital letters as in the abstract at the start of sentences

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Response 4: Thank you for pointing this out. The manuscript was carefully revised to correct language issues, including missing capital letters at the beginning of sentences, particularly in the abstract.

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Point-by-point response to Comments and Suggestions for Authors

·       Comment 1: Title. The title does not clearly distinguish strain elastography from shear wave elastography, which may mislead readers regarding the type of elastic property measured.

·       The term “elastic properties” is overly broad and risks overinterpretation of the biomechanical meaning of the findings.

Response 1: Thank you for this important point. The title has been revised to (i) explicitly specify ultrasound strain elastography (rather than elastography in general) and (ii) avoid the overly broad and potentially mechanistically overreaching term “elastic properties.” The revised wording refers to strain elastography to better reflect what is measured in this study.

Comments 2: Abstract

·       The Introduction includes aim-like statements rather than focusing on the rationale.

·       The study aim is stated more than once and in different formulations.

·       The Methods section contains narrative details rather than concise methodological information.

·       The Results section uses vague, non-scientific phrasing (e.g. “improving trend”).

·       The Conclusion contains conceptually inaccurate wording and overgeneralised claims that are not sufficiently qualified by heterogeneity or study design.

Response 2: The Abstract has been comprehensively revised to improve scientific tone and internal consistency. Specifically: (i) the Background now focuses on rationale and knowledge gap, (ii) the aim is stated once using a single formulation, (iii) the Methods are presented concisely (design, sample, outcomes, sites, statistics), (iv) vague language has been removed, and (v) the Conclusions have been rephrased to avoid overgeneralization and to reflect the semi-quantitative nature of strain elastography and the site-specific heterogeneity observed, with appropriate caution due to the cross-sectional design.

Comments 3: Introduction

·       The scientific rationale is not clearly articulated early; the knowledge gap emerges late.

·       The distinction between peripheral tissue alterations and central sensitisation is not conceptually clarified.

·       The novelty of using strain elastography to compare fibromyalgia and healthy controls is insufficiently justified.

·       Prior elastography literature is summarised without clearly identifying what remains unresolved.

Response 3: The Introduction has been restructured to articulate the knowledge gap earlier and to clarify the conceptual distinction between central sensitization and potential peripheral tissue-related alterations. The rationale for applying strain elastography (as distinct from shear wave elastography and other techniques) has been strengthened, and prior elastography literature is now summarized to explicitly identify what remains unresolved—namely, the lack of between-group comparisons at standardized tender-point sites using SEL alongside PPT.

Comments 4:  Methods

4.1 Study Design and Participants

·       The recruitment strategy is unclear (consecutive vs. convenience sampling).

·       Potential selection bias is not adequately acknowledged.

·       The rationale for including only women is not explicitly justified.

Response 4.1: The recruitment strategy has been clarified, and potential selection bias has been explicitly acknowledged. In addition, the rationale for including only women has been added to improve external validity interpretation and to justify sex-specific sampling given FM epidemiology and known sex-related differences in pain sensitivity.

4.2 Pressure Pain Threshold

·       Familiarisation effects and learning bias are not addressed.

·       Reliability of repeated PPT measurements is not clearly documented.

Response 4.2: The PPT procedure has been expanded to explicitly report steps intended to reduce learning bias (standardized instructions, consistent assessor, triplicate measurements averaged, and consistent test order), and the limitation of not providing formal reliability estimates has been acknowledged.

4.3 Ultrasound Strain Elastography

·       The compression protocol (2–5 mm) is insufficiently described and not reproducible.

·       It is unclear how the compression magnitude was monitored or standardised.

·       The term “dedicated software” is undefined.

·       Operator dependence is not adequately addressed.

·       No intra- or inter-rater reliability data are provided.

Response 4.3: The SEL protocol has been expanded to ensure reproducibility: participant/probe positioning, definition of the ‘dedicated software’ as the device’s built-in quality control (green-bar feedback), compression monitoring (2–5 mm), ROI definition (5 mm), retention of high-quality sequences only, and averaging of three acquisitions per site. Operator experience (13 years) has also been added.

