Posterior Pelvic Tilt During the Squat: A Biomechanical Perspective and Possible Solution with Short-Term Exercise Intervention

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript reports the topic of posterior pelvic tilt during squatting and examines the fast effects of a short exercise intervention on PPT range of motion. The study contains detailed physiotherapy assessments, 3D kinematic motion study, and a clear explanation of the exercise protocol. While the study is carefully designed and conducted, several methodological and interpretive limitations should be addressed before publication.

1.Why was no true control/placebo group used that received no involvement? Since both groups completed the same exercise protocol, how can you separate the real effect of the involvement from natural adaptation or repetition of the movement?

2.Please explain whether the sample size was sufficient to detect small differences in PPT ROM between the experimental and control groups.
3. Were the control and experimental groups fully standardized based on the initial pelvic position and sex distribution?
4. How might the results vary if the participants were beginners or had pre-existing musculoskeletal conditions, such as low back pain?

5.Participants were divided into experimental and control groups based only on the timing of PPT onset. Do you think this grouping introduce bias instead of reflecting true intervention effects?

6.The intervention continued only 15–20 minutes. Given that the intervention was short-term and low-intensity, is it realistic to expect immediate changes in PPT ROM?

7.Have you thought of a follow-up measurement like 24 hours or 1 week later to figure out if the effect is temporary or lasting?

8. Do you think that the use of X-ray or dynamic MRI offer more reliable information on pelvic alignment and anatomical predispositions?
9. Do you think these results could be widespread to non-athlete populations or individuals new to strength training?

10.How the author defines a “physiologically normal” against “excessive” PPT range?

11.Do you think it would be worthwhile to extend the study to a longer intervention period to measure training-induced adaptations?

Author Response

Comments 1: Why was no true control/placebo group used that received no involvement? Since both groups completed the same exercise protocol, how can you separate the real effect of the involvement from natural adaptation or repetition of the movement?

Response 1: There was no control group due to the small number of participants. It is true that if there is no true control group, this affects the internal validity of the sample under investigation to a certain extent.

Comments 2: Please explain whether the sample size was sufficient to detect small differences in PPT ROM between the experimental and control groups.

Response 2:  No, it would have required approximately 130 participants - we added this fact to the discussion in our study.

Comments 3: Were the control and experimental groups fully standardized based on the initial pelvic position and sex distribution?

Response 3: No, the division was only based on the occurrence of PPT during bodyweight squats.

Comments 4: How might the results vary if the participants were beginners or had pre-existing musculoskeletal conditions, such as low back pain?

Response 4: We mention this in the discussion. We know that low back pain completely changes the way movement is performed. Theoretically, the group with back pain could show different results than those we achieved.

Comments 5: Participants were divided into experimental and control groups based only on the timing of PPT onset. Do you think this grouping introduce bias instead of reflecting true intervention effects?

Response 5: Yes, you can influence the internal validity of the sample of subjects involved in the study.

Comments 6: The intervention continued only 15–20 minutes. Given that the intervention was short-term and low-intensity, is it realistic to expect immediate changes in PPT ROM?

Response 6: According to some studies (low-intensity exercise intervetion), yes, but it usually takes a longer period of time (4 to 8 weeks).

Comments 7: Have you thought of a follow-up measurement like 24 hours or 1 week later to figure out if the effect is temporary or lasting?

Response 7:  A follow-up measurement was planned in the original design, but it did not ultimately take place. We would definitely recommend implementing this in a future study.

Comments 8: Do you think that the use of X-ray or dynamic MRI offer more reliable information on pelvic alignment and anatomical predispositions?

Response 8: Definitely, but such examinations are costly in terms of money and time, and also expose participants to radiation.

Comments 9: Do you think these results could be widespread to non-athlete populations or individuals new to strength training?

Response 9: Probably not, because beginners or those who do not exercise regularly could benefit more from exercise intervention, as they have not yet established their own stereotypical squat technique.

Comments 10: How the author defines a “physiologically normal” against “excessive” PPT range?

Response 10: PPT is usually classified as dangerous/excessive if it occurs before reaching a parallel squat; if it occurs later, it is often considered a normal phenomenon.

