Effects of an 8-Week Abdominal Hypopressive Technique Program on Pelvic Floor Muscle Contractility: An Assessor-Blinded Randomized Controlled Trial

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This is a randomized controlled trial to evaluate an exercise on pelvic floor muscle. Here are some comments:

- The paper might have missed several important pieces of content because it did not comply with the CONSORT reporting guidelines. It is mandatory for the journal. 

- The introduction lacks context for a literature review, in particular different kinds of clinical (or non-clinical) trials of related training or rehabilitation techniques. Similarly, a discussion on the different maneuvers of these papers and how is are different/align with the maneuvers of the authors research. 

- In introduction, the authors already mentioned that the technique and the evaluation of the technique are not new. In such a sense, what is the contribution of the authors?

- In Methods, Line 106, there is no detail description on how to perform the AHT, and how "progressive" is "progressive"? The description of the protocol is insufficient. 

-In Methods, Line 136, please align the statisitical methods with its purpose and the objectives. 

- Comparisons of p-value because of multiple tests are missing. 

- Effect size (e.g., partial eta square) shall be included and analyzed.

- The caption of the Tables shall be self-explanatory and currently insufficient.

- The discussion lacks an in-depth explanation on how the proposed technique helps. In Line 192, the information is too rough.

- Line 225, "AHT can be considered a suitable and safe training". This conclusion is not supported by evidence. Similar problems appeared in Line 239, the conclusion and the abstract. Please focus on the effectiveness of the training in improving muscle strength and how it might implicate the treatment of urinary incontinence. 

- Limitations shall include factors related to clinical variations, methodological errors, and sampling factors.  

Comments on the Quality of English Language

Minor grammatical mistakes

Author Response

RESPOND TO REVIEWER 1 FIRST ROUND

 

This is a randomized controlled trial to evaluate an exercise on pelvic floor muscle. Here are some comments:

- The paper might have missed several important pieces of content because it did not comply with the CONSORT reporting guidelines. It is mandatory for the journal. 

Thank you very much for noticing this issue. Although we consider it a very important topic, we do not fully understand which pieces are missed. We would be grateful if the reviewer could be more precise.

- The introduction lacks context for a literature review, in particular different kinds of clinical (or non-clinical) trials of related training or rehabilitation techniques. Similarly, a discussion on the different maneuvers of these papers and how is are different/align with the maneuvers of the authors research. 

We have added more information regarding rehabilitation techniques and maneuvers as follow:

However, the current literature on clinical and non-clinical trials using similar training or rehabilitation techniques remains scattered and lacks a systematic review of their effectiveness. Previous studies have examined alternative methods, such as Kegel exercises, biofeedback training, and functional electrical stimulation, in order to improve PFM functionality (6,7). These approaches have been compared to AHT, but there is still no consensus regarding their relative effectiveness, particularly in terms of muscle contractility and endurance.

[…] To provide a more comprehensive understanding of the field, it is important to discuss different maneuvers used in related studies and how they compare them to those implemented in our research. For instance, studies such as Resende et al. (5) have examined the combination of AHT with other interventions, whereas Vieira et al. (12) have assessed the differences between training modalities, including active and passive muscle stimulation. These studies highlight the need to consider multiple training parameters, such as duration, frequency, and intensity, to optimize results. Our study aims to contribute to this growing body of evidence by focusing specifically on PFM strength improvements resulting from a systematic AHT program.

- In introduction, the authors already mentioned that the technique and the evaluation of the technique are not new. In such a sense, what is the contribution of the authors?

Regarding this concern, the aim of the study is to bring more information about how an exercise program using AHT affects PFM strength specifically. We consider, in the best of our knowledge, that there are few studies in the literature aiming on that topic.

- In Methods, Line 106, there is no detail description on how to perform the AHT, and how "progressive" is "progressive"? The description of the protocol is insufficient. 

We agree that the description was poor. We have added information to the protocol description as follows:

During the intervention weeks, the complexity and intensity of the exercises increased progressively, starting with static postures lying on the back, followed by static postures in a seated and standing position, and concluding with dynamic postures that required coordinating breathing with movement.

-In Methods, Line 136, please align the statisitical methods with its purpose and the objectives. 

We thank the reviewer for the comment. Nevertheless, we consider the required information is in the test. Notwithstanding, a sentence was not fully clear and has been modified.

Between-group differences were analyzed using independent t-tests, while paired t-tests assessed within-group changes were performed.

- Comparisons of p-value because of multiple tests are missing. 