Furthermore, it has been explicitly acknowledged that SEL is operator-dependent and that intra- and inter-rater reliability were not assessed, which may affect reproducibility and interpretability.

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4.4 Statistical Analysis

·       Extensive multiple comparisons are performed without correction.

·       No effect sizes are reported.

·       The increased risk of Type I error is not acknowledged.

·       Statistical significance is prioritised without sufficient emphasis on clinical relevance.

Response 4.4.: Thank you for this important recommendation. The Statistical Analysis section has been revised to explicitly acknowledge the increased risk of Type I error due to multiple testing across anatomical sites. In addition, effect sizes have been incorporated to quantify the magnitude of between-group differences independently of p-values. Specifically, Cohen’s d has been added to the results tables for PPT and SEL outcomes to facilitate interpretation of magnitude and to complement the mean differences and 95% confidence intervals. The Results and Discussion have also been edited to emphasize interpretation based on effect magnitude and confidence intervals rather than statistical significance alone, and all findings are framed as exploratory in the context of a cross-sectional observational design.

Comments 5. Results

·       The Results section contains interpretive statements that belong in the Discussion.

·       Excessive repetition of numerical values already presented in tables.

·       Non-significant findings are over-explained.

·       Terminology is inconsistent (e.g. intervention vs experimental group).

·       Internal consistency between text, tables, and figures is not explicitly ensured.

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·       Response 5: The Results section has been edited to present findings descriptively, move interpretive statements to the Discussion, reduce redundancy with tables, and standardize terminology (control vs FM group). Internal consistency between text and tables has been checked and corrected where needed (e.g., abbreviations and group labels).

6. Discussion

·       The Discussion is overly long and lacks a clear internal structure.

·       Subgroup and site-specific findings are overinterpreted despite an exploratory design.

·       Speculative mechanistic explanations are not consistently labelled as hypotheses.

·       Sex-based interpretations rely on behavioural assumptions without direct evidence.

·       The implications of heterogeneous findings across anatomical sites are insufficiently addressed.

·       Response 6: The Discussion has been restructured with clearer sub-sections (principal findings, comparison with literature, interpretation, heterogeneity across sites, clinical implications, limitations). Mechanistic explanations are now explicitly framed as hypotheses, subgroup/site-specific observations are interpreted as exploratory, and sex-based interpretations have been removed or substantially qualified given the absence of direct behavioral or biological measures. Greater emphasis is placed on the heterogeneity across anatomical sites and on the limitations inherent to SEL and cross-sectional design.

7. Clinical Implications

·       The clinical applicability of strain elastography is implied, without longitudinal or diagnostic validation.

·       Cross-sectional findings are discussed in a way that may suggest assessment utility beyond the evidence.

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·       Response 7: The Clinical Implications section has been revised to avoid implying diagnostic or longitudinal utility. The text now states that SEL findings are preliminary and exploratory, and that clinical applicability requires confirmatory studies with diagnostic validation and longitudinal/interventional designs.

8. Limitations

·       Limitations are scattered rather than consolidated.

·       Key methodological constraints (operator dependence, multiple testing) are under-emphatised.

·       The impact of these limitations on interpretability is not sufficiently discussed.

Response 8: Thank you for your contribution. The limitations section has been improved by emphasizing convenience sampling/selection bias, operator dependence and lack of reliability assessment for SEL, multiple testing risk, and unmeasured confounding (medication/diagnosis duration/smoking/hormone therapy.

9. Conclusion

·       Conclusions are overly generalised relative to the data.

·       Insufficient acknowledgement of methodological limitations.

·       The balance between supported findings and unresolved questions is unclear.

·       The tone is more definitive than justified by a cross-sectional design.

Response 9: The Conclusions have been revised to better match the data and study design. Wording has been tempered to reflect the exploratory, cross-sectional nature of the study and the semi-quantitative character of SEL-derived measures, explicitly acknowledging site-specific heterogeneity and methodological limitations.

