Changes in the Infrared Thermographic Response of the Triceps Suralis Muscle During Ankle Flexion–Extension Until Exhaustion in Healthy Adults

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

First of all I would like to thank the authors for their work.

Please forgive my english mistakes but I will leave original text to make you sure that this review is not AI generated.

In general, this work is very good. But as always, there are things that can be improved and I want to list them.

1. First of all solve the "Tsk" issue in the text. Abbervations are at the end of paper and you did not explain this at first use, so unfamiliar reader will not know its skin temperature. So you are using letters and abbervations of terms in the abstract that noone will have the chance to fully understand until going through text and thats mistake.
2. Decide if you want to use tsk or Tsk and make it unformous through the paper.
3. You had enough space to put figure from data capture to see the setting. It will improve its replicability.
4. In line 140 i do not know what does "5" mean.
5. To replicate this study, researchers need to know what was this constant speed of execution (line 142)
6. Do I understand properly that each participant may reach 100% fatigue at different time? In table one there is information, that there was high variability of repetitions and I think thats important point that could be discuss broader, but anayway you did right choice to use fatigue in %.
7. There should be written description of results in table 1, not only table as you did in 3.2
8. Isnt figure 3b enough? it is extended version of what we see at figure 3a.
9. Disscussion is mature and adequate.
10. As physiotherapist and bussines-oriented guy I find lacking of more specific of usefulness of this solutions. What is a cost of this device? How are obtained data more meaningful than alternative methods? Will using your solution make meaningful impact in diagnosis? How do you see use of this solution on a broader scale and how it will affect athletes?
11. Conclusion should containg summary of findings, so brief description what you did is welcomed as separate paragraphs before your final word that you put there.
12. I do not like that you did not go for open science flow with open repository as new standards in European Union, but it is your choice not a mistake to be punished for.

In conclusion,  please be sure to extend at least some point from the issues I present you.

Good luck with your future research!

 

 

Author Response

REVIEWER 1

First of all, I would like to thank the authors for their work.

 

Please forgive my english mistakes but I will leave original text to make you sure that this review is not AI generated.

 

In general, this work is very good. But as always, there are things that can be improved, and I want to list them.

 

We thank the reviewer for their constructive and helpful feedback on our manuscript. We have replied to each specific comment in the section below and have introduced the corresponding edits into the manuscript using Word’s track changes.

 

1. First of all solve the "Tsk" issue in the text. Abbervations are at the end of paper and you did not explain this at first use, so unfamiliar reader will not know its skin temperature. So you are using letters and abbervations of terms in the abstract that noone will have the chance to fully understand until going through text and thats mistake.

 

Response: Amended

 

2. Decide if you want to use tsk or Tsk and make it unformous through the paper.

 

Response: Amended

 

3. You had enough space to put figure from data capture to see the setting. It will improve its replicability.

 

Response: Thank you for your comment.

 

4. In line 140 i do not know what does "5" mean.

 

Response: Thank you very much for your contribution. We have proceeded to remove that aspect.

 

 

5. To replicate this study, researchers need to know what was this constant speed of execution (line 142).

 

Thank you very much for your contribution. We have proceeded to explain the stress test times in greater detail. Lines 179-182

 

6. Do I understand properly that each participant may reach 100% fatigue at different time? In table one there is information, that there was high variability of repetitions and I think thats important point that could be discuss broader, but anayway you did right choice to use fatigue in %.

 

 

Response: Thank you for your comment. Following your suggestion, we will make the relevant changes in the discussion.

 

7. There should be written description of results in table 1, not only table as you did in 3.2.

 

Response: Thank you for your comment. Following your suggestion, we have introduced new text to provide greater clarity to the data in Table 1.

 

8. Isnt figure 3b enough? it is extended version of what we see at figure 3a.

 

Response: Thank you for your comment. Figure 3a represents the data taking only gender into account, whereas Figure 3b represents the data taking gender and age into account. Therefore, the two figures do not represent the same data.

