Potential Associations Between Anthropometric Characteristics, Biomarkers, and Sports Performance in Regional Ultra-Marathon Swimmers: A Quasi-Experimental Study

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Generally speaking, the present work is veru interesting and necessary, but the potential value of related research results from this work would be also limitied and insufficient. Even though the authors try to explore the underlying associations among anthropometric characteristics, biomarkers' changes, and sports performance in ultra-marathron swimming, which is actually beneficial for revealling potential relationship among these factors in regional swimmers, the highly small sample size has largerly limited the application and generalization of this research results. Except for this key weakness of this work, and meanwhile, several detailed issues have been also existed, and these have been listed as follows. Thank you!

1.The title can be revised as "Potential associations between anthropometic characteristics, biomarkers' changes, and sports performance in ultra-marathron swimming players: A quasi-experiment study".

2.The abstract should be properly enriched and enlargered, especially the results. And the conclusion is inaccurate, without any information about biomarkers' changes.

3.The keywords can be listed as"sports performance analysis; anthropometric characteristics; biomarkers' changes; ultra-marathron swimming; endurance performance; regional swimmers".

4.The introduction should be reasonably divided into several paragraphs and several necessary secondary titles can be also added to better express internal logic about this section.

5.Several special statistical symbols including r, R, p, no matter in tables and figures, or in text, these should be displayed with their italics form, yet the specific p-value will be not shown like that in the title of figure 1 and figure 2.

6.The clarity of figure 5 should be enhanced, and the R square should be placed next to the regression line.

7.The discussion seems too tedious and superficial, so more related literature should be increased to further discuss relevant research findings from this work, especially the negative results, which should be carefully and strictly interpreted and explained.

8. Since the present study has been related to human experiment, so the ethical statement should be validly proved by corresponding authoritative institution or organization.

9. The references should be further carefully and seriously checked and rectified by authors.

That's all, and thank you! 

Comments on the Quality of English Language

I suggest the English language could be properly improved to more clearly express the present research by authors, and thank you!

Author Response

Dear Reviewer 1

We really appreciate your comments on our manuscript. Your comments helped us to improve the manuscript.

C: Comment

A: Answer

 

C: Generally speaking, the present work is veru interesting and necessary, but the potential value of related research results from this work would be also limitied and insufficient. Even though the authors try to explore the underlying associations among anthropometric characteristics, biomarkers' changes, and sports performance in ultra-marathron swimming, which is actually beneficial for revealling potential relationship among these factors in regional swimmers, the highly small sample size has largerly limited the application and generalization of this research results. Except for this key weakness of this work, and meanwhile, several detailed issues have been also existed, and these have been listed as follows. Thank you!

 

A: Dear Reviewer 1, we appreciate your informative feedback. Also, we recognize the manuscript’s limitation regarding the sample size. However, we have addressed and explained point by point your valuable comments, which improved the clarity of the manuscript.

 

C: The title can be revised as "Potential associations between anthropometric characteristics, biomarkers' changes, and sports performance in ultra-marathon swimming players: A quasi-experiment study". 

A: Thank you for your suggestion. The title now is: Potential associations between anthropometric characteristics, biomarkers, and performance in regional ultra-marathon swimmers: A quasi-experimental study.

 

C: The abstract should be properly enriched and enlargered, especially the results. And the conclusion is inaccurate, without any information about biomarkers' changes.

A: We appreciate your suggestion. In the revised abstract, we have expanded the “Results” section to include more specific findings, such as the statistically significant decrease in biceps skinfold thickness (p = 0.022) and the observed increase in heart rate and blood pressure post-swim (p < 0.05). Additionally, the “Conclusions” section now accurately reflects the changes in these physiological biomarkers, highlighting their potential role in post-effort monitoring during ultra-endurance swimming.  Lines 33-55

 

C: The keywords can be listed as "sports performance analysis; anthropometric characteristics; biomarkers' changes; ultra-marathron swimming; endurance performance; regional swimmers". 

