Effects of High-Intensity Interval Training on Functional Fitness in Older Adults

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Clear and relevant manuscript.

• What is the main question addressed by the research?

Under a randomized controlled trial, this manuscript examines whether high-intensity interval training could be an effective strategy to enhance functional fitness in older adults.

 

• Do you consider the topic original or relevant to the field? Does it address a specific gap in the field? Please also explain why this is/ is not the case.

The relevance of this manuscript lies in its design (randomized controlled trial), sufficient sample size, and the method (High-Intensity Interval Training in older adults). Fewer manuscripts with these features are. 

 

• What does it add to the subject area compared with other published material?

This manuscript emphasizes the need for longer and more systematic exercise to maintain the health of older adults.

 

• What specific improvements should the authors consider regarding the methodology?

The main limitation of this manuscript is the fault in controlling the intensity of the exercise. The authors must add this information to the results.

 

• Are the conclusions consistent with the evidence and arguments presented and do they address the main question posed? Please also explain why this is/is not the case.

The conclusions are clear and consistent with the evidence and arguments presented,

 

• Are the references appropriate?

Some references are outdated, and others could be excluded because they are Internet sources.

 

• Any additional comments on the tables and figures.

 

Recommendations:

Correct language: Lines 71-73

Figure 1. Remove the phrase “give reasons” and fix the last box on the left: n=0.

Add a title and caption to the last figure.

The last figure is clear and illustrative. However, in addition to the figure, include a table with results (means, medians, SD, 95% CI, effect size). This will make it easier to analyze the results and could increase the chances of your manuscript being cited.

After listing the limitations, include the strengths of your study.

 

Author Response

Response to Reviewer 1 – Targeted Points

We thank the reviewer for the valuable suggestions, which helped us improve the quality and clarity of the manuscript. Please find below our specific responses to the requested points.

 

1. What specific improvements should the authors consider regarding the methodology?

“The main limitation of this manuscript is the fault in controlling the intensity of the exercise. The authors must add this information to the results.”

Response:

We agree with the reviewer and have addressed this concern by adding a description of the perceived exercise intensity in the Results section. Specifically, we included weekly monitoring data using the Borg Rating of Perceived Exertion (RPE) scale, which confirmed that participants performed the high-intensity intervals within the target range:

“Participants in the HIIT group consistently reported values between 13 and 16 (mean: 14.2 ± 1.1) during high-intensity intervals, and between 9 and 11 (mean: 10.0 ± 0.9) during active recovery phases.”

This confirms that exercise intensity was adequately monitored and aligned with HIIT protocols.

 

2. Are the references appropriate?

“Some references are outdated, and others could be excluded because they are Internet sources.”

Response:

Thank you for the observation. We reviewed and updated the reference list. Outdated references were replaced with more recent, peer-reviewed publications. Additionally, internet-based sources were removed or substituted by scientific literature where appropriate.

 

3. Any additional comments on the tables and figures.

• Line correction (Lines 71–73):

The language in these lines has been corrected for clarity and grammar.

• Figure 1:

The phrase “give reasons” was removed, and the last box on the left now reads “n = 0” as suggested.

• Final figure:

A title and caption were added to the final figure for clarity and consistency.

• Table with statistical results:

We have included a new Table 2, which reports descriptive statistics for each outcome variable, including means, medians, standard deviations, 95% confidence intervals, and Relative Treatment Effects (RTE). This enhances the transparency and reproducibility of the findings and aligns with the reviewer’s suggestion to facilitate future citations and meta-analyses.

 

4. Strengths of the study

“After listing the limitations, include the strengths of your study.”

Response:

As recommended, we have added a paragraph highlighting the strengths of our study in the Discussion section, including:

• The extended 65-week duration of the intervention,
• The use of a randomized controlled trial design,
• The inclusion of older adults from the community, enhancing ecological validity,
• The application of robust nonparametric longitudinal models (Brunner-Langer),
• And the intensity monitoring using the Borg RPE scale, ensuring fidelity to the HIIT protocol.

Reviewer 2 Report

Comments and Suggestions for Authors

I first would like to congratulate the author for this interesting study about the effects of high-intensity interval training on functional fitness in older adults. It’s a considerable effort from the researchers and the materials involved.

It’s well written and follows the IMRAD design and describes adequately the content of the research protocol. The background of the study is clear, but it doesn’t point out the need for further research in this field. The methods and findings are well structured, but they need some improvements in my opinion. The statistical techniques are well justified. Moreover, the results are discussed in an adequate manner.

After reading I’d like to suggest some adjustments, some improvements, and corrections.

I would suggest adjusting the abstract to fit the journal's guidelines: a single paragraph of about 200 words maximum, without headings.

On line 72, there is likely a typo.

While the introduction is generally well-structured, the innovative nature of this study isn't clearly stated. After describing the main benefits of HIIT (lines 63-71) and the literature gap (lines 72-78), I would suggest explicitly highlighting the original contribution of this study to scientific research on this topic.

It's recommended to justify the text throughout the entire manuscript.

Were the inclusion criteria chosen based on other studies? It would be good to specify this.

On line 107, it's stated that an inclusion criterion is being over 60 years old, while on line 113, an exclusion criterion is being under 65 years old. I suggest clarifying this discrepancy.