The reviewer is correct. This is a secondary analysis of the initial thesis. We have lowered the level of significance with the Bonferroni correction:

Statistical significance was initially set at p<0.05, and then to 0.015 to correct for multiple hypotheses.

- Effect size (e.g., partial eta square) shall be included and analyzed.

Our apologies. It has been included now:

The trial's minimum sample size was determined using Stata (version 10.0, StataCorp, College Station, Texas, USA). The calculation was based on a 20% increase in the normal pelvic tone (225g/cm2), the trial's primary endpoint. Power was set at 80% (β = 0.20), and the alpha level at 0.05. The estimated required sample size was n=16 participants per group.

- The caption of the Tables shall be self-explanatory and currently insufficient.

The captions have been completed

- The discussion lacks an in-depth explanation on how the proposed technique helps. In Line 192, the information is too rough.

We thank the reviewer for the comment. Nevertheless, we consider the utility of the technique has been demonstrated, at least in the present study, regarding improvements in PFM strength. We respectfully do not understand what is the reviewer´s concern. The same happens with the comment about line 192. We do not understand the meaning of rough in this contest. We apologized for the lack of understanding of the reviewer´s needs.

- Line 225, "AHT can be considered a suitable and safe training". This conclusion is not supported by evidence. Similar problems appeared in Line 239, the conclusion and the abstract. Please focus on the effectiveness of the training in improving muscle strength and how it might implicate the treatment of urinary incontinence. 

Sadly, we have to disagree with the reviewer, as the complete sentence is as follows: “In conclusion, AHT can be considered a suitable and safe training option for improving PFM strength in adult women”, where the part of improving PFM strength in adult women we consider crucial. According to the results here presented, an intervention with AHT improves PFM strength. Therefore, we consider  that the conclusion is supported by the present study results and so, for the evidence. Regarding the second part of the comment, we consider we did focus on the effect on strength.

- Limitations shall include factors related to clinical variations, methodological errors, and sampling factors.  

We have added a paragraph highlighting a possible problem during the measurements.

Furthermore, the feedback provided by the Phenix device during measurements may facilitate learning how to contract and localize the PFM, which, in itself, could improve MVC independently of the intervention

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

 

This study investigates the impact of the Abdominal Hypopressive Technique (AHT) on pelvic floor muscle (PFM) strength, addressing an important and relevant topic. However, several major issues need to be addressed, as they may affect the generalizability of the conclusions and the overall reliability of the study. Below, detailed comments are provided for each section.

 

#1. Clarity of Objectives (Abstract): The study aims to evaluate the effects of an 8-week AHT program on PFM strength in adult women with no prior experience with AHT. However, the rationale behind selecting only inexperienced participants is not clearly explained.

 

#2. Choice of Outcome s(Abstract): The definitions of "load absorption" and "muscle efficiency" are unclear. Further explanation is needed on how AHT mechanistically enhances these parameters.

 

#3. Interpretation of Statistical Results (Abstract): The abstract presents p-values, but does not report effect sizes (e.g., Cohen’s d) or confidence intervals, making it difficult to assess the clinical relevance of the findings.

 

#4. Generalization of Conclusions (Abstract): The study concludes that AHT is a safe, non-invasive, and effective intervention. However, without a comparative group, these conclusions should be presented with greater caution.

 

#5. Insufficient Background Information (Introduction): The introduction states that research on AHT’s impact on PFM function is limited but does not specify which aspects remain unexplored.

 

#6. Lack of Explanation on Neurological Mechanisms (Introduction): The explanation of how AHT affects PFM activation through posture and diaphragmatic breathing needs to be expanded with supporting references.

 

#7. Justification of Study Hypothesis (Introduction): The hypothesis that "AHT improves PFM strength" is stated, but the rationale for focusing on contraction strength is unclear. Further elaboration on how strength improvements relate to functional benefits (e.g., urinary incontinence reduction) is needed.

 

#8. Inconsistency in Sample Size Calculation and Allocation (Materials and Methods): The study states that a priori power analysis determined that 16 participants per group were needed. However, 21 participants per group were ultimately assigned, which is methodologically incorrect. The sample size calculation and its application should be reconsidered.

 

#9. Sample Size Justification (Materials and Methods): While power analysis was performed, the assumption that a 20% difference would be clinically meaningful is not justified. More details are needed on the estimated standard deviation and threshold for clinical relevance.

 

#10. Standardization of Intervention (Materials and Methods): The AHT program lacks detailed descriptions of exercises, postures, and intensity levels, raising concerns about reproducibility.