A: Thank you for your suggestion. Lines 58-59

 

C: The introduction should be reasonably divided into several paragraphs and several necessary secondary titles can also be added to better express internal logic about this section.

A: We thank the reviewer for this insightful observation. The introduction has been restructured into several distinct paragraphs, including two main subtitles: Gender and age, and Identifying ultra-marathon swimming, enhancing with that way the logical flow. Lines 61-134.

C: Several special statistical symbols including r, R, p, no matter in tables and figures, or in text, these should be displayed with their italics form, yet the specific p-value will be not shown like that in the title of figure 1 and figure 2.

A: We addressed the symbols with italics.

C: The clarity of figure 5 should be enhanced, and the R square should be placed next to the regression line.

A: Thank you for the detail. We addressed this difference. Line 304

 

 

C: The discussion seems too tedious and superficial, so more related literature should be increased to further discuss relevant research findings from this work, especially the negative results, which should be carefully and strictly interpreted and explained.

A: We appreciate the reviewer’s constructive critique. In response, we have revised and enriched the Discussion section by integrating additional relevant studies (e.g., Brobakken et al., 2023; Speedy et al., 2002; Knechtle et al., 2013) and providing a more critical analysis of the non-significant changes observed in body composition and anthropometric features. Special emphasis was placed on the interpretation of the stable anthropometric measures, which were contextualized through literature on homeostatic maintenance under aquatic ultra-endurance conditions. The implications of the negative findings have also been framed in relation to pacing and energy balance strategies. Lines: 316-391

C: Since the present study has been related to human experiment, the ethical statement should be validly proved by corresponding authoritative institution or organization.

A: We acknowledge this important point. We have now explicitly stated in the Participants (lines 155-161) and Institutional Review Board Statement (lines 440-444) sections that the Research Ethics and Deontology Committee of the Aristotle University of Thessaloniki was established in accordance with Article 21 of Law 4521/2018, which was published on March 2, 2018. Prior to this date, there was no obligation to submit a research proposal for approval, as such a requirement was not provided for by law.

C: The references should be further carefully and seriously checked and rectified by authors.

A: We have carefully checked the references.

C: I suggest the English language could be properly improved to more clearly express the present research by authors and thank you!

A: Thank you. We implemented a comprehensive English editing.

Reviewer 2 Report

Comments and Suggestions for Authors

I hope this letter finds you well. I had the opportunity to review your article titled, “Associations between anthropometric characteristics and performance in ultra-marathon swimming”, which was submitted Applied Sciences.

1. Abstract

- The research objectives, methods, results, and conclusions are logically arranged and follow a standard structure.

- The research purpose and basic structure are clearly stated, and the attempt to explore the relationship between body shape characteristics and performance in the specific sport of swimming is an academic contribution.

- However, it is unclear whether the conclusion that 'nutritional strategy and pacing may play a more crucial role' is derived from the experimental design or is an interpretation based on inference.

1. Introduction

- The introduction begins logically with a broad overview of existing studies on the effects of gender, age, and body composition on sports performance.

- It emphasizes the special nature of the research topic and the academic gap by presenting the special characteristics of the field of ultra-long distance swimming (horizontal posture, cold water environment, difficulty in nutrient absorption, etc.).

- Emphasizes the need for research by presenting inconsistent results (e.g., no relationship vs. presence of relationship between body composition and performance) in previous studies.

- It clearly demonstrates the academic breadth by comparing the gender difference in performance in ultra-long distance swimming and the best record time by age group.

- It is judged that the research framework of analyzing the relationship between physical changes and performance before and after swimming has been appropriately set.

- The study was written consistently and logically, focusing on swimming characteristics and performance factors.

- However, the research motivation and research problems are too broad and unclear.

- Lack of critical analysis of prior research. Most of it is limited to simple citations and listings, and there is a lack of interpretation or organization of conflicting research results and discussion of the limitations of existing methodologies.

- There is a lot of frequent use of conjunctions such as “Interestingly,” “However,” and “Therefore,” and there is a lack of clarity between subjects and verbs and redundant expressions.

