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Thank you for carefully addressing all the raised points in your revision and for clearly adding the literature search dates in your manuscript. I am pleased to confirm that your article is now accepted for publication. Congratulations on your excellent work!
[# PeerJ Staff Note - this decision was reviewed and approved by Mike Climstein, a PeerJ Section Editor covering this Section #]
Thank you for your careful and detailed revision. You have clarified the study count, corrected formatting issues, and improved the overall presentation and readability of the manuscript. These revisions have strengthened the clarity and consistency of the work.
Before acceptance, please can you sneure that you include the dates of your search(es) in the manuscript.
There are some minor edits in the attached file that you should also address.
Thank you for your detailed revision and responses. The manuscript has improved in many aspects; however, there remain points that need clarification before we can proceed further:
1) There is an inconsistency in the number of included studies: 144 and 117 both numbers are mentioned in your rebuttal letter, while 117 appears in the revised manuscript. Please clarify and ensure that the reported number is consistent and correct throughout the manuscript and responses.
2) Please check the line numbering, as it is discontinuous in places.
3) Several grammatical and stylistic errors remain; we encourage you to carefully proofread the text to improve readability and presentation.
The reviewer has identified a number of outstanding issues that must be fully addressed if the manuscript is to be considered any further.
The manuscript lacks in-depth analysis and raises concerns regarding reproducibility.
The authors did not report the exact number of studies included in the present review. Additionally, they did not provide a clear rationale for the selection of the keywords used in this study. This severely affects the reproducibility of the manuscript.
Most of the manuscript merely repeats definitions from previous research without offering any critical perspectives or original insights from the authors themselves.
Line 20: Please remove all citations from the abstract, as abstracts typically should not include references.
Line 20: The terms “exercise fatigue” and “exercise-induced fatigue” are used inconsistently throughout the text. I recommend unifying the terminology by replacing “exercise fatigue” with “exercise-induced fatigue” not only in this part but consistently throughout the entire manuscript for clarity and precision.
Line 81-85: What is the rationale for selecting these specific keywords and phrases? Additionally, how can you ensure that the chosen search terms are comprehensive and valid for capturing all relevant studies?
Line 85-87: How many studies were ultimately included in the analysis? Please clarify this point, as the lack of this information raises concerns about the reproducibility of the review.
Line 128-: The latter part (from chapter 4) of the manuscript lacks a professional structure and sufficient reference support. Many statements are presented without appropriate citations, which questions the scientific rigor of the work.
Line 300: There are still too many abbreviations used throughout the manuscript, which makes the text difficult to follow.
**PeerJ Staff Note:** Please ensure that all review, editorial, and staff comments are addressed in a response letter and that any edits or clarifications mentioned in the letter are also inserted into the revised manuscript where appropriate.
**Language Note:** PeerJ staff have identified that the English language needs to be improved. When you prepare your next revision, please either (i) have a colleague who is proficient in English and familiar with the subject matter review your manuscript, or (ii) contact a professional editing service to review your manuscript. PeerJ can provide language editing services - you can contact us at [email protected] for pricing (be sure to provide your manuscript number and title). – PeerJ Staff
This manuscript discusses the underlying mechanisms of exercise-induced fatigue and several conventional biomarkers. It is generally well-structured. However, much of the content merely reiterates previous definitions and studies without providing clear insights or critical opinions from the authors. The authors primarily summarize existing references without offering any in-depth re-analysis or synthesis. As a result, the manuscript reads more like a traditional narrative review rather than a systematic review.
no comment
no comment
Detailed comments
Line 18: Do you mean "exercise-induced fatigue"? It's not clear whether you are referring to fatigue caused by exercise or a specific method to improve fatigue tolerance. I suggest changing "exercise fatigue" to "exercise-induced fatigue" for clarity.
Line 21: You also mentioned skeletal muscle in the following text, so I recommend changing "nervous system" and "skeletal muscles" to "neuromuscular system" for consistency and clarity.
Line 28: "Biomarker" appears to refer to the measurements mentioned in the previous text. However, in this context, I believe you intended to refer to "fatigue-related physiological responses" rather than biomarkers specifically. Please clarify and revise accordingly.
Line 35: I did not find any references cited in the Introduction. While most of the statements may be considered common knowledge for experts in related fields, including references would be helpful for readers who are less familiar with fatigue-related topics.
Line 40-43: Several fatigue-related parameters are mentioned in this section. I recommend providing appropriate references to support these claims and enhance the scientific rigor of the manuscript.
Line 74: What do you mean by "R&D trend"? Please clarify the term, as it may not be immediately clear to all readers.
Line 89-93: Please provide references to support the definitions of central and peripheral fatigue, as these are key concepts in the manuscript and should be grounded in established literature.