 

9. Disscussion is mature and adequate.

 

Response: Thank you for your comment.

 

10. As physiotherapist and bussines-oriented guy I find lacking of more specific of usefulness of this solutions. What is a cost of this device? How are obtained data more meaningful than alternative methods? Will using your solution make meaningful impact in diagnosis? How do you see use of this solution on a broader scale and how it will affect athletes?

 

Response: We appreciate your valuable feedback. We would like to take this opportunity to clarify the practical implications and potential applicability of thermography in the field of sports science and performance monitoring.

 

Thermography is a non-invasive, non-contact, real-time assessment tool that allows for the analysis of physiological responses related to muscle fatigue, inflammation, and recovery processes. Compared to traditional methods, such as measuring blood biomarkers, manual palpation, or subjective pain scales, thermographic data provides objective and spatial information on skin temperature distribution, facilitating the early detection of asymmetries or abnormal thermal patterns associated with fatigue or delayed onset muscle soreness (DOMS).

 

In terms of cost and practical applicability, professional thermographic devices have become increasingly accessible, with high-precision equipment ranging from approximately $2,000 to $6,000, depending on their resolution and sensitivity. Once purchased, the device involves minimal operating costs, as data capture and analysis can be performed quickly and repeatedly, without the need for consumables or causing discomfort to the participant.

 

From a diagnostic standpoint, thermography is not intended to replace clinical or biochemical assessments, but rather to complement them by providing a functional indicator of peripheral thermoregulation status, tissue stress, and physiological recovery. Integrating thermography with other performance indicators and physiological variables can improve the accuracy of training load management and injury prevention.

 

On a broader scale, the application of thermography can contribute to the development of personalized athlete monitoring systems, allowing coaches and medical staff to identify changes in recovery dynamics and detect early signs of overtraining or localized fatigue. Consequently, this approach can optimize decision-making in training and rehabilitation processes, improving both the performance and safety of the athlete.

 

11. Conclusion should containg summary of findings, so brief description what you did is welcomed as separate paragraphs before your final word that you put there.

 

Response: Thank you very much for your comment. We have added the following paragraph: The results observed in this study evidencing that infrared thermography is a valid tool for the measurement, analysis, and quantification of the tissue metabolic response of the muscular system before, during and after exercise, showing changes in skin temperature throughout the maximum muscle fatigue protocol. However, due to the study design, it has not been possible to compare these thermal changes with serum values or biomarkers. Line 382-387

 

 

12. I do not like that you did not go for open science flow with open repository as new standards in European Union, but it is your choice not a mistake to be punished for.

 

Response: We understand your concern. In future projects, we will try to change this policy and upload the data to open repositories. I must say in our defense that, in order to submit this article, we had to upload a database to the “Sports” platform, and we are always willing to provide the data to any reviewer or editor who requests it. Thank you for your comment.

 

Author comment: We appreciate all the comments made on our manuscript, which helped improve it’s quality.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Please use the following observations and suggestions as advice on how to potentially enhance the manuscript. These come from a place of earnest interest in the manuscript. 

Lines 25-26: The abstract reports that the "ANOVA model detected no significant differences in the interaction time x sex (p=0.110), side x sex (p=0.095) and time x side x sex (p=0.641)." This is a result, and it would be more appropriate to state the main finding from the results section in the conclusion of the abstract, as this section is a summary of the entire paper. The conclusion of the abstract does a better job of this.

Line 41: The text states that metabolic by-products "generate alterations in vascular dynamics which can modulate peripheral blood flow and, consequently, surface skin temperature." This is a key point, but a citation is provided here that may not directly support this broad statement. The citation should be checked to ensure it fully supports the claim.

Lines 72-73: The authors state that discrepancies in the literature may stem from "heterogeneous study designs, small and non-comparable samples, and limited assessment windows focused only on pre- and post-exercise measures." This is an excellent justification for the study, and it could be made more impactful by providing a specific example of a study with these limitations and how the present study addresses it.