2. Materials and Methods

- The study is a field-based design that utilizes ‘actual ultra-long-distance swimming performance (10 hours of continuous swimming)’, and is considered suitable for observing physiological and morphological responses in a real-life context.

- Based on the post-pre comparative design, we attempted to clarify the purpose of the study by measuring body measurements, physiological indices (BP, HR), and perceived exertion intensity (RPE).

- The 10-hour time period, free feeding/hydration management, and actual performance in a 50-meter swimming pool are considered to have high ecological validity.

- The body measurement tool meets ISAK standards and is considered reliable as it states that it was measured consistently by a certified anthropometrist.

- Paired t-test is used for pre- and post-comparison, and correlation analysis (Pearson’s r) is used appropriately.

- The normality test (Shapiro–Wilk test) and analysis software (SPSS) are clearly specified.

- However, the sample size (n=9) is very small, and the statistical power is bound to be low. In particular, in the case of correlation analysis, it is judged that it is difficult to rule out the possibility of chance results when n<10.

- Since the sample size is small, it is difficult to meet the assumption of normality, and it is necessary to mention the need to consider alternative nonparametric tests (e.g., Wilcoxon signed-rank test).

- In the case of the correlation coefficient (r = -0.682), the effect size is presented, but since in-depth analysis such as regression analysis was not performed, it is judged that the interpretation of the explanatory power (R²) is insufficient.

3. Results

- The results were presented relatively clearly in tables, figures, correlation coefficients, etc., and the information was conveyed accurately by presenting the mean and standard deviation of the numbers (M ± SD).

- Statistical results are specifically reported, such as changes in biceps skinfold thickness (p = 0.022), increases in blood pressure (BP) (p = 0.03), and negative correlation between post-swim hip circumference and distance (r = –0.682, p = 0.043).

- It provides realistic information by presenting specific data of the experimental environment, such as swimming distance, RPE (rating of perceived exertion), and time distribution by recovery type.

- Paired sample t-test and Pearson correlation analysis were used for statistical processing, and a normality test (Shapiro–Wilk) was also performed, so it is judged that the basic requirements were met.

- The finding of a relatively strong negative correlation of r = –0.682 (p = 0.043) in the correlation analysis can be seen as one of the major contributions of this study.

- However, despite the sample size being only 9, analyses were conducted on a large number of variables and there was no multiple comparison correction. This increases the possibility of type I error.

- The relationship between fatigue, recovery, and hydration/nutrition strategies, which was one of the research objectives, is virtually not mentioned in the results section, and in particular, nutritional intake exists only in the methods section and is not analyzed.

- The results of the statistical tests (p-value, effect size, etc.) are not fully described in the results table, limiting the interpretation by readers.

4. Discussion

- At the beginning of the discussion, the key results of this study (no change in most body measurements, decrease in biceps skinfold, increase in BP/HR, negative correlation between hip circumference and swimming distance) are concisely summarized.

- The interpretation that the negative correlation between hip circumference and swimming performance may be related to ‘reduced frontal resistance during swimming’ is a physiologically plausible approach.

- The value of the paper is increased by acknowledging the heterogeneity of the existing literature by introducing the fact that some papers showed significant fat reduction while others showed no change.

- The attempt to explain the absence of weight change by citing physiological principles such as fat oxidation rate, energy deficit (7700 kcal/kg fat), and body temperature maintenance is considered positive.

- The observation that the horizontal posture, aquatic environment, and low impact load during swimming may have contributed to the maintenance of body composition is considered scientifically sound.

- The part that suggests that coaches and athletes should focus on strategic factors rather than physical indicators clearly conveys the researcher's argument.

- However, the comparison with existing studies is mainly focused on simple listing, and it is judged that this study lacks comparative analysis of why there was no change.

- It is judged that the development of the discussion is excessively focused on justifying the results, and there is a lack of critical discussion on the weaknesses or limitations of the research design.

