Step-Level Characteristics of Pickup Acceleration Performance in Team-Sport Athletes

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors

This manuscript addresses a relevant and still underexplored topic in applied sprint biomechanics, namely pickup acceleration from submaximal rolling entries. The study has practical relevance for team sports and offers a potentially useful step-by-step analysis across two entry velocities. The manuscript is generally well structured, and the topic is of interest to both researchers and practitioners.

However, in its current form, the manuscript has important methodological and analytical limitations that weaken the strength of the conclusions. In particular, the grouping strategy, the statistical approach, the derivation and definition of key variables, and the interpretation of the findings require substantial revision. Overall, the study has merit, but major revision is required before it can be considered  publication,

The main concern is the circularity between group allocation and the main outcome variables. Participants were divided into “fast” and “slow” groups based on maximal acceleration, and then compared using variables closely derived from acceleration, especially step acceleration and estimated horizontal force. This makes the central conclusion partly tautological. The authors should either reanalyze the data using a more appropriate continuous approach or substantially soften the interpretation and frame the findings as associations rather than explanatory  mechanisms.

The statistical strategy is limited. The use of multiple independent t-tests across several variables, steps, and entry conditions increases the risk of type I error and does not take full advantage of the repeated structure of the data. A mixed-model or repeated-measures approach would be more appropriate. At minimum, the limitations of the current approach should be explicitly acknowledged.

Key variable definitions need clarification. The descriptions of step velocity and step horizontal force are currently ambiguous and, in places, difficult to reconcile with standard biomechanical definitions. The equations and units should be reported clearly and consistently so that the method is reproducible.

The step-identification procedure includes manual intervention by the researcher, but no reliability data are provided. Given that the analysis depends heavily on manual event selection and derived acceleration measures, the manuscript should report at least intra-rater reliability, and ideally inter-rater reliability as well.

The discussion at times overinterprets the findings. The authors infer technical and mechanical determinants, such as body orientation and force application strategy, that were not directly measured in this study. Because the instrument used estimates variables indirectly and has recognized limitations, the causal language should be reduced throughout the manuscript, including in the title and conclusion.

Some aspects of the experimental design require clearer reporting. It should be explicitly stated whether the fast/slow grouping was performed separately within each entry-velocity condition. The criteria used to determine whether participants successfully matched the prescribed entry velocity should also be described more  precisely.

The abstract is clear overall, but some wording is too strong given the design and should be made more cautious.

The methods section would benefit from clearer presentation of the data-processing workflow, ideally including the exact equations used for all derived  variables.

The discussion is informative but somewhat repetitive in places and could be  streamlined.

Table presentation should be checked carefully for formatting and possible numerical inconsistencies (Table 2 ("158.7 ± 0.78")).

The reference list requires stylistic standardization and careful proofreading.

The English is generally understandable, but the manuscript would benefit from moderate language editing for clarity and precision.

Kind regards,

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

The study addresses a relevant and underexplored aspect of sprint performance, particularly in the context of non-static starts typical of team sports. The step-level analytical approach represents a meaningful contribution, and the dataset appears sufficiently rich to support valuable insights.

At the same time, several aspects of the methodological design and interpretation require clarification and refinement in order to ensure the robustness and credibility of the findings. I outline these below together with concrete suggestions for improvement.

A central concern relates to the way participant groups are defined. The division into “fast” and “slow” groups is based on maximal acceleration (amax), which is subsequently used as a primary outcome variable. This creates a circular analytical structure that limits interpretability. To address this issue, I recommend one of the following solutions. First, if feasible, redefine the grouping variable using an independent performance metric, such as split time (e.g., 0–10 m), or maximal velocity (vmax). This would immediately remove the circularity. Alternatively, if regrouping is not possible, the manuscript should explicitly acknowledge this limitation and avoid presenting amax differences as confirmatory findings. In practical terms, this could be implemented by adding a sentence in the Methods and Discussion clarifying that group differences in amax are structurally embedded in the grouping procedure and should therefore be interpreted descriptively rather than inferentially.

A second important issue concerns the estimation of step horizontal force. SFh is currently calculated as a function of body weight and step acceleration, which represents a simplified proxy rather than a direct biomechanical measurement. While this approach is acceptable, the interpretation in several parts of the manuscript implies a stronger mechanical validity than is justified. I recommend explicitly reframing SFh as an estimated variable. This could be achieved by introducing a clarifying statement in the Methods (e.g., “SFh was estimated based on step acceleration and should be interpreted as a proxy measure rather than a direct ground reaction force component”). In addition, expressions suggesting direct causality (e.g., “clearly influences”) should be softened to associative language (e.g., “is associated with” or “may contribute to”). Expanding the limitations section to explicitly discuss the absence of force vector orientation and ground reaction force decomposition would further strengthen the manuscript.