Comments 11: Do you think it would be worthwhile to extend the study to a longer intervention period to measure training-induced adaptations?

Response 11: Absolutely, and we also included this recommendation in the discussion and conclusions of the study.

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript addresses the phenomenon of posterior pelvic tilt (PPT) during squatting and evaluates whether a short exercise intervention can immediately reduce pelvic range of motion in the sagittal plane. The topic is relevant for sports science, physiotherapy, and injury prevention, and it fits within the journal’s Applied Biosciences and Bioengineering scope.

However, despite the solid motivation and an extensive theoretical background, the current version of the paper does not meet the scientific rigor, methodological precision, and writing standards required for publication. The experimental design has critical flaws in participant classification, data analysis, and interpretation of results. Moreover, the writing, while generally understandable, is overly verbose, redundant, and lacks structural clarity in several sections.

The study seems to have been carefully conducted, but the experimental intervention is too weak to support meaningful biomechanical conclusions, and the statistical approach though complex is insufficiently justified and sometimes misapplied. The discussion is disproportionately long, reiterating limitations instead of synthesizing key findings or linking them to practical implications.

Overall, the paper would require major revision before it could be reconsidered.

Abstract (p.1, lines 14–42)

• The abstract is excessively long and descriptive. It should emphasize problem, method, main findings, implications more concisely.
• Line 19–23: The phrase “divided according to the incidence of posterior pelvic tilt…” is confusing; clarify whether allocation was random or based on pre-existing conditions.
• Line 32–38: Reporting p-values without corresponding effect sizes or confidence intervals limits interpretability.
• The conclusions should explicitly state the practical relevance of the null finding, e.g., “A single 20-min corrective session does not acutely alter pelvic kinematics.”

Introduction (pp.2–5, lines 44–201)

• The introduction demonstrates thorough literature knowledge but lacks focus. It reads like an extensive review rather than a concise rationale leading to testable hypotheses.
• Line 54–63: The explanation of “butt wink” should be condensed and referenced only to key biomechanical sources.
• Lines 101–116: The paragraph on hip and ankle ROM duplicates later discussion, streamline.
• The final paragraph (lines 187–201) introduces hypotheses but needs clearer operational definitions (e.g., how “statistically significant effect” or “increased anterior tilt” were quantified).
• Recommendation: Condense this section to ~2 pages focusing on (1) prevalence and risk of PPT; (2) gaps in evidence; (3) specific aim and hypotheses.

Methods (pp.5–10, lines 202–382)

• Study Design: (lines 203–211). The study is described as a “controlled experiment,” but it lacks randomization, blinding, or control of confounders. It is essentially a quasi-experimental pre–post design. Clarify this explicitly.
• Sample: (lines 212–223). The inclusion criteria are acceptable, but the grouping method (based on PPT occurrence) introduces circular reasoning: grouping participants by the outcome measure compromises internal validity.
• Physiotherapy Examination: (lines 224–281). This section is overly detailed, including procedures irrelevant to the main outcome. Much of this should be summarized or moved to supplementary materials.
• Kinematic Motion Analysis: (lines 282–319). Equipment and procedures are well described; however:
• Line 295: marker count and positioning are appropriate, but the rationale for using the CODA pelvis model should be justified with validation references.
• The sampling frequency (100 Hz) is sufficient, yet filtering methods are not mentioned, were raw data smoothed?
• No mention of inter-trial reliability, calibration accuracy, or error quantification (typical error, ICC, SEM).
• Exercise Intervention: (lines 320–326). The intervention is minimal (six low-intensity exercises for 15–20 min). It is unrealistic to expect measurable biomechanical adaptations after such a brief exposure; therefore, the hypothesis appears conceptually weak.
• Statistical Analysis: (lines 333–369).
• The use of both REML and rANOVA is inconsistent; justify why both were needed.
• Effect sizes (η², Cohen’s d) should accompany p-values.
• No power analysis is provided; this omission undermines the credibility of null findings.
• The manuscript states “residual normality analysis was performed,” but provides no results. Include diagnostics in supplementary material.