- Little is being done to determine which strategies are more effective or to provide specific, data-driven guidance from the research findings.

5. Conclusion

- The conclusion concisely summarizes the key findings of this study.

- The overall alignment between the research objective (to determine the relationship between physical characteristics and performance in ultra-endurance swimming) and the conclusions is considered good.

- The conclusion provides practical direction by suggesting that personalized pacing strategies, physical strength, and nutritional strategies may have a greater impact on ultra-endurance swimming than physical characteristics.

- The conclusion provides practical direction by suggesting that personalized pacing strategies, physical strength, and nutritional strategies may have a greater impact on ultra-endurance swimming than physical characteristics.

- However, the last sentence of the conclusion remains a relative evaluation that ‘strategic factors are more important than static body characteristics’, and there is a lack of quantitative evidence on which factor was actually more effective.

- Major limitations of the study (e.g., sample size of only 9, only males, no control group, lack of real-time physiological measurements, etc.) are not stated in the conclusions.

 

Author Response

Dear Reviewer 2

We appreciate your comments on our manuscript. Additionally, we appreciated that you pointed out first the positive parts of our study and thereafter its issues. Concluding, your comments helped us to improve the manuscript.

C: Comment

A: Answer

 

C: Abstract

- The research objectives, methods, results, and conclusions are logically arranged and follow a standard structure.

- The research purpose and basic structure are clearly stated, and the attempt to explore the relationship between body shape characteristics and performance in the specific sport of swimming is an academic contribution.

- However, it is unclear whether the conclusion that 'nutritional strategy and pacing may play a more crucial role' is derived from the experimental design or is an interpretation based on inference.

A: We thank the reviewer for this important clarification request. The conclusion regarding the importance of nutritional strategy and pacing is based on observed indirect indicators, such as the stable pacing pattern, progressive RPE scores, consistent swimming rhythm, and the absence of major physiological deterioration across the 10-hour effort. While not tested through direct experimental manipulation, this interpretation is supported by descriptive findings and aligned with existing endurance literature. To address this, we have revised the conclusion to clearly distinguish empirical observations from inferred interpretations. Lines 47-55.

 

C: Introduction

- The introduction begins logically with a broad overview of existing studies on the effects of gender, age, and body composition on sports performance.

- It emphasizes the special nature of the research topic and the academic gap by presenting the special characteristics of the field of ultra-long-distance swimming (horizontal posture, cold water environment, difficulty in nutrient absorption, etc.).

- Emphasizes the need for research by presenting inconsistent results (e.g., no relationship vs. presence of relationship between body composition and performance) in previous studies.

- It clearly demonstrates the academic breadth by comparing the gender difference in performance in ultra-long distance swimming and the best record time by age group.

- It is judged that the research framework of analyzing the relationship between physical changes and performance before and after swimming has been appropriately set.

- The study was written consistently and logically, focusing on swimming characteristics and performance factors.

- However, the research motivation and research problems are too broad and unclear.

A: We understand your point. For this reason, we included more references in the introduction and a clearer aim at the end of it. Lines 61-134.

C: Lack of critical analysis of prior research. Most of it is limited to simple citations and listings, and there is a lack of interpretation or organization of conflicting research results and discussion of the limitations of existing methodologies.

A: We appreciate your perspective and would like to clarify that the purpose of the introduction is to present a comprehensive overview of the key factors influencing ultra-marathon swimming. A critical analysis of these factors, which is an essential component of our study, is provided in detail in the Discussion section. Lines 316-391.

C: There is a lot of frequent use of conjunctions such as “Interestingly,” “However,” and “Therefore,” and there is a lack of clarity between subjects and verbs and redundant expressions.

A: Thank you for pointing that out. We have reviewed the manuscript thoroughly and revised multiple sentences to reduce the overuse of conjunctions such as “Interestingly” and “However,” improve clarity in subject-verb agreement, and eliminate redundant expressions. These changes aim to enhance the overall readability and precision of the manuscript.