Line 123: This section contains too many abbreviations, which makes it difficult to read. Some of the abbreviations are only used once and may not be necessary. I recommend reducing their use to improve clarity.
Line 128: Section 4.1 primarily discusses well-known mechanisms of energy metabolism. I recommend significantly simplifying this part, as the content is largely introductory and may not contribute new insights to the manuscript.
Line 156-157: Once again, references are missing throughout the manuscript. I strongly recommend a thorough review to ensure that all key statements and definitions are properly supported by citations.
Line 191: The increase in blood lactate concentration is primarily induced by muscle contractions. Furthermore, it is well established that this increase is largely attributed to the activation of fast-twitch muscle fibers, which are characterized by high force production but low fatigue resistance (see, for example, Sánchez-Medina L, González-Badillo JJ. Velocity loss as an indicator of neuromuscular fatigue during resistance training. Med Sci Sports Exerc. 2011 Sep;43(9):1725–34. doi:10.1249/MSS.0b013e318213f880). I recommend adding a brief clarification regarding the physiological relationship between lactic acid accumulation and muscle contraction to improve clarity and completeness.
Line 245: To my knowledge, CK is primarily used as a marker of muscle damage. Please clarify the relationship between CK and muscle fatigue.
Line 415: Section 4 presents numerous definitions of physiological processes during exercise; however, it lacks discussion on why these processes are mentioned and how they relate to fatigue. I recommend significantly simplifying this section and focusing more on the relevance of each physiological mechanism to the manuscript’s central theme.
Line 482-483: Please provide specific scenarios or practical applications of these new blood sampling techniques in the context of fatigue assessment, rather than only offering definitions. If no practical examples currently exist, I suggest adding a clarification to that effect. As currently presented, the description makes it difficult for readers to visualize the actual differences between conventional and new blood sampling techniques.
Line 493: Urine- and saliva-based fatigue quantification methods are commonly used as non-invasive markers in sports and other practical settings. I recommend including a discussion on potential approaches to improve their measurement precision, as this would enhance the practical relevance and scientific depth of the manuscript.
Line 510: Techniques such as microneedle-based sampling also rely on blood collection. Therefore, I suggest integrating this section with the earlier discussion on blood testing techniques to improve coherence and avoid redundancy.
Line 540: You emphasized the importance of establishing a standardized sampling protocol; however, the preceding text and the title of this section mainly focus on new sampling techniques. This statement appears inconsistent with the section’s primary content. I recommend revising this part to better align with the preceding discussion or providing a clearer transition to justify the shift in focus.
Line 559: You mentioned the significance of fatigue assessment, but the manuscript would benefit from a more explicit discussion on potential solutions for assessing fatigue in individual users. For example, ease of use is a critical factor in practical fatigue assessment, and subjective measures such as the RPE may serve as an effective indirect marker of muscle fatigue in such contexts (see Zhao H, Kurokawa T, Tajima M, Liu Z, Okada J. Perceived exertion reflects fatigue conditions during power-aimed resistance training. Int J Sports Med. 2025 Mar 25. doi: 10.1055/a-2545-5403).
Figure: The figure legends are too simple. Please provide the full names of the abbreviations used in the figures.
Figure 4: Figure 4 is difficult to understand and appears to largely repeat the content presented in Section 5. I recommend simplifying or removing this figure to avoid redundancy and improve the overall clarity of the manuscript.
This review aims to summarize the latest research on biomarkers associated with exercise fatigue, as well as recent advancements in the detection of these biomarkers and the application to sports medicine. This is a worthwhile and timely topic, particularly the inclusion of detection methods and application. However, the review has several critical weaknesses.
Critical weaknesses in basic reporting include:
- Lack of any references in the Introduction, resulting in no support for the foundational claims of the review.
- Lack of professional structure. For example, the Introduction has many 'purpose' statements throughout that are not all aligned or adequately justified. There is a 'conclusion' statement in the middle of the Introduction. The bulk of the review is the definition of biomarkers of interest, accounting for more material than that addressing the purpose statements.
Critical weakness in study design:
- The type of literature review is not stated or defined (e.g. systematic, scoping, etc.).
- Reporting methods are insufficient. All searched databases should be listed, not just examples. All utilized keywords should be listed. No definitions provided for 'high-quality research' and 'recent years'. Replication of this search is impossible, and the quality and comprehensiveness of the included literature cannot be assessed.
Critical weakness in validity:
- Search cannot be replicated.
- While the overall purpose is a worthwhile and interesting topic, the additional and more specific purpose statements are often lacking sufficient support and are inconsistently addressed throughout the results.
No comment.
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