Lines 74-75: The statement "Importantly, it has been uncommon to conduct continuous monitoring during exercise protocols, which has limited our comprehension of the dynamic thermoregulatory adjustments that take place in real time" is a strong point, but it could be rephrased to be more active and less wordy.

Line 85: The study is described as an "open cross-sectional descriptive observational study." It's good that the authors used the STROBE guidelines, but a brief explanation of how this design fits the research question would be helpful for the reader.

Lines 103-104: The recruitment method "open advertisement" is mentioned, but more detail about where this advertisement was placed (e.g., posters, social media) would be beneficial.

Lines 117-118: The use of an air-conditioned room at a constant temperature and humidity is a strength, but the authors mention that there were no "electronic devices or sources of artificial light and heat near the measurement point." It would be good practice to specify what was considered "near" in this context.

Lines 120-125: The method for taking photos every 5 repetitions and then subdividing them into quartiles seems to have a typo or is not fully clear. The example states that for 100 repetitions, the images analyzed are at T0, T5, T10, T15, and T20. This does not correspond to the 25%, 50%, 75%, and 100% effort points. This section requires significant clarification and correction to ensure the methodology is reproducible.

Lines 141-142: It is stated that patients had to maintain a "constant speed of execution." Was this speed measured or controlled in any way, or was it a subjective assessment by the observer? This is a crucial detail for reproducibility.

Lines 149-150: The authors mention that the gastrocnemius area was chosen due to its extensive research and the "straightforwardness in conducting and evaluating both the physical and thermographic assessments." It is unclear what is "straightforward" about this area compared to others. The authors should provide a more specific justification.

Line 173: The text presents the results of the two-way repeated measures ANOVA, but the results for the side factor (p=<0.001) are not fully supported in the body of the text. The post-hoc analysis shows p-values for specific quartiles, but the overall effect of side should be explained more clearly.

Line 174: The text mentions a "trend" in the interaction of time x side. It would be helpful to explicitly state what this trend was, even if it was not statistically significant.

Lines 195-197: This section repeats the results from the abstract and results section. It is a good practice to summarize the findings here, but the repetition of the exact numerical results is not necessary.

Lines 201-202: The authors state that a temperature difference of over 0.6 degrees C could be an indicator of a pathological condition. It is a good point, but the source for this claim should be double-checked to ensure it supports this specific cutoff.

Lines 211-213: The discussion notes that "descriptively no differences greater than 0.1 degrees C were observed in both sexes, between sides, in the comparison between sexes, mean AT values equal to 0.7 degrees C were obtained." The phrasing is slightly confusing; it should be made clearer that the small differences were found between sides, while a larger difference was found between sexes.

Lines 235-236: The authors suggest that a decrease in skin temperature in men is evidence of "peripheral vasoconstriction that redirects blood to the most active muscles." This is an interesting hypothesis, but it is not directly tested. The authors should use more cautious language, such as "may suggest" or "is consistent with."

Lines 278-279: The manuscript mentions a limitation of the study was that assessments took place between 8 am and 5 pm and that this could have led to "inconsistencies in skin temperature among the individuals" due to circadian rhythms. This is a critical point that should be addressed in the methodology section, as it affects the validity of the study.

Lines 298-300: The conclusion states that IRT is a "valid tool for the measurement, analysis, and quantification of the tissue metabolic response." While the study's results support this, it is important to explicitly state the limitations of using IRT for this purpose, as noted in the discussion (e.g., it does not directly measure deep muscle activity).

 

Author Response

REVIEWER 2

 

Please use the following observations and suggestions as advice on how to potentially enhance the manuscript. These come from a place of earnest interest in the manuscript. 

 

We thank the reviewer for their constructive and helpful feedback on our manuscript. We have replied to each specific comment in the section below and have introduced the corresponding edits into the manuscript using Word’s track changes.