 

 

 

 

C: Materials and Methods

- The study is a field-based design that utilizes ‘actual ultra-long-distance swimming performance (10 hours of continuous swimming)’, and is considered suitable for observing physiological and morphological responses in a real-life context.

- Based on the post-pre comparative design, we attempted to clarify the purpose of the study by measuring body measurements, physiological indices (BP, HR), and perceived exertion intensity (RPE).

- The 10-hour time period, free feeding/hydration management, and actual performance in a 50-meter swimming pool are considered to have high ecological validity.

- The body measurement tool meets ISAK standards and is considered reliable as it states that it was measured consistently by a certified anthropometrist.

- Paired t-test is used for pre- and post-comparison, and correlation analysis (Pearson’s r) is used appropriately.

- The normality test (Shapiro–Wilk test) and analysis software (SPSS) are clearly specified.

- However, the sample size (n=9) is very small, and the statistical power is bound to be low. In particular, in the case of correlation analysis, it is judged that it is difficult to rule out the possibility of chance results when n<10.  Since the sample size is small, it is difficult to meet the assumption of normality, and it is necessary to mention the need to consider alternative nonparametric tests (e.g., Wilcoxon signed-rank test).

A: We recognize the limitation of the small sample size, and for that reason, we acknowledged it as a limitation of our study (line 384). However, as stated in the Introduction, previous studies on ultra-marathon swimming have shown no substantial differences between samples in similar contexts.

1. Knechtle, B., Rosemann, T., Lepers, R., & Rüst, C. (2014). Women outperform men in ultradistance swimming: The Manhattan Island Marathon Swim from 1983 to 2013. International Journal of Sports Physiology and Performance, 9, 913–924.
2. Vogt, P., Rüst, C., Rosemann, T., Lepers, R., & Knechtle, B. (2013). Analysis of 10 km swimming performance of elite male and female open-water swimmers. SpringerPlus, 2, 603.

Additionally, we conducted a priori sample size (n) calculation to ascertain that a sample size of 9 participants, giving a 66% chance to reject the null hypothesis, will be needed to detect significant differences. Also, the Shapiro–Wilk test (appropriate for samples under 51 participants) indicated no statistically significant deviation from normality. Therefore, we proceeded with parametric analyses. Lines 213-222.

 

C: In the case of the correlation coefficient (r = -0.682), the effect size is presented, but since in-depth analysis such as regression analysis was not performed, it is judged that the interpretation of the explanatory power (R²) is insufficient.

A: Thank you for pointing that out. Due to the small sample size, it is challenging to perform a reliable regression analysis. This type of analysis, especially when considering multiple influencing factors, requires a larger number of participants to ensure statistical power and validity. Our perspective aligns with the findings of Khamis and Kepler (2010) in their work titled "Sample Size in Multiple Regression," which emphasizes the importance of adequate sample size for robust regression modeling. Of course, with your comment, we addressed it as an additional limitation of our study. Lines 387-388.

 

C: Results

- The results were presented relatively clearly in tables, figures, correlation coefficients, etc., and the information was conveyed accurately by presenting the mean and standard deviation of the numbers (M ± SD).

- Statistical results are specifically reported, such as changes in biceps skinfold thickness (p = 0.022), increases in blood pressure (BP) (p = 0.03), and negative correlation between post-swim hip circumference and distance (r = –0.682, p = 0.043).

- It provides realistic information by presenting specific data of the experimental environment, such as swimming distance, RPE (rating of perceived exertion), and time distribution by recovery type.

- Paired sample t-test and Pearson correlation analysis were used for statistical processing, and a normality test (Shapiro–Wilk) was also performed, so it is judged that the basic requirements were met.

- The finding of a relatively strong negative correlation of r = –0.682 (p = 0.043) in the correlation analysis can be seen as one of the major contributions of this study.

-However, despite the sample size being only 9, analyses were conducted on a large number of variables and there was no multiple comparison correction. This increases the possibility of type I error.

