Combining HIIT Plus Cognitive Task Increased Mental Fatigue but Not Physical Workload in Tennis Players

Round 1

Reviewer 1 Report

Abstract

The abstract does not clearly state the research objective. It should explicitly mention what the authors aimed to investigate in this study, such as the specific aspects of mental and physical fatigue, and the potential impact of combining HIIT with a cognitive task.

 

The abstract briefly mentions that the subjective feelings of physical exertion increased due to mental fatigue but did not affect the physical workload during HIIT. However, it does not elaborate on the potential implications or practical significance of these findings. It would be beneficial to discuss how these results could be applied in practice, such as informing training protocols or strategies for managing mental fatigue in sports performance.

 

Introduction

The introduction contains several long and complex sentences that can be challenging to follow. The authors should strive for clearer and more concise writing to enhance readability.

 

While the introduction provides a comprehensive overview of previous research on mental fatigue and fatigability in sports, it would be helpful for the authors to explicitly state the research gap or the specific problem they aim to address in this study. What is missing from the existing literature? This will help set the context and rationale for the current study.

 

The authors mention that the study will be conducted on a sample of tennis practitioners, but they do not provide a clear rationale for this choice. Why is the tennis population specifically relevant to this study? Are there any unique characteristics of tennis that make it an ideal sport for investigating the effects of mental fatigue on HIIT? The authors should provide a justification for their sample selection to strengthen the study's relevance and generalizability.

 

The authors briefly mention their hypothesis that mental fatigue will negatively influence the physical performance of tennis practitioners during HIIT. However, the hypothesis could be stated more precisely and explicitly. It should also be clearly linked to the existing literature. Additionally, the authors should specify the specific performance measures they expect to be affected by mental fatigue.

 

It would be helpful for the authors to briefly discuss the potential practical implications of their research findings. How might the results of this study contribute to the understanding of mental fatigue in sports and its impact on HIIT performance? Are there any implications for coaches, trainers, or athletes in terms of training strategies, performance optimization, or mental health management? Including a brief discussion on the practical implications can add value to the research.

Methodology

Sample size and representativeness: The sample size of 32 tennis players may be relatively small, and it is important to consider whether this adequately represents the larger population of tennis players or if it limits the generalizability of the findings.

 

Discussion

The authors briefly mention that the results suggest important pre-indices and practical applications, but they do not clearly elaborate on these implications. It would be helpful for the authors to discuss the practical implications of their findings in more detail. How can the results be applied in the context of sports training or performance? How can coaches and practitioners use this information to optimize training programs and manage mental fatigue? Providing specific examples and recommendations will enhance the practical relevance of the study.

 

Discuss the limitations in more depth: While the authors mention some limitations of the study, such as the use of a specific sport (tennis practitioners) and the lack of individual cognitive performance data, they do not provide a thorough discussion of these limitations. It is important for the authors to address the implications of these limitations on the interpretation of the results. How do these limitations affect the generalizability of the findings? What potential biases or confounding factors could arise from these limitations? By acknowledging and discussing the limitations more extensively, the authors can provide a more balanced view of the study's scope and validity.

 

The authors report that there were no significant differences in physical efforts quantified with mean and maximum heart rate (HR), speed, and other performance measures between the mentally fatiguing and control conditions. However, the authors do not thoroughly discuss the potential reasons for these non-significant findings. It would be valuable for the authors to speculate on possible explanations for the lack of differences, considering factors such as the nature of the HIIT protocol, the duration of the mental fatigue induction, and individual variations in response to mental fatigue. Providing insights into these factors can help readers better understand the study's outcomes.

Author Response

Thank you for all your constructive and valuable suggestions. We have incorporated all your comments and we truly believe that the quality of the manuscript has been significantly increased.

The abstract does not clearly state the research objective. It should explicitly mention what the authors aimed to investigate in this study, such as the specific aspects of mental and physical fatigue, and the potential impact of combining HIIT with a cognitive task.

 Authors´response: It was modified.

 

The abstract briefly mentions that the subjective feelings of physical exertion increased due to mental fatigue but did not affect the physical workload during HIIT. However, it does not elaborate on the potential implications or practical significance of these findings. It would be beneficial to discuss how these results could be applied in practice, such as informing training protocols or strategies for managing mental fatigue in sports performance.

 Authors´response: It was included.