 

Lines 25-26: The abstract reports that the "ANOVA model detected no significant differences in the interaction time x sex (p=0.110), side x sex (p=0.095) and time x side x sex (p=0.641)." This is a result, and it would be more appropriate to state the main finding from the results section in the conclusion of the abstract, as this section is a summary of the entire paper. The conclusion of the abstract does a better job of this.

 

Response: Thank you for your comment. Following your suggestion, we have modified the abstract.

 

Line 41: The text states that metabolic by-products "generate alterations in vascular dynamics which can modulate peripheral blood flow and, consequently, surface skin temperature." This is a key point, but a citation is provided here that may not directly support this broad statement. The citation should be checked to ensure it fully supports the claim.

 

Response: Thank you very much for your contribution. We have reviewed and corrected the bibliographic citation.

 

Lines 72-73: The authors state that discrepancies in the literature may stem from "heterogeneous study designs, small and non-comparable samples, and limited assessment windows focused only on pre- and post-exercise measures." This is an excellent justification for the study, and it could be made more impactful by providing a specific example of a study with these limitations and how the present study addresses it.

 

Response: Thank you for your comment. Following your comments, we have rewritten this sentence (lines 76-81) and added a new paragraph (lines 85-90).

 

Lines 74-75: The statement "Importantly, it has been uncommon to conduct continuous monitoring during exercise protocols, which has limited our comprehension of the dynamic thermoregulatory adjustments that take place in real time" is a strong point, but it could be rephrased to be more active and less wordy.

 

Response: Thank you for your comment. Following your comments, we have rewritten this sentence (lines 83-84).

 

Line 85: The study is described as an "open cross-sectional descriptive observational study." It's good that the authors used the STROBE guidelines, but a brief explanation of how this design fits the research question would be helpful for the reader.

 

Response: Thank you for your comment. Following your comments, we have introduced new text (lines 122-127).

 

Lines 103-104: The recruitment method "open advertisement" is mentioned, but more detail about where this advertisement was placed (e.g., posters, social media) would be beneficial.

 

Response: Amended.

 

Lines 117-118: The use of an air-conditioned room at a constant temperature and humidity is a strength, but the authors mention that there were no "electronic devices or sources of artificial light and heat near the measurement point." It would be good practice to specify what was considered "near" in this context.

 

Response: Thank you very much for your contribution. Near the measurement point refers to the location of the patients. There were no sources of cold or heat pointing directly at the volunteers' station, thus avoiding elements that could influence their skin temperature.

 

Lines 120-125: The method for taking photos every 5 repetitions and then subdividing them into quartiles seems to have a typo or is not fully clear. The example states that for 100 repetitions, the images analyzed are at T0 , T5 , T10, T15, and T20. This does not correspond to the 25%, 50%, 75%, and 100% effort points. This section requires significant clarification and correction to ensure the methodology is reproducible.

 

Response: Thank you very much for your contribution. We have explained this concept in more detail below. It has also been described in more detail in the text. For example, if a volunteer performed 100 repetitions, since every 5 repetitions an image was recorded, the basal image (T0) 0 repetition, image 5 (T1) 25 repetition, image 10 (T2) 50 repetition, image 15 (T3) 75 repetition and image 20 (T4) 100 repetition

 

Lines 141-142: It is stated that patients had to maintain a "constant speed of execution." Was this speed measured or controlled in any way, or was it a subjective assessment by the observer? This is a crucial detail for reproducibility.

 

Response: Thank you very much for your contribution. Below, we have provided a more detailed explanation of the standardization protocol for the dorsal flexion and plantar flexion tests in relation to time. One second of eccentric phase, dorsiflexion, and one second of concentric phase, plantar flexion, was calculated using a digital stopwatch and verbally indicated by one of the researchers).