How was the sample recruited? What type of sampling was performed? This should be specified.

On line 129, it says "which studies?" I suggest citing the previous studies.

In my opinion, the paragraph (lines 126–134) is not very clear. How was the sample size calculated based on the primary outcome? This needs to be specified.

I would suggest aligning the descriptions of the assessment tests. The Senior Fitness Test is described quite briefly, while the handgrip test is more detailed. I recommend describing the other tests in equal detail. Additionally, please specify the number of trials conducted for each test.

On line 158, "physical capacities" should be replaced with "physical fitness components."

I suggest the authors explain how the activity was individually adapted and personalized, even though the activities were done in a group (on lines 215-217).

How did the authors evaluate adherence to the project? Was a minimum participation frequency established for inclusion in the study? This should be clarified.

I would suggest describing and including RTE in the statistical analysis as well (RTE is only mentioned for the first time on line 279).

The objectives stated on lines 345-347 are slightly different from those in the introduction. In general, I would suggest making the innovative elements of this work explicit in the introduction compared to existing scientific studies (for example, focusing on the medium- to long-term effects of HIIT on physical efficiency components).

Furthermore, the HIIT protocol involves a significant increase in heart rate. Was this aspect taken into consideration by the authors? If so, how was heart rate monitored during the activities? This topic needs to be clarified.

The conclusions are quite modest. As mentioned earlier, I suggest presenting the study's most original results concisely.

Please, revised the bibliographic citation according to journal’s guidelines.

Major revision are required.

Author Response

1. I would suggest adjusting the abstract to fit the journal's guidelines: a single paragraph of about 200 words maximum, without headings.

Thank you for your suggestion regarding the abstract formatting. Following your recommendation, we revised the abstract to comply with the journal’s guidelines. It is now written as a single paragraph without headings and limited to 188 words, while maintaining a clear structure that includes the background, methods, results, and conclusions of the study.

 

2. While the introduction is generally well-structured, the innovative nature of this study isn’t clearly stated. After describing the main benefits of HIIT (lines 63–71) and the literature gap (lines 72–78), I would suggest explicitly highlighting the original contribution of this study to scientific research on this topic.

Author Response:

We thank the reviewer for this valuable suggestion. In response, we have revised the end of the second paragraph of the Introduction to explicitly highlight the innovative aspects of our study. We now emphasize the long duration of the intervention (65 weeks), the use of field-based assessments of functional fitness, and the application of a nonparametric longitudinal model. This addition clarifies the original contribution and real-world applicability of our trial in community-dwelling older adults. The revised passage reads as follows:

“To address this gap, this study presents one of the longest randomized controlled trials (65 weeks) to examine the effects of HIIT on multiple domains of functional fitness in community-dwelling older adults. By combining long-term follow-up, field-based functional assessments, and nonparametric longitudinal analysis, this research offers an original contribution to understanding the real-world applicability and sustainability of HIIT interventions in aging populations.”

 

3. It’s recommended to justify the text throughout the entire manuscript.

Author Response:

Thank you for the observation. We have now applied full justification to all text paragraphs throughout the manuscript to enhance readability and ensure consistency with academic formatting standards.

 

4. Were the inclusion criteria chosen based on other studies? It would be good to specify this.

 

Author Response:

Thank you for pointing this out. We have now clarified in the Methods section that the inclusion criteria—community-dwelling older adults aged 60 years or above, physically independent, and free from contraindications to exercise—were established based on previous randomized controlled trials involving HIIT protocols in older populations [References 7–9]. This addition helps to contextualize the eligibility parameters and align them with existing literature.

 

5. On line 107, it's stated that an inclusion criterion is being over 60 years old, while on line 113, an exclusion criterion is being under 65 years old. I suggest clarifying this discrepancy.

Author Response:

Thank you for this observation. We clarified the discrepancy between the inclusion and exclusion criteria by standardizing the age threshold to 65 years across both. The inclusion criteria have been revised accordingly to reflect this adjustment and maintain internal consistency.

 

6. How was the sample recruited? What type of sampling was performed? This should be specified.

Author Response:

Thank you for your observation. We have now specified how the sample was recruited. Participants were recruited through non-probabilistic convenience sampling from local community centers and senior groups in Bragança, Portugal. Recruitment was conducted via informational flyers, social media announcements, and direct invitations during health promotion events. This information has been added to the Methods section under “Sample.

 

7. On line 129, it says "which studies?" I suggest citing the previous studies.

Author Response:

We appreciate the reviewer’s attention to the sample size justification. The clinically relevant difference of 15 steps and the estimated standard deviation of 18 steps were based on previous findings reported in the systematic review and meta-analysis by Stern et al. [7], which investigated functional outcomes in older adults undergoing physical exercise interventions. This reference has now been explicitly cited in the text to clarify the source of the parameters used.

 

8. In my opinion, the paragraph (lines 126–134) is not very clear. How was the sample size calculated based on the primary outcome? This needs to be specified.

Author Response:

Thank you for this valuable comment. We have revised the paragraph to clearly describe how the sample size was calculated. We specified the statistical test used (repeated-measures ANOVA), the key parameters (expected group difference, standard deviation, alpha, power), and the software (G*Power 3.1). Additionally, we cited the source used to define the expected difference and variability (Stern et al. [7]). The revised version improves clarity and methodological transparency.