A: We acknowledge the potential risk of a Type I error. To address this, we limited the number of statistical tests performed and avoided repeated comparisons. While lowering the significance level (α) from 0.05 to 0.01 could further reduce the risk of Type I error, we chose not to do so, as this would increase the likelihood of a Type II error, particularly given the small sample size. Concluding, we refer to the small sample size as a limitation of our study. Lines 383-384.

C: The relationship between fatigue, recovery, and hydration/nutrition strategies, which was one of the research objectives, is virtually not mentioned in the results section, and in particular, nutritional intake exists only in the methods section and is not analyzed.

A: We thank the reviewer for this insightful observation. In the revised manuscript, we have added relevant information in the Results and Discussion sections to better reflect the interplay between fatigue (as expressed by RPE progression), recovery distribution (active vs. passive), and nutritional intake strategies (Line 284). Although individual dietary analysis was beyond the scope of this observational study, we provided descriptive insight into food intake types and recovery time allocation, and highlighted their potential association with endurance maintenance. This clarification strengthens the contextual understanding of fatigue and pacing regulation during the 10-hour effort. Moreover, we mentioned it as a perspective for future study. Lines  388-389.

 

C: The results of the statistical tests (p-value, effect size, etc.) are not fully described in the results table, limiting the interpretation by readers.

A: With your comment, we inserted the p – values in both tables 2 and 3. Lines 287 & 297.

Discussion

- At the beginning of the discussion, the key results of this study (no change in most body measurements, decrease in biceps skinfold, increase in BP/HR, negative correlation between hip circumference and swimming distance) are concisely summarized.

- The interpretation that the negative correlation between hip circumference and swimming performance may be related to ‘reduced frontal resistance during swimming’ is a physiologically plausible approach.

- The value of the paper is increased by acknowledging the heterogeneity of the existing literature by introducing the fact that some papers showed significant fat reduction while others showed no change.

- The attempt to explain the absence of weight change by citing physiological principles such as fat oxidation rate, energy deficit (7700 kcal/kg fat), and body temperature maintenance is considered positive.

- The observation that the horizontal posture, aquatic environment, and low impact load during swimming may have contributed to the maintenance of body composition is considered scientifically sound.

- The part that suggests that coaches and athletes should focus on strategic factors rather than physical indicators clearly conveys the researcher's argument.

- However, the comparison with existing studies is mainly focused on simple listing, and it is judged that this study lacks comparative analysis of why there was no change.

A: Following your suggestion, we have strengthened the Discussion section by providing a more in-depth comparison of our results with those of other authors. I hope this expansion satisfies you. Lines 316-391.

C: It is judged that the development of the discussion is excessively focused on justifying the results, and there is a lack of critical discussion on the weaknesses or limitations of the research design.

A: We appreciate this valuable observation. We have now expanded the final paragraph of the Discussion section to include a more critical reflection on the limitations of the study design, such as the lack of control over nutrition/pacing variables and absence of continuous physiological monitoring. This aims to balance the interpretative insights with methodological transparency. Lines 316-391.

C:  Little is being done to determine which strategies are more effective or to provide specific, data-driven guidance from the research findings.

A: We agree and have addressed this by expanding the Discussion section (in the “Nutrition and Recovery” subsection) with more emphasis on practical implications and future directions for research, including the need for controlled trials to quantify the impact of nutrition and pacing strategies. Lines 371-382.

C: Conclusion

- The conclusion concisely summarizes the key findings of this study.

- The overall alignment between the research objective (to determine the relationship between physical characteristics and performance in ultra-endurance swimming) and the conclusions is considered good.

- The conclusion provides practical direction by suggesting that personalized pacing strategies, physical strength, and nutritional strategies may have a greater impact on ultra-endurance swimming than physical characteristics.

- The conclusion provides practical direction by suggesting that personalized pacing strategies, physical strength, and nutritional strategies may have a greater impact on ultra-endurance swimming than physical characteristics.

- However, the last sentence of the conclusion remains a relative evaluation that ‘strategic factors are more important than static body characteristics’, and there is a lack of quantitative evidence on which factor was actually more effective.