 

#11. Reliability of Measurements (Materials and Methods): The study uses the Phenix Biofeedback Kit to measure PFM strength, but no information is provided on its measurement error or prior validation. Additionally, it is unclear whether assessors were blinded.

 

#12. Transparency in Statistical Analysis (Results): p-values alone are insufficient; effect sizes and confidence intervals should be provided to clarify clinical significance.

 

#13. Interpretation of Control Group Data (Results): PFM strength in the control group decreased post-intervention, yet no explanation is offered. Possible factors such as measurement error, learning effects, or participant compliance should be considered.

 

#14. Unclear Explanation of Secondary Outcomes (Results): The definitions and relevance of "muscle efficiency (ME)" and "closure capacity (CC)" are not adequately explained in the results.

 

#15. Clarification of Dropouts: The presence or absence of participant dropouts should be explicitly stated. If there were dropouts, their reasons and potential impact on results should be discussed.

 

#16. Causal Inference Issues (Discussion): The study attributes PFM strength improvement to AHT without considering placebo effects or psychological influences. A more cautious interpretation is necessary.

 

#17. Lack of Comparison with Other Interventions (Discussion): The effectiveness of AHT is not compared with conventional PFM training methods (e.g., Kegel exercises), making it difficult to determine its relative efficacy.

 

#18. Limitations in Clinical Application (Discussion): While the study suggests AHT is useful for urinary incontinence management, this study did not directly measure incontinence symptoms. The claim should be revised accordingly.

 

#19. Overgeneralization of Findings (Conclusion): The study lacks long-term data to support claims that AHT is "safe, non-invasive, and effective." The conclusion should be more restrained.

 

#20. Practical Recommendations Needed (Conclusion): More guidance should be provided on which patient populations might benefit most from AHT.

 

#21. Future Research Directions (Conclusion): The need for long-term follow-up and comparative studies with other training methods should be emphasized.

Author Response

Dear Reviewer,

Please see the author's reply in the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The study assess the effects of Abdominal Hypopressive Technigue program on pelvic floor muscle contractility.I have the following comments:

-In the Abstract part,you have utilised "MCV1",without defining the term.Please provide full name when first utilised in text.

-"load absorbtion"-what represent the numbers in brackets?Time in seconds,or what else?

-Major comment.You took in the study 42 females.These females had urinary incontinence or not?I understand that they have no urinary incontinence.

-row 107-112 Please describe briefly AHF  and provide a citation to a study where this technique is described in details.

-row 115 "Phenix Biofeedback Kit" Please provede a link to an address where the device is described(for example producer site).

-row 97-100 Where was performed the study?

-Major comment.Why didn't you performed the study on patients with urinary incontinence?In the Conclusions part you stated that AHT program  have "implication for improving UI symptoms",but your study is about women without UI.

-Major comment.I didn't found on ClinicalTrials.gov the study after the NCT number.Apparently is not a correct number.

-

Author Response

Dear Reviewer,

Please see the author's reply in the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors had improved the manuscript based on the queries. Here are some follow-up comments.

1. In abstract, critical information on conclusion shall be: the intervention significantly improved the "outcome" and the level of improvement is significantly greater than the control group (if this is the case). 
2. Section 2.4 Outcome measures shall be after 2.5 Procedure.
3. The data analysis part is still not clear. Specifically, it shall be mentioned that the within-group test is to evaluate the before and after treatment effect on which outcome measures. For the between-group test, it is unclear whether the comparison is on the post-treatment outcome adjusted by baseline, or the change of pre-post outcome. It is important to get these correct. 
4. The limitation part is yet insufficient. Based on your criteria, is it a convenient sampling or random sampling? the study might not apply for females and also age, or ethnicity beyond the samples and these confounders shall be discussed (which is also required by the CONSORT guidelines). 
5. The authors disagreed with my comment that the conclusion is not conservative enough. If this is the case, please illustrate which piece of your experimental results prove that your intervention is "safe" and "suitable" directly. Did the authors conduct a safety test or a formal usability test on the participants? These are all just insights and are not part of the study results. The authors might consider put more weights on their key results and illustrate its direct implications derived by the results in a logical way. Instead, putting more conservative tone (e.g., could be) on indirect insights or guesses. 

Author Response

RESPOND TO REVIWER 1 SECCOND ROUND

1. In abstract, critical information on conclusion shall be: the intervention significantly improved the "outcome" and the level of improvement is significantly greater than the control group (if this is the case). 

We have added “comparing with the CG.” To the conclusion in the abstract as recomended

1. Section 2.4 Outcome measures shall be after 2.5 Procedure.

The order has been changed in the manuscript as suggested.