 

 

Lines 149-150: The authors mention that the gastrocnemius area was chosen due to its extensive research and the "straightforwardness in conducting and evaluating both the physical and thermographic assessments." It is unclear what is "straightforward" about this area compared to others. The authors should provide a more specific justification.

 

Response: Thank you very much for your contribution. We believe that this area is easier and more comfortable than other regions, as it allows measurements to be taken without the patient having to undress or wear underwear (anterior chest, abdominal, lumbar, thoracic, cervical, quadriceps, or hamstring regions).

 

Line 173: The text presents the results of the two-way repeated measures ANOVA, but the results for the side factor (p=<0.001) are not fully supported in the body of the text. The post-hoc analysis shows p-values for specific quartiles, but the overall effect of side should be explained more clearly.

 

Response: Thank you for your comment. We acknowledge that the “side” factor showed statistical significance (p < 0.001) in the repeated measures ANOVA, but this result was not highlighted due to its limited physiological relevance. Since the analysis included both men and women, the interaction between sex and side could have generated additional variability that makes it difficult to clearly interpret this effect.

 

Line 174: The text mentions a "trend" in the interaction of time x side. It would be helpful to explicitly state what this trend was, even if it was not statistically significant.

 

Response: Thank you for this observation. In this study, the term “trend” refers to a statistically insignificant trend, usually associated with p-values between 0.05 and 0.80. This indicates that, although the interaction between time and side did not reach conventional statistical significance (p < 0.05), it showed interesting behavior.

 

Specifically, the results showed a slight tendency for skin temperature to be lower on one side compared to the other as exercise intensity increased. This subtle response could become significant in future studies with a larger sample size or higher temporal resolution.

 

Therefore, we use the term “trend” to acknowledge this emerging pattern while avoiding overinterpretation of a non-significant result.

 

Lines 195-197: This section repeats the results from the abstract and results section. It is a good practice to summarize the findings here, but the repetition of the exact numerical results is not necessary.

 

 

 

Lines 201-202: The authors state that a temperature difference of over 0.6 degrees C could be an indicator of a pathological condition. It is a good point, but the source for this claim should be double-checked to ensure it supports this specific cutoff.

 

Response: ALESSIO. Thank you very much for your contribution. We have added a recent study conducted among healthy patients and patients with brain damage that clarifies and perfectly supports this concept.

 

Lines 211-213: The discussion notes that "descriptively no differences greater than 0.1 degrees C were observed in both sexes, between sides, in the comparison between sexes, mean AT values equal to 0.7 degrees C were obtained." The phrasing is slightly confusing; it should be made clearer that the small differences were found between sides, while a larger difference was found between sexes.

 

Response: Thank you very much for your contribution. We have reviewed and clarified this point with the following statement in line 271: Although descriptive analysis revealed minimal side-to-side differences (≤ 0.1 °C) in both sexes, the comparison between men and women showed a greater mean ΔT of approximately 0.7 °C.

 

Lines 235-236: The authors suggest that a decrease in skin temperature in men is evidence of "peripheral vasoconstriction that redirects blood to the most active muscles." This is an interesting hypothesis, but it is not directly tested. The authors should use more cautious language, such as "may suggest" or "is consistent with."

 

Response: Amended.

 

Lines 278-279: The manuscript mentions a limitation of the study was that assessments took place between 8 am and 5 pm and that this could have led to "inconsistencies in skin temperature among the individuals" due to circadian rhythms. This is a critical point that should be addressed in the methodology section, as it affects the validity of the study.

 

Response: Thank you for your comment. We have removed that sentence, as it was included by mistake. As you can see in lines 183-185, the measurement times are from 8:00 a.m. to 11:30 a.m. We apologize for any inconvenience.

 

Lines 298-300: The conclusion states that IRT is a "valid tool for the measurement, analysis, and quantification of the tissue metabolic response." While the study's results support this, it is important to explicitly state the limitations of using IRT for this purpose, as noted in the discussion (e.g., it does not directly measure deep muscle activity).