The step identification procedure introduces another important methodological consideration. The use of manual adjustments in MATLAB, while understandable, introduces potential observer bias and affects reproducibility. To improve transparency, I recommend that the authors provide a more detailed description of the criteria used for manual corrections (e.g., thresholds, visual markers, decision rules). If possible, reporting intra-rater reliability (e.g., repeated analysis of a subset of trials) would significantly strengthen confidence in the data processing. If such analysis is not available, a concise acknowledgment in the limitations section would be sufficient but necessary.

From a statistical standpoint, the use of multiple independent t-tests across steps and variables raises the risk of inflated Type I error. A practical solution would be to apply a correction procedure such as Bonferroni or false discovery rate (FDR). If the authors prefer not to apply corrections, this decision should be explicitly justified, and the interpretation of marginal p-values (e.g., p ≈ 0.05–0.06) should be made more conservative. A short addition in the Statistical Analysis section acknowledging this issue would be appropriate.

Regarding the positioning of the study within the existing literature, some claims of novelty appear overstated. I recommend revising these statements using more cautious formulations, such as “to the authors’ knowledge” or “this study extends previous work by…”. This adjustment can be implemented with minimal changes but will improve the academic tone and credibility.

In terms of readability, the Results section would benefit from a reduction in abbreviation density. While the use of variables such as SFh, Sa, Sv, and SL is appropriate, their repeated and dense use may challenge the reader. A practical improvement would be to reintroduce full terms at the beginning of each subsection or selectively replace abbreviations with full expressions in key interpretative sentences.

The Discussion section is generally well-developed, but at several points it moves into speculative explanations regarding technical or biomechanical mechanisms (e.g., body positioning or strategy). These interpretations are valuable but should be clearly marked as hypotheses. This can be achieved by introducing phrases such as “it is possible that…” or “one potential explanation is…”, thereby distinguishing data-driven findings from interpretation.

Finally, the Conclusion would benefit from a clearer articulation of practical implications. At present, it summarizes the findings effectively but stops short of translating them into applied recommendations. I suggest adding one or two sentences explicitly addressing how these findings could inform training interventions, performance diagnostics, or coaching strategies (e.g., emphasizing horizontal force production in early pickup steps).

In summary, the manuscript has a solid conceptual foundation and addresses an important topic with a promising analytical approach. The suggested revisions primarily concern clarification, methodological transparency, and more cautious interpretation rather than fundamental redesign. Addressing these points would substantially enhance the scientific rigor and applied value of the work.

I hope these comments prove helpful in strengthening the manuscript.

Sincerely

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors,

The revised manuscript has improved and addressed several previous concerns, particularly by clarifying the grouping procedure, softening causal language, expanding the methods, and adding a Bonferroni correction. These changes strengthen the manuscript.

However, some scientific concerns remain. The main limitation is that participants are still grouped according to maximal acceleration and then compared using acceleration-related variables, especially step acceleration and estimated step horizontal force. Although the authors now acknowledge this and frame the results more cautiously, the manuscript should consistently present the findings as descriptive associations rather than true determinants.

The statistical interpretation should also be fully aligned with the Bonferroni-corrected alpha level (i.e. statistical interpretation should be made fully consistent with the revised analysis. The manuscript states that a Bonferroni-corrected alpha of 0.01 was adopted. Yet, some parts of the Results and Discussion still refer to findings with p 0.04 or p 0.05 in ways that may still suggest meaningful statistical differences. Even if the authors intend to discuss effect sizes and descriptive patterns, the distinction between statistically significant findings after correction and non-significant trends should be made much clearer throughout). In addition, the equations and definitions for derived variables, especially estimated SFh, Sa, and Sv, should be clarified further to ensure full reproducibility. The added reliability information is helpful, but it remains unclear whether it applies specifically to all step-level variables central to this study.

Overall, the manuscript is stronger than before and remains potentially publishable, but further revision is still needed to improve scientific framing, statistical consistency, and methodological precision.

Kind regards,

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

Thank you for the careful revisions made throughout the manuscript. Most previously raised concerns have now been addressed appropriately, and the manuscript has improved substantially in terms of methodological transparency and interpretative balance.

One remaining issue, however, requires minor revision to ensure full consistency between the statistical procedure and the interpretation of the findings.