Point 1: The manuscript is generally understandable; however, the English quality needs improvement to ensure clarity and precision. Several sections contain grammatical inconsistencies, overly long or complex sentences, imprecise wording, and occasional misuse of technical terminology. These issues sometimes obscure meaning, particularly in the Methods and Discussion sections. A thorough revision by a native English speaker or a professional language editing service is strongly recommended to improve readability and ensure that the scientific content is communicated clearly and unambiguously.

Response to point 1: Thank you for this valuable recommendation. The manuscript has been thoroughly revised to improve English clarity, precision, and consistency. Grammatical inconsistencies, overly long or complex sentences, and imprecise wording have been corrected throughout, with particular attention to the Methods and Discussion sections. Technical terminology has also been standardized (e.g., consistent use of “ultrasound strain elastography (SEL)” and avoidance of overly broad biomechanical terms), and ambiguous phrasing has been edited to ensure that the scientific content is communicated clearly and unambiguously.

Comment 1: 1. Exploratory Nature and Multiple Comparisons

The study performs a very large number of between-group comparisons (26 anatomical sites × 2 outcomes), which substantially increases the risk of Type I error. Although the authors acknowledge this issue in the Discussion, the analytical framework and presentation of results remain largely confirmatory (e.g., extensive reporting of p-values and “statistically significant differences”).

Required revisions:

·       1.1. Explicitly define the analyses as exploratory in the Methods section, not only in the Discussion.

·       1.2. Reduce emphasis on statistical significance and prioritise effect sizes and confidence intervals throughout the Results.

·       1.3. Provide a clearer justification for not applying any correction for multiple comparisons (e.g., false discovery rate), or alternatively implement such a strategy.

·       If no correction is applied, the conclusions should be further tempered to reflect hypothesis-generating rather than confirmatory findings.

Response 1.1: This clarification was included at the end of Section 2.4 (Methodology), stating that the analyses performed using ultrasound strain elastography and pressure pain threshold had a purely exploratory nature.

Response 1.2: The effect sizes with the largest magnitudes have been specifically highlighted in the tables presented in the Results section to facilitate their identification and interpretation.

Response 1.3: Thank you for this important point. The revised manuscript now explicitly addresses the increased Type I error (false-positive) risk associated with multiple anatomical-site comparisons. To mitigate this risk, p-values were adjusted using false discovery rate (FDR) control (Benjamini–Hochberg; q = 0.05) across the set of site-level tests, and the resulting adjusted p-values are reported in the revised tables. For p-values originally reported as “<0.001”, a conservative value of 0.001 was used for the adjustment. After FDR correction, PPT differences remained statistically significant across all sites, whereas SEL differences remained significant at most sites (19/26), with several locations no longer reaching significance after correction (including forearm, paraspinal, and lateral pectoral regions). The Results, Discussion, and Conclusions have been updated accordingly to reflect the exploratory nature of multi-site SEL findings.

Comments 2: 2. Interpretation of Strain Elastography (SEL)

SEL is repeatedly discussed as reflecting “elastic properties” of tissue, which risks overinterpretation. Strain elastography provides a semi-quantitative deformation-based measure under operator-applied compression, not a direct biomechanical assessment of tissue stiffness.

While this limitation is acknowledged later in the Discussion, the earlier framing (Introduction, Objectives, Abstract) implies a stronger mechanistic interpretation than is warranted.

Response 2: Thank you for this suggestion. We have carefully revised the manuscript to describe SEL consistently as a deformation-based imaging technique rather than a direct measure of tissue stiffness or elasticity. All relevant sections have been updated accordingly.

Comments 3: Measurement Reliability and Operator Dependence

Strain elastography is known to be operator-dependent. Although measurements were performed by an experienced examiner and averaged across trials, no intra- or inter-rater reliability data are provided.

Given that many SEL differences are small to moderate and site-dependent, the lack of reliability assessment is a major limitation.