 

9. I would suggest aligning the descriptions of the assessment tests. The Senior Fitness Test is described quite briefly, while the handgrip test is more detailed. I recommend describing the other tests in equal detail. Additionally, please specify the number of trials conducted for each test.

Author Response:

Thank you for this important observation. We have revised the manuscript to ensure that the descriptions of all functional fitness assessments are consistent in length and detail. We now provide more comprehensive descriptions for each component of the Senior Fitness Test (SFT), similar to the detail previously provided for the handgrip strength test. Furthermore, we specified the number of trials conducted for each test and clarified the criteria for selecting the final score (e.g., best of two attempts, total repetitions, distance, etc.). These revisions improve methodological transparency and reproducibility.

 

10. On line 158, "physical capacities" should be replaced with "physical fitness components."

Author Response:

Thank you for the suggestion. We have replaced the term “physical capacities” with “physical fitness components” on line 158 to ensure terminology consistency and alignment with the scientific literature in the field.

 

 

11. I suggest the authors explain how the activity was individually adapted and personalized, even though the activities were done in a group (on lines 215-217).

Author Response:

Thank you for the valuable comment. We have added a detailed explanation to clarify how the group-based HIIT intervention was individually adapted to participants’ functional levels and monitored using the Borg RPE scale. This addition helps reinforce the feasibility and safety of the protocol. (Please see lines XXX–XXX of the revised manuscript.)

 

12. How did the authors evaluate adherence to the project? Was a minimum participation frequency established for inclusion in the study? This should be clarified.

Author response:

Thank you for this observation. We have now clarified in the manuscript how adherence to the HIIT protocol was monitored. A minimum attendance threshold of 70% was established for inclusion in the final analysis. Adherence was tracked through attendance records at each session, and participants who failed to meet this threshold were excluded from the final analysis.

 

13. I would suggest describing and including RTE in the statistical analysis as well (RTE is only mentioned for the first time on line 279).

Author response:

Thank you for the valuable suggestion. We have now added a description of the Relative Treatment Effect (RTE) to the Statistical Analysis section to improve clarity and consistency. RTE was used as a nonparametric effect size measure in the Brunner–Langer model to quantify treatment group differences over time.

 

14. The objectives stated on lines 345-347 are slightly different from those in the introduction. In general, I would suggest making the innovative elements of this work explicit in the introduction compared to existing scientific studies (for example, focusing on the medium- to long-term effects of HIIT on physical efficiency components).

Author response:

Thank you for your valuable observation. We revised the introduction to explicitly highlight the innovative aspects of the study, particularly its medium- to long-term duration (65 weeks), real-world applicability, and use of non-machine-based HIIT in older adults. Additionally, we ensured consistency between the introduction and the discussion by clearly restating the study’s primary objective at the beginning of the discussion section. These adjustments enhance the coherence and clarity of the manuscript, emphasizing the originality and contribution of our research.

 

15. Furthermore, the HIIT protocol involves a significant increase in heart rate. Was this aspect taken into consideration by the authors? If so, how was heart rate monitored during the activities? This topic needs to be clarified.

Author response:

We thank the reviewer for this valuable comment. Although heart rate monitoring was not performed with electronic devices, exercise intensity was continuously controlled using the Borg Rating of Perceived Exertion (6–20). This scale was applied during each session to ensure that participants reached the appropriate intensity during high-intensity bouts and recovered adequately in between. A clarification regarding this has now been added to the Intervention section.

 

 

16. The conclusions are quite modest. As mentioned earlier, I suggest presenting the study's most original results concisely.

Author response:

Thank you for the suggestion. We revised the conclusion section to highlight the most original contributions of this study—particularly the long-term effects of HIIT on multiple domains of functional fitness in older adults, and the feasibility of implementing this intervention in real-world settings without the need for specialized equipment. These elements are now emphasized more clearly and concisely in the final paragraph of the Discussion and in the Conclusion section.

Reviewer 3 Report

Comments and Suggestions for Authors

Dear Authors,  It was with great interest that I received the scientific article “Effects of High-Intensity Interval Training on Functional Fitness in Older Adults A Randomized Controlled” for review by the scientific journal. I would like to note that the submitted article is related to my academic interests, which further convinced me to undertake the review. Therefore, please find below my suggestions and comments regarding the submitted scientific article:

1. In the keywords, replace the words ‘older adults’ with ‘adults’.
2. Line 46 please add citation/s
3. Line 72 - Apesar da eficácia potencial do HIIT, ainda há lacunas na literatura quanto aos seus it is not in English, please correct it.
4. Lack of citation in the following paragraph - Despite its promising potential, gaps remain in the literature regarding the effects of HIIT 73 on functional fitness in older adults—particularly outcomes directly related to independ- 74 ence in activities of daily living, such as upper and lower limb strength, mobility, flexibil- 75 ity, and aerobic endurance. Investigating the impact of this approach on functional pa- 76 rameters that support autonomy is, therefore, a priority given the current scenario of ac- 77 celerated population aging.
5. Subsection 2.1. Samples should be shortened – I understand that this subsection should contain information about the study group (age, gender). Please shorten this part of the scientific article.
6. Methodologically, authors should use gender-based classification in scientific work.
7. Please change the word women on female and men on male.
8. In table number one, add an explanation of all abbreviations used below the table and correct High Intensity Interval Trainin to High Intensity Interval Training.
9. In your academic paper, please elaborate on the practical conclusions drawn from the research results obtained, and in the conclusions section, please add information about future research.
10. Please correct the following citations in the section of References: 1, 4, 6 (this publication is from 1985 – please find some new one), 19, 20, 32.