1. The data analysis part is still not clear. Specifically, it shall be mentioned that the within-group test is to evaluate the before and after treatment effect on which outcome measures. For the between-group test, it is unclear whether the comparison is on the post-treatment outcome adjusted by baseline, or the change of pre-post outcome. It is important to get these correct. 

The reviewer is correct. We hope it is clearer now witj the following paragraph:

Between-group differences in the change pre-post in load absorption, MVC1, and MVC2 were analyzed using independent t-tests, while paired t-tests assessed within-group changes were performed.

1. The limitation part is yet insufficient. Based on your criteria, is it a convenient sampling or random sampling? the study might not apply for females and also age, or ethnicity beyond the samples and these confounders shall be discussed (which is also required by the CONSORT guidelines). 

"We appreciate the reviewer’s observation regarding the limitations of our study. We confirm that the sampling method used was a non-probabilistic convenience sampling, as participants were recruited based on accessibility and willingness to participate. Consequently, this limits the generalizability of our findings beyond the specific characteristics of the sample. We acknowledge that the results may not apply to populations with different age ranges, ethnic backgrounds, or health conditions not represented in our cohort. Additionally, potential confounding variables such as hormonal status, physical activity level outside the intervention, or individual neuromuscular differences were not controlled. In compliance with CONSORT guidelines, we have now revised the limitations section to address these concerns explicitly.". Therefore, the following paragraph has been added:

This study has several limitations. First, the sampling method was non-probabilistic and based on convenience and voluntary participation, which limits the generalizability of the findings to broader populations. The results may not apply to women from different age groups, ethnic backgrounds, or with health conditions not represented in our sample. Furthermore, potential confounding variables—such as hormonal status, baseline physical activity, or individual neuromuscular characteristics—were not controlled and could have influenced the outcomes. Future research should aim to include more diverse and randomly selected samples to enhance external validity and better understand the applicability of AHT in various populations. On the other hand,

1. The authors disagreed with my comment that the conclusion is not conservative enough. If this is the case, please illustrate which piece of your experimental results prove that your intervention is "safe" and "suitable" directly. Did the authors conduct a safety test or a formal usability test on the participants? These are all just insights and are not part of the study results. The authors might consider put more weights on their key results and illustrate its direct implications derived by the results in a logical way. Instead, putting more conservative tone (e.g., could be) on indirect insights or guesses.

We appreciate the reviewer’s concern and we have now revised both the discussion and the conclusion to adopt a more conservative tone. In particular, we clarified that although no adverse events or difficulties were reported during the intervention, no formal safety or usability assessment was conducted. We now refer to these observations cautiously and emphasize the need for future research to validate the safety and broader applicability of AHT

Although no formal safety or usability assessment was conducted, it is worth noting that none of the participants reported any adverse effects, discomfort, or difficulties in following the AHT sessions throughout the intervention period. Moreover, the technique requires no equipment and is based on low-intensity breathing and postural exercises, which are generally well-tolerated. These observations suggest that AHT could be considered a potentially safe and accessible option for future implementation in pelvic floor rehabilitation programs.

This study shows that an eight-week AHT program significantly improves PFM strength in healthy, inactive women. While these findings support AHT as a promising training method for pelvic floor muscle enhancement, future research is warranted to confirm its clinical relevance and to formally evaluate its safety and applicability in broader populations.

In conclusion, AHT could be considered an alternative and effective training tool option for improving PFM strength in adult women without contraindications to perform this technique.

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

Thank you for your thorough revisions. While many of the concerns have been addressed, there are still several critical issues that need further clarification and improvement. Please find below additional comments that should be addressed to enhance the robustness and clarity of your study.

 

#4. Details of the Intervention Protocol

Your response states that the detailed intervention protocol has been published elsewhere. However, relying solely on external references is not appropriate. Readers of this manuscript should be able to reproduce the intervention without needing to access an external publication.

Recommendation:

• Provide a summary of the key elements of the AHT intervention in the Methods section.
• Include a brief description of the exercises, postures, duration, and intensity.
• If necessary, supplementary material can be used to present more details while avoiding duplication of previously published content.

 

#6. Mention of Urinary Incontinence in the Conclusion

You have stated that urinary incontinence (UI) data were collected in a previous publication but were not included in this study. However, your manuscript still discusses UI in the conclusion. If UI outcomes were not measured in this study, they should not be included in the conclusion.