Results (pp.10–13, lines 383–459)

• The results are presented clearly but with insufficient statistical depth.
• Line 429–435: The statement “borderline of statistical significance (p = 0.06)” is inappropriate  p = 0.06 is non-significant; avoid implying otherwise.
• Figures 5–7 lack quantitative scales and error bars; they resemble qualitative plots rather than analytical figures.
• The text often repeats information already visible in figures; condense to highlight main outcomes.
• Consider adding confidence intervals and individual data dispersion (boxplots) to support transparency.

Discussion (pp.13–17, lines 460–659)

• The discussion is overly long, repetitive, and largely devoted to listing limitations rather than interpreting findings.
• The first paragraph (lines 460–469) should explicitly restate the null results and their biomechanical meaning.
• Lines 471–487: Good acknowledgment of measurement errors, but this section reads as an internal audit rather than a scientific discussion.
• Lines 520–573: The arguments about motor learning and fatigue are speculative; no data support them. Trim or substantiate with citations.
• Lines 574–607: The critique of sample size and grouping is accurate but belongs in a “Limitations” subsection.
• The discussion lacks integration with prior literature quantifying PPT angles during squatting (e.g., Sinclair et al., 2015; Schoenfeld, 2010).
• No practical application or theoretical model is offered. What does the absence of change imply for rehabilitation practice?
• The language occasionally becomes conversational (“we dare say,” “we would consider…”). Replace with neutral, scientific phrasing.

Conclusions (pp.17–18, lines 660–669)

• The conclusion correctly reflects the results but is too tentative and self-referential (“we would be very pleased if someone else…”). Remove personal tone.
• It should emphasize the study’s contribution (e.g., providing baseline data on pelvic motion) and the main limitation (short intervention).
• Suggest future research directions concisely, focusing on longer, higher-intensity interventions and improved methodology.

References and Formatting

• Some references (e.g., [7], [12]) are websites or blog posts not acceptable for a scientific paper. Replace with peer-reviewed sources.
• Reference style generally follows MDPI format but check italics and DOI inclusion consistency.
• Ensure all in-text citations correspond to listed references (spot-check: [75] and [94] missing or mismatched).

Figures and Tables

• Figures 1–4 are acceptable, but Figures 5–7 require clearer legends and statistical annotations.
• Table 1 could be simplified: merge the “Description” and “Goal” columns for brevity.
• Resolution of figures appears low; ensure publication-ready quality.

Author Response

Thank you for your comprehensive review. We will respond to each point individually below:

Abstract – edited, shortened, and reworked

Introduction – shortened by approximately one page

Methods - better formulation of the type of research, added some information on 3D kinematic analysis, shortened the section on physiotherapy, added information on statistical data processing

Results - edited graphs, added effect size

Discussion - shortened and more focused on the results found

Conclusions - edited and better formulated

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

1. Overall assessment

The manuscript submitted for review addresses an important and topical issue in the field of strength training biomechanics, namely posterior pelvic tilt (PPT) during squats. The subject matter of the manuscript indicates that it could be highly applicable in the context of both sports training and rehabilitation. The work is carefully prepared, has a logical structure, and a rich theoretical background based on a solid literature base. However, the methodological part and the interpretation of the results require clarification, and some conclusions are overinterpreted in relation to the data obtained.

2. Strengths of the manuscript

A very broad and up-to-date review of the literature on the PPT phenomenon, anatomical and functional factors, and practical recommendations.

A high methodological level in the field of 3D kinematic measurements using the Qualisys system.

Transparent presentation of the limitations of the study and factors that may influence the results (including fatigue, standardization of squat depth, and participant experience).

Correct use of statistical analyses (REML, rANOVA) and control of individual effects (participant as a random effect).

3. Critical comments and recommendations

3.1. Methodology

Sample selection: 42 people is a moderate number, but the lack of power analysis makes it difficult to assess the reliability of negative results. Information on the required sample size that would allow for reliable conclusions should be provided, or it should be noted that the study is a pilot study.