 

Response: Amended.

 

Author comment: We appreciate all the comments made on our manuscript, which helped improve it’s quality.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This study investigates the changes in skin temperature of the triceps sural muscle during a maximal fatigue protocol, a relevant topic in sports medicine. The inclusion of both sexes and continuous monitoring during exercise are strengths. However, the manuscript could benefit from improvements in several areas to enhance its scientific rigor and clarity.

 

Abstract:

• The abstract provides a good overview of the study's aims and methods. To strengthen the abstract:
• Include more specific quantitative results, such as the effect sizes (partial eta squared) for the significant findings.
• Briefly mention the limitations of the study (e.g., specific muscle group, lack of direct muscle activity measurement).

 

Introduction:

• The introduction provides a clear rationale for the study.
• Provide a concise definition of "acute muscle fatigue" in the context of this study.
• Expand on the clinical significance of IRT in sports medicine, including specific examples of how it can be used for injury prevention or rehabilitation.
• Clarify the knowledge gap that this study aims to address. The authors mention a lack of consensus on thermoregulatory responses and limitations in previous study designs, but a more focused statement would be beneficial.

 

Materials and Methods:

• Study Design:
• The study design is clearly described. Please, can you explain that the familiarization session was performed 3 days before the development of the stress test? Did the participants continue physical excercise during those days?
• Participants:
• The inclusion and exclusion criteria are well-defined. A table summarizing the key characteristics of the sample (age, BMI, sex distribution, exercise habits) should be included.
• Consider adding information on the participants' training background (e.g., level of physical activity, sports participation).
• Explain how the sample size of 98 participants was determined (e.g., power analysis).
• Equipment and Thermographic Protocols:
• Provide the model number of the Flir E75 camera.
• Justify the choice of 0.98 for the emissivity setting. Include a citation to support the chosen value for skin.
• Specify the method used to ensure constant temperature and humidity in the testing room.
• Clarify the exact positioning of the camera relative to the participants' legs.
• Explain the rationale for taking thermographic images every 5 repetitions. Was this based on previous research or pilot testing?
• How was the "blinded fashion" of image processing ensured? What specific steps were taken to prevent bias?
• Maximum Fatigue Protocol:
• Provide a more detailed description of the step used in the fatigue protocol, including dimensions and material.
• Explain how the constant speed of execution was monitored and enforced.
• Clarify the criteria used to determine when the test was terminated. Was a specific level of pain or discomfort used as a stopping point?
• Justify the decision to conduct testing only in the morning hours (8:00-11:30 AM). Is there evidence that circadian rhythms have a significant impact on skin temperature in the triceps suralis muscle?
• Statistical Analysis:
• Justify the selection of the two-way repeated measures ANOVA. Were the assumptions of ANOVA (e.g., sphericity) met?
• Explain the rationale for including sex, age, ethnicity, dominant side, and BMI as covariates. Were these variables significantly correlated with the outcome measures?
• Report the degrees of freedom for the ANOVA results.

Results:

• Table 1 should include units for all variables (e.g., height in cm, weight in kg).
• Figures 2 and 3: Increase the font size of the axis labels and legends to improve readability.
• Report the confidence intervals for the significant differences found in the post-hoc analysis.
• Provide a more detailed description of the significant differences in the text, including the magnitude and direction of the changes.

Discussion:

• The discussion provides a good interpretation of the findings in relation to previous research.
• Discuss the potential mechanisms underlying the observed differences in thermoregulatory responses between men and women.
• Acknowledge any limitations of the study that may affect the generalizability of the results.
• Suggest specific directions for future research, such as:
• Investigating the thermographic responses of other muscle groups during different types of exercise
• Exploring the use of IRT to monitor muscle fatigue and recovery in athletes
• Combining IRT with other physiological measures (e.g., EMG, blood lactate) to gain a more comprehensive understanding of muscle function

Overall:

• The language used throughout the manuscript is generally clear and concise.
• Ensure that all references are cited correctly and follow the journal's style guidelines.
• The manuscript would benefit from a thorough proofread to correct any grammatical errors or typos.
• Consider that the DOI for the cited articles do not exist. By addressing these comments, the authors can improve the quality and impact of their research.