Required revisions:

·       Explicitly acknowledge in the Methods (not only Limitations) that intra- and inter-rater reliability were not assessed or add them.

·       Further temper interpretation of site-specific SEL differences in light of this limitation.

·       If available, reference prior work using the same protocol that reports reliability; otherwise, clearly state this as a critical gap for future research.

Response 3: We thank the reviewer for this suggestion. In response, we have clarified in the Methods section that all SEL and PPT measurements were performed by a single experienced evaluator. We have also explicitly acknowledged that intra-observer reliability was not formally assessed in the present study. This information has now been added to the Methods to ensure full transparency and to complement the limitation already described in the Limitations section. We agree that this clarification improves the methodological accuracy of the manuscript.

Comments 4:  Results Presentation and Redundancy

The Results section is lengthy and highly repetitive, with extensive textual duplication of information already presented in tables. Multiple tables also contain overlapping content, which impairs readability.

Required revisions:

·       Streamline the Results section by reducing repetition of anatomical site lists.

·       Avoid restating full table contents verbatim in the text.

·       Consider reducing the number of tables or clearly separating descriptive from inferential results.

·       Highlight patterns (e.g., consistent PPT reduction vs heterogeneous SEL findings) rather than listing each site repeatedly.

Response 4: We thank the reviewer for this constructive comment. In response, we have thoroughly revised the Results section to address issues of redundancy and readability. Specifically, we have removed the textual descriptions that duplicated information already presented in the tables, thereby avoiding verbatim restatement of results. The revised version now emphasizes global patterns—namely, the uniform reduction in PPT values across all sites and the heterogeneous, site-dependent nature of SEL findings—rather than providing detailed site-by-site descriptions, which are now presented exclusively in the tables.

In addition, the tables have been reorganized to clearly separate descriptive data from those reporting between-group differences. Different types of tables are now located in separate subsections: tables containing descriptive information are presented in Section 3.1, whereas tables showing between-group comparisons are presented in Section 3.2.

We believe that these changes have streamlined the presentation of the Results section, reduced unnecessary repetition, and substantially improved the clarity and readability of the manuscript.

Comments 5. Conceptual Coherence: Central vs Peripheral Mechanisms

The manuscript appropriately emphasises central sensitisation as the dominant explanatory framework for FM. However, some passages alternately suggest that SEL findings reflect meaningful peripheral tissue alterations, creating conceptual ambiguity.

Required revisions:

·       Maintain a consistent conceptual position that central sensitisation is primary.

·       Frame SEL findings as secondary, heterogeneous, or non-specific peripheral adaptations, not as evidence of primary peripheral pathology.

·       Explicitly state that the results do not support SEL as a mechanistic or diagnostic biomarker.

Response 5: we have carefully revised the Discussion to ensure full conceptual coherence. Central sensitization is now consistently emphasized as the primary explanatory framework for fibromyalgia, while SEL findings are framed as secondary, heterogeneous, and non-specific deformation patterns rather than as evidence of primary peripheral pathology.

We have removed wording suggesting intrinsic tissue alterations and have standardized terminology throughout the manuscript to describe SEL as a deformation-based imaging technique. Additionally, we have explicitly stated that the present results do not support the use of SEL as a mechanistic or diagnostic biomarker in FM.

We believe that these revisions fully address the reviewer’s concern and ensure a clear and consistent interpretation across all sections.

Comments 6. Sample Size Justification

The rationale for inflating the sample size to account for a “62.5% dropout rate” is unclear in a cross-sectional study, where dropout is typically not applicable.

Required revisions:

·       Clarify or revise the sample size justification to align with the study design and exploratory aims.

Response 6: We appreciate this comment. The reference to an anticipated “dropout rate” has been removed, as this concept is not applicable to a cross-sectional design. The sample size justification has been revised to clarify that the final sample was increased to enhance statistical precision and robustness for the planned between-group comparisons rather than to compensate for participant attrition. The corresponding paragraph in the Methods section has been rewritten accordingly.