Division into groups: The assignment criterion (time of onset of PPT) may cause heterogeneity in terms of pelvic position, experience, or mobility. It is worth considering stratification of the study group by gender and/or pelvic tilt angle. Conducting parallel analyses according to several division criteria may be interesting for a complete picture of the phenomenon.

Intervention: The duration (20 minutes) and low intensity of the exercise program do not allow us to realistically expect significant motor changes. This should be clearly stated in the title or abstract (e.g., “short-term intervention”). In the future, I would consider a greater load, especially in terms of the intensity of the subjects.

Lack of control over squat depth: Although the authors mention this in the limitations, it would be worth proposing more precise standardization in future studies (e.g., use of a box squat or photocell system).

3.2. Analysis and interpretation of results

The results did not show significant differences, but the authors suggest a “trend” towards a reduction in PPT. This wording should be toned down—in the absence of a statistical effect, such statements can be misleading.

There is too much speculation in the discussion (e.g., the influence of fatigue, motor learning) that has not been directly measured. I suggest shortening this section and limiting interpretations to the observed data.

There is a lack of information on the effect size, which makes it difficult to assess the practical significance of the results. This statistical method should be included in the statistical analysis of the data.

3.3. Style and presentation

The text is well written, but needs to be shortened in places, especially in the literature review and discussion section.

It would be useful to add a figure showing the average kinematic course of pelvic movement for both groups (before and after the intervention), which would facilitate interpretation.

The abstract should more clearly emphasize that the effect of the intervention was not significant and indicate potential directions for further research (e.g., longer interventions, greater intensity).

4. Reviewer's conclusions

The study is a valuable contribution to the analysis of the “butt wink” phenomenon, but the current experimental design and short intervention do not allow for causal conclusions to be drawn. After revisions (clarification of methodology, supplementation of statistical power, reduction of overinterpretation), the article may be accepted after major revisions (major revision).

5. Suggested directions for further research

Extend the intervention to at least 4–6 weeks with progressive loading.

Inclusion of EMG measurements of muscles stabilizing the torso and pelvis.

Analysis of the impact of different foot width settings and limitations in the hip and ankle joints.

Author Response

Thank you for your comprehensive review. We will respond to each point individually below:

Methodology - the title and abstract of the article have been revised, information has been added stating that this is a pilot study, and some information (squat depth) has been added to the discussion.

Analysis and interpretation of results + Style and presentation - The discussion and theory were shortened and focused more on the problem addressed in the research, the type of study was better formulated, and the effect size was added.

Suggested directions for further research - added to discussion and conclusion.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

I read the manuscript titled “Posterior Pelvic Tilt During the Squat: A Biomechanical Perspective and Possible Exercise Solution” with interest. This study addresses a relevant question in sports science and rehabilitation: whether a brief exercise intervention can improve posterior pelvic tilt (PPT) control during squatting in healthy individuals. The manuscript is well-structured, clearly written, and the experimental methods are appropriately described. The following are my minor comments:

While the methodology is sound overall, a few clarifications would improve transparency:

• Squat depth control: Squat depth was self-selected and not standardized, which introduces variability. Please clarify whether any measures (e.g., verbal guidance, visual cues) were taken to ensure consistency, and suggest how future studies might address this (e.g., using a box or depth markers).
• Pelvic angle definition: The manuscript defines the pelvic tilt angle based on ASIS–PSIS orientation relative to the vertical axis, but does not clearly state whether negative values indicate posterior tilt. Please clarify the direction of angle change and consider including a simple schematic.
• Marker accuracy: Since ASIS and PSIS markers are prone to soft tissue artifacts during movement, it would be appropriate to briefly acknowledge this limitation in the Methods or Discussion.

Author Response

Thank you for your review. We will respond to each point individually below:

Squat depth control - added to the discussion, including a possible solution

Pelvic angle definition - added to the methodology

Marker accuracy - information about STA added to methodology

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,
After carefully reviewing the revised version of your manuscript, I confirm that you have thoroughly addressed the reviewers’ comments and implemented all requested modifications appropriately. The revisions have notably enhanced the clarity, methodological rigor, and overall quality of the work. Therefore, I consider the manuscript suitable for publication in its current form.

Best regards