Author Response

1. In the keywords, replace the words ‘older adults’ with ‘adults’.

Author response:

Thank you for your suggestion. We have replaced the keyword “older adults” with “adults” as requested.

 

2. Line 46 please add citation/s

Author response:

Thank you for your observation. We have added the appropriate citation(s) on line 46 to support the statement.

 

3. Line 72 - Apesar da eficácia potencial do HIIT, ainda há lacunas na literatura quanto aos seus it is not in English, please correct it.

Author response:

Thank you for pointing that out. The sentence was mistakenly written in Portuguese. We have corrected it to English in the revised version.

 

4. Lack of citation in the following paragraph - Despite its promising potential, gaps remain in the literature regarding the effects of HIIT 73 on functional fitness in older adults—particularly outcomes directly related to independ- 74 ence in activities of daily living, such as upper and lower limb strength, mobility, flexibil- 75 ity, and aerobic endurance. Investigating the impact of this approach on functional pa- 76 rameters that support autonomy is, therefore, a priority given the current scenario of ac- 77 celerated population aging.

Author response:  

Thank you for the observation. We have now added appropriate references to support the claims regarding the relevance of HIIT for improving functional fitness and autonomy in older adults, as well as the importance of addressing this topic given the global aging scenario.

 

 

5. Subsection 2.1. Samples should be shortened – I understand that this subsection should contain information about the study group (age, gender). Please shorten this part of the scientific article.

Author response:  

Thank you for your suggestion. In the revised version, we have shortened subsection 2.1 (Sample) to include only essential demographic characteristics of the study participants. Information regarding inclusion/exclusion criteria, recruitment, randomization, and sample size calculation has been relocated to appropriate new subsections to improve clarity and structure.

 

6. Methodologically, authors should use gender-based classification in scientific work.
7. Please change the word women on female and men on male.

Author response:  

Thank you for the observation. We have revised the manuscript to replace “women” and “men” with the terms “female” and “male” when referring to biological characteristics, in accordance with methodological standards for gender-based classification in scientific research.

 

8. In table number one, add an explanation of all abbreviations used below the table and correct High Intensity Interval Trainin to High Intensity Interval Training.

Author response:  

Thank you for your careful review. We have corrected the typo in “High Intensity Interval Trainin” to “High Intensity Interval Training” in Table 1. Additionally, all abbreviations used in the table (e.g., HIIT, BMI, SD, CI) have been explained in a note below the table for clarity and completeness.

 

9. In your academic paper, please elaborate on the practical conclusions drawn from the research results obtained, and in the conclusions section, please add information about future research.

Author response:

Thank you for the suggestion. We have expanded the conclusions section to include practical implications derived from our findings and added recommendations for future research directions.

 

10. Please correct the following citations in the section of References: 1, 4, 6 (this publication is from 1985 – please find some new one), 19, 20, 32.

Author response:

Thank you for this observation. We carefully reviewed the citations.

Reviewer 4 Report

Comments and Suggestions for Authors

The originality of the text was 90.05%.
The study was conducted in Portugal, at the Polytechnic Institute of Bragança and other institutions, including the Federal University of Viçosa in Brazil and the Polytechnic Institute of Guarda.
The article has high research interest, as it touches on a topical issue related to the increase in life expectancy and the need to maintain the health of older people. The results can be useful for both the scientific community and practitioners in the field of health.
This study has high scientific significance, as it aims to study the effect of high-intensity interval training (HIIT) on the functional physical fitness of older people. In the context of an aging population, maintaining functional independence and quality of life becomes critical. The results of the study can contribute to the development of effective physical activity programs for older people, which is important for public health.
The experimental part of the study is well-founded. The use of a randomized controlled design and standardized tests to assess functional physical fitness confirms the reliability of the data obtained.
The study makes a significant contribution to the literature on HIIT and its impact on functional fitness in older adults. It fills a gap in knowledge on how HIIT can improve physical activity and quality of life in this age group.
The presentation of the data in the study is high-quality. The results are presented in tables and graphs, which makes the information easy to understand.

The authors have done a great job by conducting a long-term study with clearly defined methods and protocols. Their contribution to the study of HIIT and its impact on older adults is valuable for further research in this area. The study is well organized, the methods are described in sufficient detail, and the results are presented clearly.

However, the following shortcomings should be noted:
1. The work does not have a clearly formulated hypothesis, which should be presented at the end of the Introduction section.

2. To assess the reliability of the data obtained, I recommend using simple parametric tests, such as Student's t-test, there is no need to use "exotic" methods in a simple determination of reliability.
3. Figure 2 is unclear, it is necessary to add explanations in the text on how to correctly interpret these diagrams?
4. I suggest removing the part “A Randomized Controlled” from the title of the article.
5. A logical question arises: can elderly people be given high-intensity interval training for functional training? This is a very risky undertaking that may cause an ambiguous reaction from the scientific sports community. I recommend revising the approach to solving the research goal.