7. Minor Comments

7.1.  Terminology

Use “non-dominant” consistently instead of “no dominant.”

Standardise terminology for SEL outcomes (avoid alternating between elasticity, stiffness, and elastic properties)

Response 7.1: We thank the reviewer for these helpful comments. The manuscript has been carefully revised to address both terminology issues.

First, the term “non-dominant” has now been used consistently throughout the manuscript, replacing all previous instances of “no dominant.”

Second, terminology related to strain elastography outcomes has been fully standardized. References to “elasticity,” “stiffness,” or “elastic properties” have been removed, and SEL findings are now consistently described as “SEL-derived tissue deformation measures”, in line with the methodological nature of the technique.

7.2.  Methods Clarity

Clarify whether assessors were blinded to group allocation.

Specify how limb dominance was determined (self-report vs objective criteria).

Response 7.2.: In response, both points have now been addressed in the revised manuscript.

The Methods section has been updated to explicitly state that the assessor was not blinded to group allocation. Additionally, we have clarified that limb dominance was determined based on participant self-report.

We believe that these additions improve the methodological transparency and clarity of the manuscript.

 7.3: Tables

Tables are dense and difficult to interpret; consider highlighting only sites with moderate-to-large effect sizes.

Ensure consistency between tables and narrative descriptions.

Response 7.3: We thank the reviewer for this helpful suggestion. To facilitate the readability and interpretation of the tables, we have implemented a clear highlighting system. Variables with the most relevant results have been emphasized in bold. In addition, statistically significant values (p (raw) <0.05 and p(FDR-BH) < 0.05) are marked with a single asterisk (*), while effect sizes considered moderate-to-large (Cohen’s d > 0.50) are indicated with three asterisks (***).

A corresponding explanatory note describing this notation has been included at the bottom of each table to ensure transparency and consistency. We have also carefully reviewed all tables and the narrative descriptions to guarantee full alignment between tabulated data and the text.

7.4   Language

Minor grammatical and stylistic issues remain, but overall readability is acceptable.

The Discussion could be shortened by reducing repetition.

Response 7.4: the manuscript has been carefully reviewed for language and style, and minor grammatical and typographical issues have been corrected to further improve clarity and readability.

Regarding the Discussion section, while no content was removed to preserve the completeness of the scientific argument, the text has been revised for style and flow to minimize redundancy and improve coherence.

Point 1: The manuscript is generally well written, with clear structure and appropriate use of scientific terminology. The English language is of good overall quality and allows the reader to follow the rationale, methods, and findings without major difficulty.

However, there are minor to moderate issues that should be addressed to improve clarity and readability:

·       Occasional grammatical inaccuracies (e.g., subject–verb agreement, article use).

·       Inconsistent terminology (e.g., alternating use of “elastic properties,” “elasticity,” and “strain elastography values”).

·       Some sentences are overly long or repetitive, particularly in the Introduction and Discussion, and could be streamlined.

·       Minor typographical issues and inconsistent phrasing (e.g., “no dominant” instead of “non-dominant”).

These issues do not detract from the scientific content. Still, a careful language edit, preferably by a fluent English speaker or professional editing service, would improve precision, conciseness, and overall readability.

Response point 1: We thank the reviewer for this positive and constructive feedback. We appreciate the recognition of the overall clarity, structure, and scientific quality of the manuscript.

In response to the points raised, the manuscript has undergone a comprehensive language and style revision. All minor grammatical inaccuracies, including issues related to subject–verb agreement and article use, have been carefully corrected.

Terminology has been fully standardized throughout the manuscript. Specifically, inconsistent expressions such as “elastic properties,” “elasticity,” and similar terms have been replaced with consistent and methodologically accurate terminology referring to “SEL-derived tissue deformation measures.”

Sentences that were overly long or repetitive, particularly in the Introduction and Discussion sections, have been revised and streamlined to improve clarity and conciseness. Minor typographical issues and inconsistent phrasing have also been corrected, including the replacement of “no dominant” with the correct term “non-dominant.”