Author Response

REVIEWER 3

 

This study investigates the changes in skin temperature of the triceps sural muscle during a maximal fatigue protocol, a relevant topic in sports medicine. The inclusion of both sexes and continuous monitoring during exercise are strengths. However, the manuscript could benefit from improvements in several areas to enhance its scientific rigor and clarity.

 We thank the reviewer for their constructive and helpful feedback on our manuscript. We have replied to each specific comment in the section below and have introduced the corresponding edits into the manuscript using Word’s track changes.

Abstract:

• The abstract provides a good overview of the study's aims and methods. To strengthen the abstract:
• Include more specific quantitative results, such as the effect sizes (partial eta squared) for the significant findings.

Response: Amended.

Briefly mention the limitations of the study (e.g., specific muscle group, lack of direct muscle activity measurement).

Response: Amended.

 

Introduction:

• The introduction provides a clear rationale for the study.
• Provide a concise definition of "acute muscle fatigue" in the context of this study.

Response: Amended.

• Expand on the clinical significance of IRT in sports medicine, including specific examples of how it can be used for injury prevention or rehabilitation.

Response: ALESSIO.

• Clarify the knowledge gap that this study aims to address. The authors mention a lack of consensus on thermoregulatory responses and limitations in previous study designs, but a more focused statement would be beneficial.

Response: Thank you for your comment. Following your suggestion, we have modified and added lines 77 to 91.

 

 

Materials and Methods:

• Study Design:
• The study design is clearly described. Please, can you explain that the familiarization session was performed 3 days before the development of the stress test? Did the participants continue physical excercise during those days?

Response: Amended.

 

• Participants:
• The inclusion and exclusion criteria are well-defined. A table summarizing the key characteristics of the sample (age, BMI, sex distribution, exercise habits) should be included.

Response: Thank you for your comment. Table 1 contains that data.

• Consider adding information on the participants' training background (e.g., level of physical activity, sports participation).

Response: Thank you for your comment. Following your suggestion, we have included more information about the sample's level of physical activity.

• Explain how the sample size of 98 participants was determined (e.g., power analysis).

Response: Thank you for your comment. Following your suggestion, we have added a paragraph clarifying the calculation of the sample size. Lines 147-156.

 

Equipment and Thermographic Protocols:

Thank you for this valuable comment. Below, we will explain all the points in more detail.

 

• Provide the model number of the Flir E75 camera. This is the model number: Flir E75
• Justify the choice of 0.98 for the emissivity setting. Include a citation to support the chosen value for skin. Reference 22 explains precisely this issue.
• Specify the method used to ensure constant temperature and humidity in the testing room. The temperature and humidity in the room were monitored and recorded using a digital hygrometer and controlled using the air conditioning units located in the room.
• Clarify the exact positioning of the camera relative to the participants' legs. The camera was positioned in front of the volunteers' legs at an angle of 10º C.
• Explain the rationale for taking thermographic images every 5 repetitions. Was this based on previous research or pilot testing? We could not rely on previous studies as this is the first study to analyze the thermographic response throughout a maximum strength protocol. The choice was dictated by consensus among the authors.
• How was the "blinded fashion" of image processing ensured? What specific steps were taken to prevent bias? Two different researchers analyzed the images at two different times, without contacting each other and without knowing the numerical reference of the images.

 

Maximum Fatigue Protocol:

Thank you for this valuable comment. Below, we will explain all the points in more detail.