Introduction

The introduction contains several long and complex sentences that can be challenging to follow. The authors should strive for clearer and more concise writing to enhance readability.

Authors´response: It was corrected.

While the introduction provides a comprehensive overview of previous research on mental fatigue and fatigability in sports, it would be helpful for the authors to explicitly state the research gap or the specific problem they aim to address in this study. What is missing from the existing literature? This will help set the context and rationale for the current study.

Authors´response: Thank you for your comment. It has been included by the end of the introduction.

 

The authors mention that the study will be conducted on a sample of tennis practitioners, but they do not provide a clear rationale for this choice. Why is the tennis population specifically relevant to this study? Are there any unique characteristics of tennis that make it an ideal sport for investigating the effects of mental fatigue on HIIT? The authors should provide a justification for their sample selection to strengthen the study's relevance and generalizability.

Authors´response: Thank you for your comment. It has been included by the end of the introduction.

 

The authors briefly mention their hypothesis that mental fatigue will negatively influence the physical performance of tennis practitioners during HIIT. However, the hypothesis could be stated more precisely and explicitly. It should also be clearly linked to the existing literature. Additionally, the authors should specify the specific performance measures they expect to be affected by mental fatigue.

 Authors´response: It was corrected.

 

It would be helpful for the authors to briefly discuss the potential practical implications of their research findings. How might the results of this study contribute to the understanding of mental fatigue in sports and its impact on HIIT performance? Are there any implications for coaches, trainers, or athletes in terms of training strategies, performance optimization, or mental health management? Including a brief discussion on the practical implications can add value to the research.

Authors´response: It was included in the discussion.

 

Methodology

Sample size and representativeness: The sample size of 32 tennis players may be relatively small, and it is important to consider whether this adequately represents the larger population of tennis players or if it limits the generalizability of the findings.

Authors´response:  It was included as a limitation of the study.

 

Discussion

The authors briefly mention that the results suggest important pre-indices and practical applications, but they do not clearly elaborate on these implications. It would be helpful for the authors to discuss the practical implications of their findings in more detail. How can the results be applied in the context of sports training or performance? How can coaches and practitioners use this information to optimize training programs and manage mental fatigue? Providing specific examples and recommendations will enhance the practical relevance of the study.

Authors´response:  It was developed.

 

Discuss the limitations in more depth: While the authors mention some limitations of the study, such as the use of a specific sport (tennis practitioners) and the lack of individual cognitive performance data, they do not provide a thorough discussion of these limitations. It is important for the authors to address the implications of these limitations on the interpretation of the results. How do these limitations affect the generalizability of the findings? What potential biases or confounding factors could arise from these limitations? By acknowledging and discussing the limitations more extensively, the authors can provide a more balanced view of the study's scope and validity.

Authors´response:   It was discussed.

The authors report that there were no significant differences in physical efforts quantified with mean and maximum heart rate (HR), speed, and other performance measures between the mentally fatiguing and control conditions. However, the authors do not thoroughly discuss the potential reasons for these non-significant findings. It would be valuable for the authors to speculate on possible explanations for the lack of differences, considering factors such as the nature of the HIIT protocol, the duration of the mental fatigue induction, and individual variations in response to mental fatigue. Providing insights into these factors can help readers better understand the study's outcomes.

Authors´response:  It was discussed.

Reviewer 2 Report

This research can be valuable if the lot of subjects is larger.

The subject of this research is widely debated by the tennis players' community.

Good luck

I found some spelling mistakes that may or may not be fixed. It depends on how the authors thought

Author Response

This research can be valuable if the lot of subjects is larger.

The subject of this research is widely debated by the tennis players' community.

Good luck

Comments on the Quality of English Language

I found some spelling mistakes that may or may not be fixed. It depends on how the authors thought.

Authors´ response: Thank you for your positive feedback. We have reviewed the document in order to correct some typos and mistakes.

 

Reviewer 3 Report

Thank you for the opportunity to review this manuscript.

The authors provide a nice study comparing HIIT and HIIT combined with cognitive task effects on mental fatigue and physical workload in tennis players. The information is presented in an organized way but the more precise description of HIIT training protocol would be helpful to readers. I would like to suggest some areas to be improved in this manuscript:

 

Abstract:

-       Abbreviation HIIT not explained.