In addition, the revised manuscript has been reviewed by a fluent native English speaker to ensure accuracy, coherence, and overall readability.

We believe that these revisions have fully addressed the reviewer’s language-related suggestions and have further improved the quality of the manuscript.

Comment 1: Interpretation of Strain Elastography (Critical)

The manuscript must restrict the interpretation of strain elastography (SEL) findings.

·       SEL should be explicitly described as an operator-dependent, semi-quantitative measure of tissue deformation under compression, not a direct measure of tissue stiffness, elasticity, inflammation, or pathology.

·       All mechanistic interpretations linking SEL findings to inflammatory processes, neurotransmitter alterations, autonomic dysfunction, or peripheral tissue pathology must be removed or clearly labelled as speculative.

·       The Abstract and Discussion must explicitly state that SEL findings areexploratory and non-diagnostic.

Response 1: We thank the reviewer for this important and constructive feedback. The manuscript has been thoroughly revised to restrict the interpretation of strain elastography (SEL) findings and to clarify the methodological and conceptual scope of this technique.

Specifically, SEL is now consistently described throughout the manuscript as an operator-dependent, semi-quantitative imaging technique that reflects tissue deformation under standardized compression, rather than a direct measure of tissue stiffness, elasticity, inflammation, or pathology. This clarification has been incorporated in all sections. All mechanistic interpretations linking SEL findings to inflammatory processes, neurotransmitter alterations, autonomic dysfunction, or primary peripheral tissue pathology have been removed or explicitly reframed as speculative, and are discussed independently of SEL-derived measures. The Discussion has been revised to clearly separate established central pain mechanisms in fibromyalgia from the descriptive, non-specific nature of SEL outputs.

In addition, both the abstract and discussion now explicitly state that SEL findings are exploratory and non-diagnostic, and that no causal or mechanistic inferences can be drawn from the present cross-sectional design. The operator dependence of SEL and the absence of formal intra- and inter-rater reliability assessment are also emphasized as key methodological limitations.

Comments 2: Methodological Limitations (Critical)

The Limitations section must be expanded and strengthened to acknowledge explicitly:

Lack of assessor blinding

·       Absence of intra-rater reliability assessment for SEL

·       Operator-dependent nature of strain elastography

·       Cross-sectional design (no causal inference)

·       Large number of site-level comparisons despite FDR correction

·       Convenience sampling from a single private clinic

·       Inclusion of women only

·       Absence of control for physical activity level, occupational exposure, or medication use

These limitations should be stated clearly and without mitigation language.

Response 2: The limitations section has been substantially expanded and strengthened to explicitly acknowledge all the methodological constraints highlighted.

Specifically, the revised manuscript now clearly states the lack of assessor blinding, the operator-dependent nature of strain elastography, and the absence of formal intra-rater reliability assessment for SEL acquisition and interpretation. The cross-sectional design is explicitly identified as a limitation that precludes causal, mechanistic, or temporal inferences.

In addition, we now clearly acknowledge the large number of site-level comparisons, noting that, despite false discovery rate correction, residual Type I error risk and site-dependent heterogeneity cannot be fully excluded. The use of convenience sampling from a single private rehabilitation clinic and the inclusion of women only are also explicitly stated as factors limiting external validity and generalizability.

Finally, the absence of systematic control for physical activity levels, occupational exposure, pharmacological management, and other concomitant treatments is now clearly acknowledged as a limitation that may have influenced pain sensitivity and SEL-derived tissue deformation measures.

Comments 3: Statistical and Inferential Framing

·       Despite using the Benjamini–Hochberg correction, the authors must clarify that site-specific SEL findings are descriptive rather than confirmatory.

·       Heterogeneity in SEL effect sizes across anatomical locations should be emphasised, and claims of a coherent peripheral pattern should be avoided.

Response 3:

We confirm that the manuscript has been revised throughout to ensure that site-specific SEL findings are explicitly framed as descriptive and exploratory rather than confirmatory, despite the use of false discovery rate correction.