Conclusion.
I recommend the article for publication after revision in terms of clarifying the hypothesis, improving the presentation of data and more clearly substantiating the statistical methods. It is recommended to make changes and resubmit the article for review.

Author Response

1. The work does not have a clearly formulated hypothesis, which should be presented at the end of the Introduction section.

Author response:

Thank you for the insightful suggestion. In the revised version of the manuscript, we have included a clearly formulated hypothesis at the end of the Introduction section, as follows:

“We hypothesized that participants undergoing the HIIT intervention would demonstrate significantly greater improvements in functional fitness components—including strength, flexibility, endurance, and mobility—compared to the control group.”

 

2. To assess the reliability of the data obtained, I recommend using simple parametric tests, such as Student’s t-test. There is no need to use “exotic” methods in a simple determination of reliability.

Author response:

We sincerely thank the reviewer for this suggestion. We fully understand and appreciate the importance of using established and parsimonious statistical methods whenever possible. However, the decision to apply the Brunner–Langer nonparametric ANOVA was based on the distributional properties of our dataset and the longitudinal design of the study.

In our preliminary analyses, several outcome variables violated the assumptions of normality and homogeneity of variances, even after standard transformation attempts. Given the repeated-measures nature of the data, with interaction effects (group × time), we sought a statistical model that could account for these characteristics without compromising the validity of the results.

The Brunner–Langer approach is a well-validated and widely recognized nonparametric method for longitudinal data analysis. It is particularly suitable for clinical and exercise science studies involving older adults, where variability and deviation from normality are common. Furthermore, this method allows for the interpretation of both main and interaction effects across time and groups, offering a robust alternative to parametric approaches under violated assumptions.

We hope this clarifies the rationale behind our choice, and we are, of course, open to discussing additional adjustments should the editorial team deem it appropriate.

 

3. Figure 2 is unclear, it is necessary to add explanations in the text on how to correctly interpret these diagrams.

Author response:

Thank you for this valuable observation. We have now added a brief explanation in the Results section to help readers interpret the visual elements presented in Figure 2. These include violin plots overlaid with boxplots, individual data points, and significance markers. The updated manuscript clarifies that the violin shape represents the data distribution, the boxplot indicates median and interquartile ranges, and the asterisks denote statistically significant differences between time points or groups, based on post hoc analyses.

 

4. I suggest removing the part “A Randomized Controlled” from the title of the article.

Author response:

Thank you for your suggestion. We agree that the phrase “A Randomized Controlled Trial” may be redundant, as the methodological design is already clearly described in the abstract and methods section. Accordingly, we have revised the title to:

“Effects of High-Intensity Interval Training on Functional Fitness in Older Adults”

We believe this version maintains clarity while improving the conciseness and impact of the title.

 

5. A logical question arises: can elderly people be given high-intensity interval training for functional training? This is a very risky undertaking that may cause an ambiguous reaction from the scientific sports community. I recommend revising the approach to solving the research goal.

Author response:

We appreciate your thoughtful concern regarding the applicability of high-intensity interval training (HIIT) in older adults. We fully acknowledge that traditional HIIT protocols can pose risks if not properly adapted. However, the present study employed a carefully designed, personalized HIIT protocol based on functional movements, without the use of resistance machines or maximal exertion. Training sessions were closely supervised by certified physiotherapists, and intensity was individually tailored using the Borg RPE scale, maintaining effort levels between 13 and 17 during high-intensity bouts — consistent with previously validated protocols [7–9].

 

Furthermore, existing literature supports the safety and effectiveness of HIIT in older populations when properly supervised and adapted, especially in improving cardiorespiratory fitness, muscular strength, and physical function [7–11]. Our study contributes to this field by evaluating the medium- to long-term effects of such an intervention under real-world conditions.

Therefore, we respectfully maintain the current methodological approach and objectives, while emphasizing throughout the manuscript that participant safety, clinical feasibility, and individualized adaptation were foundational principles of the intervention.

Reviewer 5 Report

Comments and Suggestions for Authors

Dear Authors,

I have had the opportunity to review your manuscript titled: “Effects of High-Intensity Interval Training on Functional Fitness in Older Adults: A Randomised Controlled” and commend you on the comprehensive approach and the relevance of your research within the field of exercise interventions for older adults. The study is well-conceived, and your findings contribute meaningful insights. However, I would like to offer several detailed suggestions to enhance the overall clarity, readability, coherence, and scholarly rigour of your report.

 

1. Structural Organisation with Clear Headings

The manuscript would benefit from the implementation of clearly defined section headings and subheadings. For example:

1. Section 2.1 Sample: it would benefit from implementing subheadings such as sample recruitment, inclusion and exclusion criteria, and sample size calculation.
2. Section 2.2.3 High Intensity Interval Training Programme: lines 218 to 220 describe the control group, which is confusing to read if it is under section 2.2.3.
3. It would be easier for the readers to follow if Section 2.2.2 and Section 2.2.3 Pre-test and post-test evaluation (lines 225 to 231) can be grouped closer together. Additionally, I presume there is a numbering error with the subsection, since there are two sections of 2.2.3.