Specifically, after introducing the Bonferroni correction in the Statistical Analysis section (adjusted α = 0.01), several results with p-values above this threshold are still described in a manner implying statistical significance. This creates a mismatch between the adopted statistical framework and the narrative interpretation.

Please revise the following sections accordingly:

1. Results – 1.5 m/s Entry Velocity (pp. 6–8; Table 1 interpretation)

Examples:

• “moderately longer step length (p = 0.04; 11.0%) was observed”
• “moderate to large increases (p < 0.05...)”

Suggested correction direction:
These findings should be reframed as the following:

• “non-significant tendencies,”
• “descriptive differences,”
• or “moderate effects not reaching the adjusted significance threshold.”

Reason for revision:
After applying the Bonferroni correction (α = 0.01), p-values between 0.01–0.05 should no longer be interpreted as statistically significant. The wording should therefore reflect exploratory rather than confirmatory interpretation.

1. Results – 3.0 m/s Entry Velocity (pp. 8–9; Table 2 interpretation)

Examples:

• Transition SFh (p = 0.05)
• Pickup 2 SFh (p = 0.06)
• Pickup 2 SL (p = 0.07)
• Step acceleration variables reported at p = 0.02

Suggested correction direction:
Please avoid wording implying confirmed between-group differences and instead describe these outcomes as the following:

• “showing tendencies,”
• “demonstrating moderate effects despite not reaching the adjusted threshold,”
• or “descriptive differences.”

Reason for revision:
The current phrasing occasionally overstates the statistical certainty of findings relative to the corrected alpha threshold.

1. Discussion Section (pp. 10–12)

Several interpretations are currently based on findings exceeding the adjusted α threshold and may therefore benefit from more cautious phrasing.

Suggested correction direction:
Please soften these interpretations using formulations such as:

• “may suggest,”
• “appeared to show,”
• “demonstrated a tendency toward,”
  particularly where referenced results correspond to p-values > 0.01.

Reason for revision:
This will improve methodological consistency between the statistical correction procedure and the interpretation of the findings while preserving the practical relevance of the observed trends.

These are relatively minor interpretative revisions and do not require additional analyses. The manuscript is otherwise substantially improved and presents a valuable contribution to the literature on pickup acceleration mechanics.

Sincerely

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors,

The manuscript has improved meaningfully over the previous version. The revised text now makes it clearer that the fast and slow comparisons are intended as descriptive rather than inferential, applies a Bonferroni-adjusted alpha of 0.01, expands the description of step identification and reliability, and acknowledges the proxy nature of the estimated force variables and the main limitations of the tethered system. The topic remains relevant and potentially valuable for applied sprint biomechanics, and the step-level approach across two entry velocities is a clear strength. The study also makes a useful contribution by addressing a relatively underexplored performance situation in team-sport athletes. However, some scientific concerns still remain. The central analytical limitation is only partially resolved: participants are still grouped by maximal acceleration and then compared using acceleration-related variables, including step acceleration and estimated step horizontal force. The manuscript now acknowledges this appropriately in the limitations, but the interpretative language should remain consistently cautious throughout, because the study is better framed as describing associations than establishing true determinants. This is especially important given that the title still refers to "determinants".

A second issue is statistical consistency. The manuscript states that the corrected alpha threshold is 0.01, yet parts of the abstract and narrative interpretation still refer to p≤0.05 or discuss trends above the corrected threshold in ways that may overstate the strength of the evidence. The abstract, results, discussion, and conclusion should be fully aligned with the adjusted significance criterion and should clearly distinguish statistically significant findings from descriptive trends.

The methods are clearer than before, but the equations and terminology still need tighter biomechanical clarification. In particular, the expression "SFh = body weight × Sa" remains potentially confusing unless the intended quantity is mass rather than weight. Likewise, the notation for Sa and Sv would benefit from a cleaner and more explicit presentation to ensure full reproducibility.

The added reliability and validity context is helpful, but it is still not entirely clear whether reliability has been demonstrated directly for all step-level derived variables central to this paper, rather than mainly for the broader step-selection process and outputs such as amax, vmax, and split times. A brief clarification on this point would strengthen confidence in the step-level inferences.

Overall, I consider the manuscript substantially improved and potentially publishable. The remaining concerns appear addressable through one further focused revision aimed at tightening the interpretative framework, aligning the statistical narrative with the corrected threshold, and clarifying the variable definitions.

Kind regards,

Author Response

Please see the attachment.

Author Response File: Author Response.pdf