Recommendation:

• Remove any claims related to the effectiveness of AHT on UI from the conclusion.
• If you wish to discuss UI, clearly state that it was not assessed in this study and provide a reference to your previous publication.

 

#8. Sample Size Calculation and Participant Allocation

You have justified increasing the sample size to account for possible dropouts. However, simply increasing the number of participants without adjusting the original sample size calculation lacks statistical validity.

Recommendation:

• Conduct and report a sensitivity analysis to evaluate the impact of recruiting additional participants on the study’s statistical power.
• Discuss how the increase in sample size may have influenced the study’s findings and potential biases.
• If the power calculation remains valid despite the increase, provide justification with supporting statistical evidence.

 

#9. Clinical Relevance of a 20% Improvement

Your response states that a 20% improvement threshold was chosen based on prior literature. However, there is no clear justification that this value represents a clinically meaningful change.

Recommendation:

• Provide specific references that define 20% as a clinically meaningful threshold in the context of pelvic floor muscle function.
• If no consensus exists, acknowledge this limitation and justify why this threshold was selected for this study.
• Include a discussion of how this threshold compares to established benchmarks in similar research.

 

#11. Validation and Reliability of Measurement Devices

You have added references to support the use of the Phenix Biofeedback Kit. However, the extent to which these references validate the device’s accuracy and reliability remains unclear. Additionally, measurement error data should be explicitly provided.

Recommendation:

• Clearly explain how the cited studies validate the accuracy and reliability of the Phenix Biofeedback Kit for measuring PFM strength.
• If available, provide data on measurement error, test-retest reliability, and inter/intra-rater reliability.
• Discuss how measurement error could influence the study’s findings and how potential bias was minimized.

Author Response

RESPOND FOR THE REVIEWER 2 SECOND ROUND

Thank you for your thorough revisions. While many of the concerns have been addressed, there are still several critical issues that need further clarification and improvement. Please find below additional comments that should be addressed to enhance the robustness and clarity of your study.

 

#4. Details of the Intervention Protocol

Your response states that the detailed intervention protocol has been published elsewhere. However, relying solely on external references is not appropriate. Readers of this manuscript should be able to reproduce the intervention without needing to access an external publication.

Recommendation:

• Provide a summary of the key elements of the AHT intervention in the Methods section.
• Include a brief description of the exercises, postures, duration, and intensity.
• If necessary, supplementary material can be used to present more details while avoiding duplication of previously published content.

A new document with the protocol has been included as supplementary documentation.

 

#6. Mention of Urinary Incontinence in the Conclusion

You have stated that urinary incontinence (UI) data were collected in a previous publication but were not included in this study. However, your manuscript still discusses UI in the conclusion. If UI outcomes were not measured in this study, they should not be included in the conclusion.

Recommendation:

• Remove any claims related to the effectiveness of AHT on UI from the conclusion.
• If you wish to discuss UI, clearly state that it was not assessed in this study and provide a reference to your previous publication.

We thank the reviewer for the appreciation and we agree that, as we do not give any data related to UI we cannot conclude about that issue. Nevertheless, in the reviewed text, it was already stated that no data of UI were provided, but as scientific evidence might suggest that improving PFM strength can be related to better continence, we simple suggest that AHT, in the way it increases strength, can have implications in UI

This study provides compelling evidence that a two-month AHT program significantly enhances PFM strength. Although UI data are not presented in this case, the observed improvements in pelvic floor muscle strength are consistent with previous research suggesting that enhanced PFM function may contribute to better UI outcomes. Therefore, our findings may have potential implications for UI prevention and management through strength-oriented pelvic floor interventions. AHT is a safe, non-invasive intervention that can serve as a valuable tool in pelvic floor rehabilitation. Continued research is essential to optimize its implementation and to compare its outcomes with alternative interventions.

 

#8. Sample Size Calculation and Participant Allocation

You have justified increasing the sample size to account for possible dropouts. However, simply increasing the number of participants without adjusting the original sample size calculation lacks statistical validity.

Recommendation:

• Conduct and report a sensitivity analysis to evaluate the impact of recruiting additional participants on the study’s statistical power.
• Discuss how the increase in sample size may have influenced the study’s findings and potential biases.
• If the power calculation remains valid despite the increase, provide justification with supporting statistical evidence.

The increase in sample size was done to account for problems with measurement or lost to follow-up. Also, it was based on the primary endpoint, which was not the objective of this analysis. We have evaluated the impact on power for the endpoints shown in this secondary analysis with the actual values encountered and using the observed combined SD. The following analysis demonstrate so.