While the current draft contains all of this information, having it subdivided can improve the overall readability of your good work. This structural refinement can facilitate smoother navigation of the content, guiding the reader through the methodological details, results, and discussion in a logical progression.

2. Enhanced Detailing of Methodological Approaches

While the statistical methods employed are appropriate, providing a more comprehensive explanation of the rationale behind selecting specific analytic techniques, such as the nonparametric Brunner-Langer ANOVA, would bolster the transparency and reproducibility of your work. Clarifying how these choices address the data characteristics and research questions would be advantageous. Additionally, please include the date the study was conducted in Section 2. Section 2.2.1, unfortunately, I cannot find any description of the measurement of body composition. Please consider either renaming the section or providing additional information on body compositions in both the Methods and the Results sections.

3. Use of Visual Aids to Summarise Key Findings

The inclusion of summarising tables, figures, or diagrams can significantly aid readers in comprehending complex data and results. Visual representations serve as practical tools for highlighting central trends, effect sizes, and significant outcomes, thereby enriching the manuscript’s communicative clarity. I would suggest organising the existing Results in tables or graphs, instead of the current paragraphs, as it both convolutes and lacks clarity. Additionally, information from lines 135 to 139, as well as the CONSORT flow diagram from Figure 1, should be reported under the Results section instead of Methods. Furthermore, much information, such as the effect size of the various comparisons, is only mentioned under the Discussion. This information should be clearly listed in the tables or graphs. It is not sufficient to report the F- or p-values under Results. Also, please increase the size of the plots in Figure 2. If the plots can only be viewed with a 300% zoom-in, this is not right. Rather importantly, can we have additional information on the gender distribution between the intervention and control group, rather than only reported as an overall figure? I also wonder if there were any sub-gender analyses performed, or if the authors can provide a reason for doing so (or not).

4. Clarity and Concise Writing Style

While it helps to write in refined sentence structures to avoid overly complex or lengthy statements, it is also essential to use concise language. The current manuscript is difficult to read due to its numerous, too-short paragraphs, some of which contain only a single sentence. Please consider reorganising the paragraphs and/or sections of the manuscript to enhance the overall clarity and readability. Adopting a more concise and precise writing style enhances accessibility, making the content more engaging and intelligible to a broad academic audience.

5. Broader Contextualisation

Where appropriate, expanding upon the contextualisation of your findings within the broader body of literature can underscore their significance and impact. This approach provides readers with a nuanced understanding of your research contribution.

Minor comments:

1. Minor Language and Formatting Improvements

Attention to minor language adjustments and adherence to consistent formatting conventions will elevate the overall presentation quality. For example,

1. Line 39, please refrain from using “elderly”. It can be replaced with “older adult” instead.
2. Line 72, I believe this should not be in the current version of the manuscript.
3. Line 282, I would like to seek clarification of whether the current version “with the HIIT group outperforming the HIIT group in the two-minute step test” is correctly written.

In summary, I believe addressing the above points will significantly improve the manuscript's clarity, rigour, and readability. Your work presents valuable insights; refining its presentation will ensure these insights are communicated as effectively as possible.

Thank you for the opportunity to review your research. I look forward to seeing the revised version.

 

Comments for author File: Comments.pdf

Author Response

1. Structural Organisation with Clear Headings

The manuscript would benefit from the implementation of clearly defined section headings and subheadings. For example:

1. Section 2.1 Sample: it would benefit from implementing subheadings such as sample recruitment, inclusion and exclusion criteria, and sample size calculation.
2. Section 2.2.3 High Intensity Interval Training Programme: lines 218 to 220 describe the control group, which is confusing to read if it is under section 2.2.3.
3. It would be easier for the readers to follow if Section 2.2.2 and Section 2.2.3 Pre-test and post-test evaluation (lines 225 to 231) can be grouped closer together. Additionally, I presume there is a numbering error with the subsection, since there are two sections of 2.2.3.

While the current draft contains all of this information, having it subdivided can improve the overall readability of your good work. This structural refinement can facilitate smoother navigation of the content, guiding the reader through the methodological details, results, and discussion in a logical progression.

Author response:

We appreciate the reviewer’s thoughtful suggestion regarding the structural organization of the manuscript. To enhance readability and improve the logical flow of the methodology section, we have reorganized Section 2 by implementing clear subheadings. Specifically, in Section 2.1 (“Sample”), we have added subheadings to distinguish sample recruitment, inclusion and exclusion criteria, and sample size calculation.

Furthermore, we corrected the numbering error in Sections 2.2.2 and 2.2.3 and ensured that the description of the control group is placed in its own clearly titled subsection (2.2.4 Control Group). We also rearranged the sequence of Sections 2.2.2 and 2.2.3 to present pre- and post-test evaluations in closer proximity and in the appropriate order.

 

2. Enhanced Detailing of Methodological Approaches

While the statistical methods employed are appropriate, providing a more comprehensive explanation of the rationale behind selecting specific analytic techniques, such as the nonparametric Brunner-Langer ANOVA, would bolster the transparency and reproducibility of your work. Clarifying how these choices address the data characteristics and research questions would be advantageous. Additionally, please include the date the study was conducted in Section 2. Section 2.2.1, unfortunately, I cannot find any description of the measurement of body composition. Please consider either renaming the section or providing additional information on body compositions in both the Methods and the Results sections.