A: Thank you for pointing this out. We have rephrased the final sentence of the Conclusions section to reflect a more cautious interpretation, clarifying that while static anthropometric characteristics showed minimal impact, no direct statistical testing was performed for strategic factors. Lines 393-414.

 

C: Major limitations of the study (e.g., sample size of only 9, only males, no control group, lack of real-time physiological measurements, etc.) are not stated in the conclusions.

A: We appreciate the reviewer’s critical point. We have now explicitly acknowledged the study’s main limitations in the Discussion (lines 383-391) and Conclusions (lines 393-412) sections, including the small sample size, gender-specific selection, absence of a control group, and lack of continuous physiological monitoring during the swim. This transparency aims to clarify the generalizability and contextual interpretation of our findings, and it sets the stage for future research to address these methodological boundaries.

Reviewer 3 Report

Comments and Suggestions for Authors

Thank you for the opportunity to evaluate this scientific paper, which addresses a niche topic, but of interest in the field of extreme sports performance. The paper has the merit of proposing an analytical approach regarding the relationship between anthropometric characteristics and performance in ultra-endurance swimming, but certain methodological and interpretative aspects require attention to support the conclusions formulated. In the following, I will summarize my main observations, organized by chapters:

- Introduction
A discrepancy can be observed between the theoretical foundation and the operationalized objectives. Although the impact of age and gender on performance in endurance swimming is mentioned, the study is limited to an exclusively male sample, without this decision being argued in the introduction. The lack of justification limits the conceptual clarity of the study and reduces the generalization force. A more solid theoretical framework would have been necessary that would link the hypotheses to the sample structure and the variables investigated.

-Materials and Methods

The methodology raises a major issue regarding the statistical validity of the results. The sample is very small (n = 9), which significantly affects the power of the test and the applicability of the conclusions. No justification is provided regarding the selection or impossibility of expanding the sample, and the absence of a statistical power calculation is notable. Also, no methods are mentioned to control for confounding factors such as nutritional intake or individual conditions of the participants, which can significantly influence the physiological data and performance.

-Results
The presentation of the results is insufficient from an interpretative perspective. Certain insignificant correlations are only briefly mentioned, without a critical analysis of possible causes or implications. In addition, there is a lack of tables or figures that would clearly contextualize these results and provide a coherent overall view. The focus on a single statistically significant outcome (hip circumference) is not supported by a multivariate approach that would eliminate collateral influences.

-Discussion
The interpretation of the data raises questions about scientific rigor. The claim that a smaller hip circumference reduces forward resistance is made without direct biomechanical support, which risks overinterpreting the statistical correlation. Also, discrepancies with other relevant studies (e.g., Knechtle et al. 2022 vs. Speedy et al. 2002) are not sufficiently discussed, which limits the integration of the results into a broader scientific framework and affects the external validation of the conclusions.

Author Response

Dear Reviewer 3

We really appreciate your comments on our manuscript. Your comments helped us to improve the manuscript.

C: Comment

A: Answer

 

C:  Introduction
A discrepancy can be observed between the theoretical foundation and the operationalized objectives. Although the impact of age and gender on performance in endurance swimming is mentioned, the study is limited to an exclusively male sample, without this decision being argued in the introduction. The lack of justification limits the conceptual clarity of the study and reduces the generalization force. A more solid theoretical framework would have been necessary that would link the hypotheses to the sample structure and the variables investigated.

A: Thank you for pointing that out. We recognize the limitations of our study. We have mentioned in both Materials and methods, discussion and the conclusion the reason why only male swimmers participated (lines: 137-138 & 383-384). Also, we mention the avoidance of the results’ generalization (lines 389-391).

Materials and Methods

C: The methodology raises a major issue regarding the statistical validity of the results. The sample is very small (n = 9), which significantly affects the power of the test and the applicability of the conclusions. No justification is provided regarding the selection or impossibility of expanding the sample, and the absence of statistical power calculation is notable. Also, no methods are mentioned to control for confounding factors such as nutritional intake or individual conditions of the participants, which can significantly influence the physiological data and performance.