Estimated power for a two-sample means test for Load Absorption

t test assuming sd1 = sd2 = sd

H0: m2 = m1  versus  Ha: m2 != m1

 

Study parameters:

 

        alpha =    0.0500

            N =        42

  N per group =        21

        delta =   22.7000

           m1 =   -3.5000

           m2 =   19.2000

           sd =   27.0592

 

Estimated power:

 

        power =    0.7557

 

Estimated power for a two-sample means test for MVC1 (gr/cm2)

t test assuming sd1 = sd2 = sd

H0: m2 = m1  versus  Ha: m2 != m1

 

Study parameters:

 

        alpha =    0.0500

            N =        42

  N per group =        21

        delta =  289.1000

           m1 =  -71.0000

           m2 =  218.1000

           sd =  282.9275

 

Estimated power:

 

        power =    0.8981

 

Estimated power for a two-sample means test for MVC2 (gr/cm2)

t test assuming sd1 = sd2 = sd

H0: m2 = m1  versus  Ha: m2 != m1

 

Study parameters:

 

        alpha =    0.0500

            N =        42

  N per group =        21

        delta =  189.3900

           m1 =   -6.8400

           m2 =  182.5500

           sd =  250.2701

 

Estimated power:

 

        power =    0.6675

 

As expected, the increase in sample size did not affect relevantly the statistical power to detect differences between groups in the endpoints in this analysis. Furthermore, the power was decreased in some comparisons thus the probability of not detecting an effect when the effect was truly present was increased. We have added this explanatory sentence in the manuscript :

“The estimated required sample size was n=16 participants per group; this was then increased by 30% to account for non-response and lost to follow-up.”

#9. Clinical Relevance of a 20% Improvement

Your response states that a 20% improvement threshold was chosen based on prior literature. However, there is no clear justification that this value represents a clinically meaningful change.

Recommendation:

• Provide specific references that define 20% as a clinically meaningful threshold in the context of pelvic floor muscle function.
• If no consensus exists, acknowledge this limitation and justify why this threshold was selected for this study.
• Include a discussion of how this threshold compares to established benchmarks in similar research.

We agree with the reviewer that a 20% difference may not be clinically relevant. However, when we designed the study several years ago, we did not have sufficient evidence to base the sample size calculations on an expected effect. Furthermore, a 20% difference was an acceptable improvement for most physical therapies 10 years ago. We have included this as a limitation in our study:

“Also, we based our sample size estimations on detecting a 20% difference, which may not be considered clinically relevant; however, when we started our study, evidence was not sufficient to base sample size on an even larger effect.”

#11. Validation and Reliability of Measurement Devices

You have added references to support the use of the Phenix Biofeedback Kit. However, the extent to which these references validate the device’s accuracy and reliability remains unclear. Additionally, measurement error data should be explicitly provided.

Recommendation:

• Clearly explain how the cited studies validate the accuracy and reliability of the Phenix Biofeedback Kit for measuring PFM strength.
• If available, provide data on measurement error, test-retest reliability, and inter/intra-rater reliability.
• Discuss how measurement error could influence the study’s findings and how potential bias was minimized.

We appreciate the reviewer’s comments regarding the accuracy and reliability of the Phenix Biofeedback Kit. While the manufacturer does not provide formal data on measurement error or test-retest reliability, the device has been used in clinical and research contexts to assess PFM function. For instance, studies such as Resende et al. (2012) and Soriano et al. (2020) have used the Phenix system to measure MVC of the PFM and reported it as a valid and responsive tool in similar populations. However, no published validation studies have provided specific error margins, test-retest reliability coefficients, or intra/inter-rater reliability for the model used in our study. We acknowledge this as a limitation and have added this point to the discussion section.

To minimize potential measurement bias, all assessments were performed by the same experienced evaluator using standardized instructions and a consistent procedure across all sessions. Furthermore, participants received training prior to baseline testing to ensure familiarity with the contraction technique, which may help reduce intra-subject variability. While we cannot completely exclude measurement error, we believe that its impact is likely minimal and does not compromise the internal validity of the results.

A paragraph in the limitation section has been included:

Finally, another limitation of this study is the absence of specific data on the measurement error or test-retest reliability of the Phenix Biofeedback Kit model used. Although the device is commonly used in clinical practice and has been applied in previous studies to assess PFM strength, further validation studies are needed to determine its accuracy, reliability, and sensitivity to change.

Reviewer 3 Report

Comments and Suggestions for Authors

The authors responded well to all my comments,and completed the article,raising very much the quality of the presentation.