Author response:

Thank you for your valuable suggestions. We have carefully addressed all points:

1. A more comprehensive explanation has been added to justify the use of the Brunner–Langer nonparametric ANOVA model, highlighting its robustness for repeated measures in non-normally distributed data and its suitability for heterogeneous older adult samples. This addition strengthens the methodological transparency and reproducibility of our findings.
2. The date range for data collection and intervention (January 2022 to May 2023) has now been included in Section 2.1 to enhance the clarity of the study timeline.
3. The title of Section 2.2.1 has been revised to “Anthropometry” to accurately reflect the content. Since no specific measures of body composition (e.g., fat mass, lean mass) were assessed, the term was removed to avoid confusion.

 

3. Use of Visual Aids to Summarise Key Findings

The inclusion of summarising tables, figures, or diagrams can significantly aid readers in comprehending complex data and results. Visual representations serve as practical tools for highlighting central trends, effect sizes, and significant outcomes, thereby enriching the manuscript’s communicative clarity. I would suggest organising the existing Results in tables or graphs, instead of the current paragraphs, as it both convolutes and lacks clarity. Additionally, information from lines 135 to 139, as well as the CONSORT flow diagram from Figure 1, should be reported under the Results section instead of Methods. Furthermore, much information, such as the effect size of the various comparisons, is only mentioned under the Discussion. This information should be clearly listed in the tables or graphs. It is not sufficient to report the F- or p-values under Results. Also, please increase the size of the plots in Figure 2. If the plots can only be viewed with a 300% zoom-in, this is not right. Rather importantly, can we have additional information on the gender distribution between the intervention and control group, rather than only reported as an overall figure? I also wonder if there were any sub-gender analyses performed, or if the authors can provide a reason for doing so (or not).

Author response:

Thank you for your thoughtful and constructive feedback. In accordance with your recommendation, the CONSORT flow diagram (Figure 1) has been relocated to the beginning of the Results section, and the Methods section was revised accordingly to enhance structural clarity and logical progression.

We fully agree with the importance of reporting effect sizes alongside p-values to support a more meaningful interpretation of the findings. Therefore, we have included the Relative Treatment Effect (RTE) values in Table 2, corresponding to the results of the nonparametric Brunner–Langer ANOVA. The RTE offers a robust, distribution-free effect size measure particularly suitable for repeated measures data with non-normal distributions, as observed in our older adult population.

Regarding Figure 2, we appreciate the reviewer’s comments about the compact presentation. While we acknowledge that the single-panel layout may appear dense, our intent was to present all functional fitness outcomes cohesively to allow easier visual comparison across time points and between groups. We have ensured that all elements, including labels and symbols, are legible and appropriately scaled for both digital and print viewing. That said, we remain open to reformatting the figure (e.g., splitting into two separate panels) if preferred by the Editorial Team.

Finally, concerning the gender distribution and subgroup analyses, we clarify that gender balance was considered at baseline, with 40 females and 39 males evenly randomized between groups. However, subgroup analyses by gender were not performed, as our primary goal was to assess the effects of HIIT in a general older adult population. Further stratification could have reduced statistical power given the sample size. Nevertheless, we acknowledge the relevance of this suggestion, and we agree that future research should explore potential gender-specific responses to HIIT interventions.

Once again, we thank the reviewer for these valuable insights, which contributed to strengthening the clarity, transparency, and scientific rigor of our manuscript.

 

4. Clarity and Concise Writing Style

While it helps to write in refined sentence structures to avoid overly complex or lengthy statements, it is also essential to use concise language. The current manuscript is difficult to read due to its numerous, too-short paragraphs, some of which contain only a single sentence. Please consider reorganising the paragraphs and/or sections of the manuscript to enhance the overall clarity and readability. Adopting a more concise and precise writing style enhances accessibility, making the content more engaging and intelligible to a broad academic audience.

Author response:

Thank you for your insightful recommendation regarding the clarity and organization of the manuscript. We acknowledge that overly fragmented or excessively brief paragraphs may hinder the fluidity of reading and reduce overall coherence.

In response, we carefully revised the manuscript to consolidate related ideas into more cohesive and structured paragraphs, reducing unnecessary breaks and improving logical progression. Additionally, we made efforts to enhance the conciseness and precision of the language, avoiding redundancy and simplifying overly complex constructions, while preserving scientific rigor.

We believe these adjustments have significantly improved the readability, flow, and accessibility of the text for a broader academic audience, and we sincerely appreciate the reviewer’s guidance in helping us achieve this.

 

5. Broader Contextualisation

Where appropriate, expanding upon the contextualisation of your findings within the broader body of literature can underscore their significance and impact. This approach provides readers with a nuanced understanding of your research contribution.

Author response:

We appreciate the reviewer’s insightful comment regarding the broader contextualisation of our findings. In response to earlier reviewers’ suggestions, we have already revised the manuscript to enhance the interpretability and relevance of our results within the existing literature.

In the Discussion section, the main findings are now consistently compared with previous studies on HIIT and other exercise interventions targeting functional fitness in older adults. These comparisons help position our study within the current evidence base, highlight consistencies and divergences, and underscore the practical implications of our long-term intervention.

We believe these refinements improve the scientific contextualisation of our findings, and we thank the reviewer for reinforcing the importance of this aspect.