A: We recognize the limitation of the small sample size, and for that reason, we acknowledged it as a limitation of our study (line: 382). However, as stated in the Introduction, previous studies on ultra-marathon swimming have shown no substantial differences between samples in similar contexts.

1. Knechtle, B., Rosemann, T., Lepers, R., & Rüst, C. (2014). Women outperform men in ultradistance swimming: The Manhattan Island Marathon Swim from 1983 to 2013. International Journal of Sports Physiology and Performance, 9, 913–924.
2. Vogt, P., Rüst, C., Rosemann, T., Lepers, R., & Knechtle, B. (2013). Analysis of 10 km swimming performance of elite male and female open-water swimmers. SpringerPlus, 2, 603.

Additionally, we conducted a priori sample size (n) calculation ascertain that a sample size of 9 participants, giving a 66% chance to reject the null hypothesis, will be needed to detect significant differences. Also, the Shapiro–Wilk test (appropriate for samples under 51 participants) indicated no statistically significant deviation from normality. Therefore, we proceeded with parametric analyses. Lines 213-217. Also, although individual dietary analysis was beyond the scope of this observational study, we provided descriptive insight into food intake types and recovery time allocation, and highlighted their potential association with endurance maintenance. This clarification strengthens the contextual understanding of fatigue and pacing regulation during the 10-hour effort.

 

C:Results
The presentation of the results is insufficient from an interpretative perspective. Certain insignificant correlations are only briefly mentioned, without a critical analysis of possible causes or implications. In addition, there is a lack of tables or figures that would clearly contextualize these results and provide a coherent overall view. The focus on a single statistically significant outcome (hip circumference) is not supported by a multivariate approach that would eliminate collateral influences.

A: We tried to depict our results. We recognize that there are many significant differences between the studied variables. However, we explain compare, and discuss them in the Discussion. Also, in the Results section, we present three tables and five figures that illustrate all the analyzed data. Furthermore, in the revised manuscript, we have expanded the Discussion to include a detailed critical analysis, exploring the potential causes and implications of our findings in comparison with the existing literature on the topic. Lines 316-391.

 

C: Discussion
The interpretation of the data raises questions about scientific rigor. The claim that a smaller hip circumference reduces forward resistance is made without direct biomechanical support, which risks overinterpreting the statistical correlation. Also, discrepancies with other relevant studies (e.g., Knechtle et al. 2022 vs. Speedy et al. 2002) are not sufficiently discussed, which limits the integration of the results into a broader scientific framework and affects the external validation of the conclusions.

A: Thank you for your valuable suggestion. We agree that the claim regarding smaller hip circumference reducing forward resistance lacks direct biomechanical evidence and may risk overinterpreting a statistical correlation. In the revised manuscript, we have acknowledged the absence of supporting biomechanical analysis and have adjusted the interpretation accordingly (lines 338-341). Additionally, we have expanded the discussion to provide a more thorough comparison between our findings and the referenced literature. lines: 338-360.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Generally speaking, the revised manuscript has been largely improved by authors, but several detailed issues have been also existed and should be rectified by authors. Thank you！

1. Several special symbol including n, P, and F should be presented by their italics form. no matter in tables or in text.
2. The Conlcusion can be properly refined and further concise.

Comments on the Quality of English Language

I advise the English language of this manuscript could be improved to more clearly express the research, and thank you!

Author Response

Dear Reviewer

1. The clearer version of the manuscript helped us to detect the missing italics.
2. We minimized the Conclusion, deleting the last sentences which are ordinary with the Discussion. 
3. We addreessed again the English language.

Thank you very much for your contribution in the improvement of our manuscript.

Reviewer 3 Report

Comments and Suggestions for Authors

I believe that the authors have correctly understood and completed the aspects noted in the initial review.

Author Response

Dear Reviewer 

We are glad for your appreciation of our work. Thank you very much for your constructive comments. 

Kind regards