Author Response

The reviewer 3 did not included comments in the second round

Round 3

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

 

Thank you for your continued efforts in revising the manuscript. I appreciate the improvements you have made, particularly regarding the inclusion of a supplementary document for the intervention protocol, clarification of the sample size power analysis, and the acknowledgment of limitations related to measurement tools and effect size assumptions. However, several important concerns remain insufficiently addressed. Please see the detailed comments below:

 

1. Intervention Protocol (#4)

You have added a supplementary document describing the AHT protocol, which is helpful. However, the main text of the manuscript still lacks a sufficient description of the intervention. It is essential that readers can understand and replicate your method without relying solely on supplementary materials or external references.

Recommendation:

Please include a concise summary of the key components of the AHT protocol in the Methods section, such as the type and duration of exercises, frequency per week, postures used, and intensity progression (if any).

 

2. Mention of Urinary Incontinence in the Conclusion (#6)

Although you have acknowledged that urinary incontinence (UI) was not assessed in this study, the conclusion still implies potential effectiveness of AHT for UI. This is speculative and may mislead readers.

Recommendation:

All references to UI should be removed from the conclusion unless the outcome was directly assessed in this study. If you wish to discuss it in the discussion section, it must be clearly framed as hypothetical and supported by citations from other studies—not by the current data.

 

3. Sample Size and Power Justification (#8)

You provided post-hoc power calculations to demonstrate that the increased sample size did not negatively impact the study’s statistical power. While helpful, this does not fully address the methodological inconsistency between the original sample size calculation and the actual participant allocation.

Recommendation:

Please provide a clearer justification for the decision to increase the sample size beyond the calculated requirement, and discuss how this may have influenced the study’s statistical validity, particularly with respect to potential biases.

 

4. Clinical Significance of 20% Improvement (#9)

Thank you for your transparency in explaining the historical rationale behind the 20% threshold. Acknowledging this as a limitation is appropriate and appreciated. No further revisions are needed here.

 

5. Measurement Device Validity (#11)

You have cited relevant studies and acknowledged the lack of formal measurement error or reliability data for the Phenix Biofeedback Kit. However, your manuscript still lacks sufficient detail to fully convince readers of the instrument’s validity.

Recommendation:

If available, please provide any additional data (even approximate) regarding test-retest reliability, intra-rater variability, or known sources of measurement error. If such data do not exist, further emphasize this limitation in your discussion.

Author Response

RESPONDS TO REVIEWER 2 THIRD ROUND

 

Dear Reviewer:

Below you can find the responses to the comments. We thank you in advance for all the help in improving the manuscript.

 

1. Intervention Protocol (#4)

You have added a supplementary document describing the AHT protocol, which is helpful. However, the main text of the manuscript still lacks a sufficient description of the intervention. It is essential that readers can understand and replicate your method without relying solely on supplementary materials or external references.

Recommendation:

Please include a concise summary of the key components of the AHT protocol in the Methods section, such as the type and duration of exercises, frequency per week, postures used, and intensity progression (if any).

Following the comments, the intervention section has been modified as follows:

The intervention program consisted of AHT sessions performed three times a week on alternative days, over 8 weeks (a total of 24 group sessions), each lasting 30 minutes. The program involved progressive AHT postures incorporating different arm positions, diaphragmatic breathing and postural adjustments (axial elongation, ribcage expansion). Each session began with postures in standing position, followed by kneeling positions, quadruped, sitting and lying positions. Once completed, the exercises were repeated in reverse order starting in supine position and finishing in standing position. For the study, all postures were repeated three times and apnoea was maintained an average of 30 seconds. The first week was lighter, just learning the exercises. The intervention focused on optimizing body alignment and diaphragmatic aspiration through vacuum techniques. During the intervention weeks, the complexity and intensity of the exercises increased progressively, starting with static postures lying on the back, followed by static postures in a seated and standing position, and concluding with dynamic postures that required coordinating breathing with movement. The time in apnea started at 15 seconds and was increasing progressively till 30 seconds. Table 1 shows the details of the training protocol. A complete explanation of the exercises performed can be found as supplementary file.

 

1. Mention of Urinary Incontinence in the Conclusion (#6)

Although you have acknowledged that urinary incontinence (UI) was not assessed in this study, the conclusion still implies potential effectiveness of AHT for UI. This is speculative and may mislead readers.

Recommendation:

All references to UI should be removed from the conclusion unless the outcome was directly assessed in this study. If you wish to discuss it in the discussion section, it must be clearly framed as hypothetical and supported by citations from other studies—not by the current data.