 

6. Minor Language and Formatting Improvements

Attention to minor language adjustments and adherence to consistent formatting conventions will elevate the overall presentation quality. For example,

Line 39, please refrain from using “elderly”. It can be replaced with “older adult” instead.

Line 72, I believe this should not be in the current version of the manuscript.

Line 282, I would like to seek clarification of whether the current version “with the HIIT group outperforming the HIIT group in the two-minute step test” is correctly written.

Author response:

We thank the reviewer for these helpful observations and suggestions aimed at improving the language and consistency of the manuscript.

• In line 39, the term “elderly” has been replaced with “older adults”, in alignment with current age-inclusive language standards in gerontology and public health literature.
• In line 72, the sentence or phrase referenced has been removed, as it was mistakenly retained from an earlier draft version.
• In line 282, we have corrected the sentence, which previously read: “with the HIIT group outperforming the HIIT group in the two-minute step test”. This was a typographical error, and it now correctly states: “with the HIIT group outperforming the control group in the two-minute step test.”

We sincerely appreciate the reviewer’s attention to detail, which has helped us improve the clarity and quality of the manuscript.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

I would congratulate authors for the enormous effort in answering all comments and suggestions. 

The proposed revisions are adeguate and useful to enhance the quality of the manuscript, the significance of the contents and a better understanding of findings. 

I recommend the publication of the manuscript in the present form. 

 

Best compliments

Author Response

We sincerely thank the Reviewer for the kind words and for recognizing our efforts in revising the manuscript. We are very grateful for the positive feedback and for the recommendation for publication.

Reviewer 5 Report

Comments and Suggestions for Authors

Dear Authors, 

Thank you very much for the revision. Most of the manuscript reads a lot clearer with the revision. However, several aspects could still benefit from better structuring of the manuscript to enhance the overall readability. These are as follows: 

1. Line 52, a typo error.
2. Table 2: I would like to seek clarification on the data points from Table 2. Are they the descriptive statistics from M1? If not, which timepoints would that be? Further revision is needed on this table. 
3. Previously, I suggested collating the results, specifically referring to the information from lines 328 to 394. Personally, I found the current presentation format convoluted and lacking a clear presentation of the findings of your good study. The additional RTE, while it is absolutely good to have them now, further complicate the readability of the overall results. 
4. Additionally, the small violin plots, though I appreciate the reasons you have provided for keeping them small and will defer to the editorial's decision should the manuscript be accepted, I mean to say it is very tiring and tedious after having navigated the long convoluted descriptions from lines 328 to 394, and then having to squint the eyes to try interpreting the violin plots. I apologise for the straightforwardness; this seriously turned off my interest in continuing to read the manuscript, which should not be the case, considering the good effort the team has put into this wonderful RCT! 
5. Line 463: There is a mention of Cohen's d; however, I don't recall that Cohen's d is used to establish the effect size from your methods > statistical analysis. 
6. Lines 467: Please clarify what is HIICT.

Please consider my suggestions. 

Regards, 

Author Response

We sincerely thank the Reviewer for the careful re-reading and for the constructive suggestions aimed at improving structure and readability. We addressed each point as follows:

1. Line 52 — typo

   Corrected as suggested.

2. Table 2 — clarification of timepoint and revision

   Table 2 now clearly reports post-intervention (M3) descriptive statistics. We revised the caption and added a clarifying sentence immediately before the table in the Results section to prevent any ambiguity.

 

• Text before the table (added): “Table 2 presents the descriptive statistics (mean, median, SD, 95% CI, and RTE) for both groups at the post-intervention (M3) timepoint.”

• Caption (revised): “Table 2. Descriptive statistics of functional fitness variables in the HIIT and Control groups at the post-intervention (M3) timepoint.”

 

3. Results (lines 328–394) — structure, readability, and RTE density

   We restructured this subsection to improve flow and reduce cognitive load:

• We now begin each outcome/domain with a one-to-two-sentence summary of the main finding.

• The narrative retains only essential statistics (ATS and p values), while full model outputs and additional contrasts were moved to Supplementary Material.

• RTE values are integrated in Table 2 and not repeated exhaustively in the text; they are mentioned only when they meaningfully aid interpretation.

  These changes make the section more linear and readable, so the reader does not reach the figure already fatigued.

4. Figure readability (small violin plots)

   We thank the Reviewer for this observation. Following the suggestion, we attempted to increase the overall dimensions of Figure 2, enlarging the panels, axis labels, and legends to improve readability. We believe this adjustment makes the figure clearer and easier to interpret, while preserving the distributional detail of the violin plots.

5. Line 463 — Cohen’s d

   We acknowledge the Reviewer’s observation. This was included by mistake, and we have now removed Cohen’s d completely from the manuscript to maintain consistency with the nonparametric statistical approach adopted.

6. Line 467 — “HIICT”

   We corrected this term and clarified that it referred to High-Intensity Interval Circuit Training (HIICT) in the cited study. In our manuscript, the terminology is now consistently presented as HIIT when referring to our intervention.

 

We appreciate the Reviewer’s guidance. Collectively, these revisions improve structure, clarity, and visual readability of the Results, helping the reader navigate the narrative smoothly without eye strain before reaching the figure, while preserving the scientific rigor of our analyses.

 

Best regards.