 

Introduction:

-       Page 2, line 63. Authors explain that “HRV is a noninvasive tool <…>”, but actually it is not a tool.

-       Page 2, line 84-85. Authors mention “tennis service”, but the actual word used in original reference is tennis serve.

-       Page 2, lines 93-97. English is very difficult to understand and the main idea of the paragraph is not clear. Was the aim of the study to investigate the effect of mental fatigue on HIIT or on other variables? To note, the study aim is mentioned in 3 different places in the manuscript, and all are formulated differently. Language and logics should be improved.

-       Page 2, line 96. If hypothesis 1 is mentioned, where are the 2 or 3 hypotheses?

 

Materials and methods:

-       More details about the participants are missing (level of professionalism? Years of practice?).

-       Groups should be described in section 2.1.

-       Page 3, line 101. Units of mean age should be indicated (21.40 ± 1.52 years).

-       From my point of view, they should give more details about the HIIT trainings performed, as the figure is scarce. What do they mean by 12 repetitions of 30 seconds of push-ups, squats and lateral displacements with other 30 seconds of rest”? How long was the physical load in total? It is not clear, how many cognitive task breaks were in total, since they mention only 3 times per training, but if I calculate correctly there should have been 12x3? Please describe it in details.

-       If participants were wearing Polar devices continuously, what was the intensity of HIIT training?

-       Figure 1. Abbreviations not explained.

-       Study organization is not prescribed thoroughly. Which time of the day (morning of evening hours) the study was carried out? Did all the participants perform study at the same time of the day? How did you control the intensity of the training? Did the participants consume caffeine of other stimulants before study?

-       Page 5, line 182. It is mentioned about supplementary files, but they were not provided for reviewer.

 

Results:

-       Page 5, line 201. <…> HIIT without cognitive load (p < .001),”, but in the Table 1 p-value is equal to .001.

-       Page 5, line 202. Term “external physical load” is confusing, since it has not been previously described in any ways. Then, what is internal physical load? Authors should be more specific in this explanation of results.

-       Table 1 and Table 2, no measurement units are provided for variables.

-       Page 5, line 214. “Table 2 shows the evolution of subjective (obtained from the Hooper and Mackinnon wellness questionnaire and the VAS for mental fatigue) and the RMSSD from pre- to post- each training.” It seems that the sentence is missing some words; on the other hand the English of result section is quite difficult to understand.

-       Table 2. If authors mention subjective and physiological indicators of mental fatigue in the title of the table, then I would strongly recommend to clearly marking out them in the table.

 

 

Discussion:

-       Page 6, lines 232-233. The aim of the study seems to miss some words (the effect on what variables?).

-       Page 6, lines 253. What authors mean by the term “psychobiological indicators of physical performance? It was not previously explained.

-       Page 6, paragraph 2. Authors discuss on the mood state, but the intrinsic motivation is not exactly the same as the mood state. Need to improve the discussion.

-       Overall, the discussion part is missing considerations about the duration of cognitive load. Maybe short bouts (30 s) of cognitive task were not enough to evoke mental fatigue?

 

Conclusions:

-       English very difficult to understand/incomprehensible.

-       Page 8, lines 324-325, what is the word “incon-groups”?

-       The conclusions of the study are weak and do not bring anything new to the scientific community.

Comments for author File: Comments.pdf

At some parts of the manuscript English is very difficult to understand and the grammar is incorrect. From my point of view, moderate editing of English language is needed.

Author Response

Response: Thanks for your positive comments to our work. Also, thanks for your efforts to allow us to improve the quality of the manuscript. We have tried to improve all your suggestions. We indicated all the changes in the manuscripts, using a red color to highlight all of them.

 

Abstract:

− Abbreviation HIIT not explained.

 

Response: HIIT is the abbreviation of the previous High-Intensity Interval Training. We have indicated.

 

Introduction:

− Page 2, line 63. Authors explain that “HRV is a noninvasive tool <…>”, but actually it is not a tool.

 

Response: It has been changed by “biomarker of fatigue”.

 

− Page 2, line 84-85. Authors mention “tennis service”, but the actual word used in original reference is tennis serve.

 

Response: Thanks! It was changed.

 

− Page 2, lines 93-97. English is very difficult to understand and the main idea of the paragraph is not clear.

Was the aim of the study to investigate the effect of mental fatigue on HIIT or on other variables? To note, the study aim is mentioned in 3 different places in the manuscript, and all are formulated differently.