Following the reviewer´s indications, the conclusion has been modified as follows:

The observed improvements in pelvic floor muscle strength are consistent with previous research suggesting that enhanced PFM function may contribute to better continence outcomes. Therefore, our findings indirectly may have potential implications for preventing and managing pelvic floor disfunctions through strength-oriented pelvic floor interventions

 

1. Sample Size and Power Justification (#8)

You provided post-hoc power calculations to demonstrate that the increased sample size did not negatively impact the study’s statistical power. While helpful, this does not fully address the methodological inconsistency between the original sample size calculation and the actual participant allocation.

Recommendation:

Please provide a clearer justification for the decision to increase the sample size beyond the calculated requirement, and discuss how this may have influenced the study’s statistical validity, particularly with respect to potential biases.

We truly appreciate the observation and understand the concern. Initially, an a priori sample size calculation indicated that at least 16 participants per group (32 participants in total) were required to achieve 80% power with an alpha error of 0.05, to detect a clinically relevant difference of 20% in pelvic floor muscle tone and strength between groups, as indicated in the manuscript.

However, as is standard practice in clinical intervention trials, we proactively increased this initial sample size by approximately 30% (resulting in 42 participants, 21 per group) to account for potential dropouts, loss to follow-up, or protocol non-compliance (attrition). This approach follows widely accepted methodological recommendations to safeguard statistical validity by compensating for anticipated participant attrition (Detry & Lewis, 2016; Dumville et al., 2006).

Unexpectedly, our study experienced zero dropouts, resulting in the full recruited sample completing the trial. Consequently, we ended up with a slightly larger sample size than originally estimated. Importantly, this methodological decision to proactively increase the sample size did not introduce biases or negatively impact the statistical validity of our findings. Rather, it ensured robustness and improved the statistical power of our analysis, strengthening the internal and external validity of the study outcomes by minimizing risks associated with potentially insufficient statistical power (underpowered studies).

We firmly believe that this methodological practice not only aligns with best-practice guidelines but also enhances the reliability and interpretability of the findings reported.

References:

• Detry, M. A., & Lewis, R. J. (2016). The intention-to-treat principle: How to assess the true effect of choosing a medical treatment. JAMA, 315(1), 85-86.
• Dumville, J. C., Torgerson, D. J., & Hewitt, C. E. (2006). Reporting attrition in randomised controlled trials. BMJ, 332(7547), 969-971.

We do consider that the section in the manuscript provides sufficient information. The text stayed as follows:

An “a priori” sample size was calculated with an 80% power and an alpha error of 0.05 to detect a 20% minimum difference in PFM tone and strength between groups. The estimated required sample size was n=16 participants per group; this was then increased by 30% to account for non-response and lost to follow-up (total, n=32). 

1. Clinical Significance of 20% Improvement (#9)

Thank you for your transparency in explaining the historical rationale behind the 20% threshold. Acknowledging this as a limitation is appropriate and appreciated. No further revisions are needed here.

We thank you for the big help to improve the manuscript

 

1. Measurement Device Validity (#11)

You have cited relevant studies and acknowledged the lack of formal measurement error or reliability data for the Phenix Biofeedback Kit. However, your manuscript still lacks sufficient detail to fully convince readers of the instrument’s validity.

Recommendation:

If available, please provide any additional data (even approximate) regarding test-retest reliability, intra-rater variability, or known sources of measurement error. If such data do not exist, further emphasize this limitation in your discussion.

We thank the reviewer for his/her continued attention to the issue of measurement validity. As previously stated, the Phenix Biofeedback Kit has been widely used in both clinical practice and research; however, we acknowledge that formal data regarding its test-retest reliability and intra-rater variability are currently unavailable for the specific model used in our study. After contacting the manufacturer, we were only able to obtain technical specifications, such as a pressure measurement precision of ±1 mmHg. No formal validation studies providing standard error of measurement (SEM), ICC coefficients, or Bland–Altman analysis are available at this time.

Given this limitation, we have now revised the manuscript to more explicitly acknowledge the absence of reliability data for the device. In the revised Discussion section, we have added a statement as follows:

Another important limitation of this study is the absence of formal data on test-retest reliability or measurement error for the specific model of the Phenix Biofeedback Kit used. While this device is commonly employed in clinical and research settings to assess PFM strength, its psychometric properties have not been systematically established in scientific literature. Consequently, the potential impact of measurement variability cannot be fully ruled out, and future studies are encouraged to evaluate the reliability and validity of this instrument in controlled conditions.

Author Response File: Author Response.docx