Heterogeneity in SEL effect sizes across anatomical locations is now consistently emphasized, including explicit reporting of effect size ranges, identification of anatomical sites without significant between-group differences, and repeated clarification that SEL findings are site-dependent and non-uniform. Claims suggesting a coherent or uniform peripheral tissue pattern have been avoided.

Comments 4: Clinical Claims

·       The manuscript must explicitly state that SEL cannot be considered a diagnostic or screening tool for fibromyalgia based on the present data.

·       The Discussion should clearly distinguish between:

·       robust PPT findings supporting central sensitisation, and

·       heterogeneous SEL findings that likely reflect secondary or non-specific adaptations.

Response 4: the manuscript now explicitly states that strain elastography (SEL) cannot be considered a diagnostic or screening tool for fibromyalgia based on the present data and that SEL findings are exploratory and non-diagnostic. The Discussion clearly distinguishes between robust PPT findings supporting central sensitisation and heterogeneous, site-dependent SEL findings interpreted as secondary or non-specific adaptations rather than a coherent peripheral pattern.

Comments 5: Discussion Length and Focus

·       Repetitive explanations of central sensitisation and neurochemical mechanisms not directly measured should be removed.

·       The Discussion should focus on:

·       the contrast between PPT and SEL findings,

·       site-dependent variability,

·       implications for future hypothesis-driven research.

Response 5: The Discussion has been revised to remove repetitive explanations of central sensitisation and neurochemical mechanisms not directly measured in the present study. The revised Discussion now focuses on the contrast between robust PPT findings and heterogeneous, site-dependent SEL findings, emphasizes variability across anatomical locations, and highlights implications for future hypothesis-driven, longitudinal, and interventional research.

Comments 6: 6. Abstract Revision

·       The Abstract conclusion must be revised to:

·       emphasise the consistency and magnitude of PPT differences,

·       describe SEL findings as heterogeneous and exploratory,

·       avoid implications of peripheral tissue pathology.

Response 6: The abstract conclusion has been revised to emphasize the consistency of pressure pain threshold (PPT) differences across all assessed sites, to describe strain elastography (SEL) findings as heterogeneous and exploratory, and to avoid any implication of peripheral tissue pathology. SEL findings are explicitly framed as non-diagnostic and site-dependent.

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Comments 7: 7. Terminology Consistency

·       Replace any remaining references to “elasticity” or “stiffness” with “tissue deformation” when referring to SEL outcomes.

·       Ensure no causal language remains.

Response 7: The manuscript has been carefully revised to ensure terminological consistency. All remaining references to “elasticity” or “stiffness” have been replaced with “tissue deformation” when referring to strain elastography (SEL) outcomes. In addition, causal language has been removed, and SEL findings are consistently described as descriptive, exploratory, and non-diagnostic throughout the manuscript.

Point 1: The manuscript is generally well written, with clear structure and appropriate use of scientific terminology. The English language is of good overall quality and allows the reader to follow the rationale, methods, and findings without major difficulty.

However, there are minor to moderate issues that should be addressed to improve clarity and readability:

·       Occasional grammatical inaccuracies (e.g., subject–verb agreement, article use).

·       Inconsistent terminology (e.g., alternating use of “elastic properties,” “elasticity,” and “strain elastography values”).

·       Some sentences are overly long or repetitive, particularly in the Introduction and Discussion, and could be streamlined.

·       Minor typographical issues and inconsistent phrasing (e.g., “no dominant” instead of “non-dominant”).

These issues do not detract from the scientific content. Still, a careful language edit, preferably by a fluent English speaker or professional editing service, would improve precision, conciseness, and overall readability.

Response point 1: We thank the reviewer for the positive evaluation of the manuscript’s structure, clarity, and scientific content. We have carefully revised the manuscript to address the minor to moderate language issues noted. Specifically, grammatical inaccuracies have been corrected, terminology has been standardized (e.g., consistent use of “strain elastography” and “tissue deformation”), overly long or repetitive sentences have been streamlined, and minor typographical errors and inconsistent phrasing (e.g., “non-dominant”) have been corrected throughout the text. The revised version has been reviewed by a native English speaker to further improve clarity, precision, and overall readability.