Language and logics should be improved.

 

Response:

 

− Page 2, line 96. If hypothesis 1 is mentioned, where are the 2 or 3 hypotheses?

 

Response: Ok, it was clarify.

 

Materials and methods:

− More details about the participants are missing (level of professionalism? Years of practice?).

 

Response: Included.

 

− Groups should be described in section 2.1.

 

Response: Done

 

− Page 3, line 101. Units of mean age should be indicated (21.40 ± 1.52 years).

 

Response: Ok, it has been included.

 

− From my point of view, they should give more details about the HIIT trainings performed, as the figure is scarce. What do they mean by 12 repetitions of 30 seconds of push-ups, squats and lateral displacements with other 30 seconds of rest”? How long was the physical load in total? It is not clear, how many cognitive task breaks were in total, since they mention only 3 times per training, but if I calculate correctly there should have been 12x3? Please describe it in details.

 

Response: Thank you for your comments. You were totally right that in the description of the session and in the figure as well there were some confusions. We have amended the information.

 

− If participants were wearing Polar devices continuously, what was the intensity of HIIT training?

 

Response: The intensity of all whole training session (mean and maximum heart rate) could be seen in Table 1.

 

− Figure 1. Abbreviations not explained.

 

Response: Thanks for this suggestion. We have included it in notes.

 

− Study organization is not prescribed thoroughly. Which time of the day (morning of evening hours) the study was carried out? Did all the participants perform study at the same time of the day? How did you control the intensity of the training? Did the participants consume caffeine of other stimulants before study?

 

Response: Thank you for your comment. These details have been included in the method section.

 

− Page 5, line 182. It is mentioned about supplementary files, but they were not provided for reviewer.

 

Response: Thank you for advising us about this mistake. We have added the supplementary file.

 

Results:

− Page 5, line 201. <…> HIIT without cognitive load (p < .001),”, but in the Table 1 p-value is equal to .001.

 

Response: Thanks! Changed in the text.

 

− Page 5, line 202. Term “external physical load” is confusing, since it has not been previously described in any ways. Then, what is internal physical load? Authors should be more specific in this explanation of results.

 

Response: It has been clarified in the method section. “Heart rate variables refer to internal physical load, meanwhile, speed variables refer to external physical load”

 

− Table 1 and Table 2, no measurement units are provided for variables.

 

Response: Thanks! It has been included in both tables.

 

− Page 5, line 214. “Table 2 shows the evolution of subjective (obtained from the Hooper and Mackinnon wellness questionnaire and the VAS for mental fatigue) and the RMSSD from pre- to post- each training.” It seems that the sentence is missing some words; on the other hand the English of result section is quite difficult to understand.

 

Response: Thank you for your constructive suggestion. We have tried to clarify this section.

 

− Table 2. If authors mention subjective and physiological indicators of mental fatigue in the title of the table, then I would strongly recommend to clearly marking out them in the table.

 

Response: Done.

 

Discussion:

− Page 6, lines 232-233. The aim of the study seems to miss some words (the effect on what variables?).

 

Response: It has been changed to clarify.

 

− Page 6, lines 253. What authors mean by the term “psychobiological indicators of physical performance? It was not previously explained.

 

Response: It has been changed and clarified as: “objective (i.e., heart rate and speed variables)”.

 

− Page 6, paragraph 2. Authors discuss on the mood state, but the intrinsic motivation is not exactly the same as the mood state. Need to improve the discussion.

 

Response: You were totally right. We have removed this sentence since it is not the same and then we cannot interpolate to our investigation.

 

− Overall, the discussion part is missing considerations about the duration of cognitive load. Maybe short bouts (30 s) of cognitive task were not enough to evoke mental fatigue?

 

Response: Really, the markers of mental fatigue indicated that these short bouts significantly increase the feelings of mental fatigue of the participants. We have remarked it in the discussion.

 

Conclusions:

− English very difficult to understand/incomprehensible.

 

Response: A native English speaker had help us to re-writte this part.

 

− Page 8, lines 324-325, what is the word “incon-groups”?

 

Response: It was a mistake. It has been changed.

 

− The conclusions of the study are weak and do not bring anything new to the scientific community.

Response: We have re-written.

 

Round 2

Reviewer 1 Report

Thank you for your careful revision