 

• Provide a more detailed description of the step used in the fatigue protocol, including dimensions and material. In the maximal gastrocnemius fatigue assessment, participants stood on a 25 cm elevated step with their knees extended, ensuring that the front part of their forefoot (head of the goals) contacted with the step. Line 173.

 

• Explain how the constant speed of execution was monitored and enforced. Patients had to maintain a constant speed of execution, (one second of eccentric phase, dorsiflexion, and one second of concentric phase, plantar flexion, was calculated using a digital stopwatch and verbally indicated by one of the researchers) line 179.

 

• Clarify the criteria used to determine when the test was terminated. Was a specific level of pain or discomfort used as a stopping point? The test was deemed complete when the volunteer was unable to execute further movements, the joint ranges were not adhered to, or the arms were utilized to aid the dorsiflexion phase. Line 185.

 

• Justify the decision to conduct testing only in the morning hours (8:00-11:30 AM). Is there evidence that circadian rhythms have a significant impact on skin temperature in the triceps suralis muscle? The participants took the tests between 8:00 and 11:30 in the morning to minimize the effects of circadian rhythms on body temperature. Previous studies have demonstrated significant circadian rhythmicity in skin temperature. Line 193.

 

 

• Statistical Analysis:
• Justify the selection of the two-way repeated measures ANOVA. Were the assumptions of ANOVA (e.g., sphericity) met?

Response: Thank you for this valuable comment. A two-way repeated measures ANOVA (time × side) was selected because the experimental design involved repeated measurements of temperature at four intensity points (25%, 50%, 75%, and 100% of total effort) on both limbs of each participant. This model was appropriate for evaluating the intra-subject effects (time and side) and their interaction.

 

Before performing the analysis, the assumptions of normality and sphericity were checked. The Shapiro-Wilk test confirmed the normal distribution of the residuals, and Mauchly's sphericity test showed that the assumption was met (p > 0.05). When necessary, the Greenhouse-Geisser correction was applied to adjust the degrees of freedom.

• Explain the rationale for including sex, age, ethnicity, dominant side, and BMI as covariates. Were these variables significantly correlated with the outcome measures?

Response: The inclusion of sex, age, ethnicity, and dominant side as between-subjects factors, and BMI and total number of repetitions as covariates, was based on their potential physiological influence on skin temperature regulation and fatigue development. Although these variables were included in the initial model to control for possible confounding effects, none of them showed significant correlations (p > 0.05) with the main outcome variable (skin temperature).

• Report the degrees of freedom for the ANOVA results.

Time: df 4; 4 × (98−1) = 388.

Side: df 1; 98−1 = 97.

Time × Side: df 4; 4 × (98−1) = 388.

 

Results:

• Table 1 should include units for all variables (e.g., height in cm, weight in kg).

Response: Amended.

• Figures 2 and 3: Increase the font size of the axis labels and legends to improve readability.

• Response: Amended.

• Report the confidence intervals for the significant differences found in the post-hoc analysis.

Response: Amended.

• Provide a more detailed description of the significant differences in the text, including the magnitude and direction of the changes.

Response: Amended.

 

Discussion:

• The discussion provides a good interpretation of the findings in relation to previous research.
• Discuss the potential mechanisms underlying the observed differences in thermoregulatory responses between men and women.

Response: Thank you for your comment. Following your suggestion, I have added a paragraph to clarify the differences in thermoregulatory responses between men and women.

• Acknowledge any limitations of the study that may affect the generalizability of the results.

Response: Thank you for your comment. We already have a section that outlines the limitations of this research.

• Suggest specific directions for future research, such as:
• Investigating the thermographic responses of other muscle groups during different types of exercise.
• Exploring the use of IRT to monitor muscle fatigue and recovery in athletes.
• Combining IRT with other physiological measures (e.g., EMG, blood lactate) to gain a more comprehensive understanding of muscle function.

Response: Amended.

 

 

Author comment: We appreciate all the comments made on our manuscript, which helped improve it’s quality.

Author Response File: Author Response.pdf