Point-by-point response to Comments and Suggestions for Authors

Comment 1: Primary vs exploratory outcomes

·       Explicitly state whether PPT or SEL was treated as the primary outcome, and frame all site-specific SEL analyses as exploratory.

Response 1: We thank the reviewer for this clarification. The manuscript has been revised to explicitly state that PPT was treated as the primary outcome of the study, given its established relevance in fibromyalgia research. All SEL analyses are now clearly framed as exploratory and site-specific, and are described as hypothesis-generating rather than confirmatory. This clarification has been incorporated into the Methods and reinforced in the Limitations section.

Comments 2: Discussion length and redundancy

·       The Discussion could be modestly shortened by reducing repetition around central sensitisation and operator dependence, which are already clearly acknowledged.

Response 2: We thank the reviewer for this suggestion. The Discussion has been carefully reviewed to reduce unnecessary repetition and improve conciseness, particularly regarding central sensitisation and the operator-dependent nature of strain elastography, while preserving the content required to appropriately contextualize and interpret the findings. These minor adjustments were made to enhance readability without altering the scientific message.

Comments 3: Consistency of terminology

·       Ensure consistent use of terms such as “tissue deformation,” “SEL-derived measures,” and “semi-quantitative output” throughout the manuscript to avoid subtle redundancy.

·       .

Response 3: We thank the reviewer for this comment. Terminological consistency was addressed in a previous revision, and the manuscript has already been carefully standardized to ensure consistent use of terms such as “tissue deformation,” “SEL-derived measures,” and “semi-quantitative output” when referring to strain elastography outcomes. This terminology is now used consistently across all sections to avoid redundancy or conceptual ambiguity.

Comments 4: Abstract phrasing

·       The Abstract is appropriately cautious but could be marginally tightened by removing one repeated reference to heterogeneity or exploratory interpretation.

Response 4: The Abstract has been marginally revised to reduce minor repetition regarding heterogeneity and exploratory interpretation, while preserving the cautious framing of the findings. This adjustment was made to improve conciseness and readability without altering the scientific message.

Comments 5: Figure/table cross-referencing

·       Ensure all tables and figures are explicitly referenced in the Results text in sequential order.

Response 5: The Results section has been carefully checked to ensure that all tables and figures are explicitly referenced in sequential order. All figures and tables are now clearly cited in the Results text in the order in which they appear.

Comments 6: Methodological detail

·       Clarify whether the mean of dominant and non-dominant sites was ever considered, or state explicitly that all analyses were site-specific only.

Response 6: The Methods section has been revised to explicitly clarify that all analyses were conducted on a site-specific basis and that no averaging of dominant and non-dominant sides was performed at any stage of the analysis. This clarification has been added to the Statistical Analysis subsection.

Comments 7: Language polishing

·       Minor grammatical and stylistic edits remain (e.g., hyphenation, line-break artefacts from revisions), but these do not affect content.

Response 7: The manuscript has been carefully proofread to address minor grammatical and stylistic issues, including hyphenation inconsistencies and line-break artefacts introduced during revision. These edits were made to improve readability and presentation without affecting the scientific content.

Point 1: The overall quality of the English language is good and generally clear, and the manuscript is understandable throughout. Minor grammatical issues, occasional awkward phrasing, and some redundancy remain, particularly in the Discussion section. A light round of professional language editing or careful proofreading would further improve clarity and flow, but is not essential for comprehension.

Response point 1: We thank the reviewer for the positive assessment of the manuscript’s clarity and overall language quality. The manuscript has undergone a careful proofreading to address minor grammatical issues, awkward phrasing, and redundancy, particularly in the Discussion section. In addition, the revised version has been reviewed by a native English speaker to further improve clarity and flow, without altering the scientific content.