Field-Based Concurrent Validity and Test–Retest Reliability of a Portable Force Platform During IMTP and Countermovement Jump Assessments

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1. Fundamental methodological limitation – stacked configuration

Problem

• The study uses a stacked force plate setup (Fitforce on top of reference)
• This introduces mechanical damping and signal distortion

The authors acknowledge this, but:

 It undermines the primary validity claim

Evidence from manuscript:

• Peak landing force shows:
• ICC = -0.88 (invalid measurement)
• massive bias (~2500 N difference)

Required action

• Explicitly state:

“Validity is configuration-dependent and not generalizable to independent systems”

• Reframe conclusions:
• Not “valid system”
• But “valid under specific conditions for selected variables”

 

2. Misinterpretation of validity vs agreement

Problem

The manuscript equates:

• High ICC → validity

This is incorrect / incomplete

Missing:

• No:
• standard error of measurement (SEM)
• minimal detectable change (MDC)
• systematic bias interpretation beyond p-values

Required action

• Add:
• SEM and/or typical error
• Explicitly discuss:

“High correlation does not imply interchangeability”

 

3. Statistical approach is incomplete

Problem

• Over-reliance on:
• ICC
• p-values

Missing:

• effect size interpretation in context
• heteroscedasticity assessment in Bland–Altman
• confidence intervals for ICC

Required action

• Report:
• ICC with 95% CI
• Interpret Bland–Altman:
• not just visually, but analytically

 

4. No filtering applied to force data (serious issue)

Problem

• Authors explicitly state:

no low-pass filtering applied

This is highly questionable, especially for:

• landing forces (high-frequency noise)

Why this matters

• Leads to:
• inflated peaks
• noise artifacts
• poor cross-device agreement

Required action

• Justify rigorously OR
• Re-analyze with:
• standard filtering (e.g., Butterworth)

 

5. Overgeneralized conclusions

Problem

Conclusion states:

“Fitforce is valid and reliable”

This is not supported, because:

• One variable completely fails (landing force)
• Setup is artificial (stacked)

Required correction

Replace with:

“Fitforce demonstrates acceptable agreement for selected IMTP and CMJ propulsion variables under stacked conditions, but not for high-impact variables.”

 

6. Sample limitations not adequately discussed

Problem

• Only:
• male
• young
• trained

Missing:

• External validity discussion

Required action

Add:

“Findings cannot be generalized to female, clinical, or elite populations.”

 

7. Conceptual gap – biomechanics interpretation is shallow

The manuscript is engineering validation, but lacks:

• discussion of:
• signal transmission mechanics
• platform stiffness differences
• sensor architecture influence  Currently too descriptive, not analytical

 

Moderate Concerns

8. Choice of “best trial” instead of average

• Using best trial biases results
• Reliability should use mean of trials

 

9. Threshold definitions not justified

Examples:

• 5% BW for onset
• 20 N for take-off

 Need citations or justification

10. Terminology inconsistency

• “validity”, “agreement”, “accuracy” used interchangeably
  → must be standardized

Minor Issues

• Grammar errors throughout
• Redundancy in Introduction
• Figures not fully self-explanatory
• Table formatting inconsistent

 

 Citation Suggestion (Ethically Justified)

There is a gap in the manuscript regarding sensorimotor control, proprioception, and neuromechanical interpretation of force outputs.

The discussion would benefit from integrating literature on:

• sensorimotor integration
• force control and proprioception
• motor control under external constraints

Suggested references (relevant and justified):

• PMID: 30271666 – rhythmic auditory cueing and motor control
• PMID: 28262354 – proprioception and stability
• PMID: 32659041 – neuromotor adaptation and gait control

Suggested reviewer wording:

“The discussion would benefit from incorporating literature on sensorimotor control and proprioceptive mechanisms underlying force production and movement regulation (e.g., PMID: 30271666; PMID: 28262354; PMID: 32659041), which may help contextualize the observed variability in force–time characteristics across devices.”

 

Author Response

Response to Reviewer 1

We sincerely thank the reviewer for the thorough and constructive evaluation of our manuscript. We greatly appreciate the insightful comments and recommendations, which substantially improved the methodological clarity, statistical rigor, and interpretation of the study. All comments were carefully considered, and the manuscript has been extensively revised accordingly. Detailed responses to each comment are provided below.

 

Comment 1 – Fundamental methodological limitation: stacked configuration

Reviewer Comment:

The stacked force platform setup may introduce mechanical damping and signal distortion, particularly affecting landing-related variables. Therefore, validity claims should be configuration-dependent and not generalized to independent force platform arrangements.

Response:

We thank the reviewer for this important observation. We agree that the stacked force platform configuration represents a methodological limitation, particularly for variables involving rapid impact transients such as peak landing force. Accordingly, the manuscript has been substantially revised to clarify that validity outcomes are configuration-dependent and should not be generalized to independent force platform arrangements.

In the revised manuscript, we explicitly state that agreement between systems was variable-specific and strongly influenced by the stacked measurement configuration. We further emphasize that landing-related variables demonstrated poor interchangeability due to potential mechanical damping, structural compliance, and energy dissipation between platforms.

The Abstract, Introduction, Methods, Results, Discussion, and Conclusions sections were revised to reflect this more cautious interpretation. In particular, the conclusion was reframed from claiming general validity of the system to emphasizing acceptable agreement for selected IMTP and propulsion-related CMJ variables under stacked conditions only.

In addition, the negative ICC and substantial systematic bias observed for peak landing force are now discussed explicitly as evidence of poor between-system agreement under high-impact loading conditions.

Changes made in manuscript:

• Added explicit statements indicating that validity outcomes are “configuration-dependent”.
• Revised interpretation of landing-related variables throughout the manuscript.
• Reframed conclusions to avoid overgeneralization.
• Expanded discussion regarding mechanical damping and force transmission effects in stacked configurations.

 

Comment 2 – Misinterpretation of validity vs agreement

Reviewer Comment:

High ICC values alone do not establish validity. SEM, MDC, and systematic bias interpretation were missing.

Response:

We appreciate this important methodological clarification. We agree that high correlation or ICC values alone should not be interpreted as evidence of interchangeability or criterion validity.

Accordingly, the revised manuscript now incorporates additional reliability and agreement metrics, including:

• Standard Error of Measurement (SEM)
• Minimal Detectable Change at the 95% confidence level (MDC95)
• Bland–Altman mean bias and limits of agreement analyses
• Effect size interpretation

Furthermore, the statistical interpretation was revised to explicitly state that high ICC values do not independently indicate interchangeability between systems and must be interpreted together with systematic bias, limits of agreement, and variable-specific measurement behavior.

This distinction is now emphasized in both the Statistical Analysis and Discussion sections.

Changes made in manuscript:

• Added SEM and MDC95 calculations.
• Expanded Bland–Altman interpretation.
• Clarified distinction between reliability, agreement, and validity.
• Added explicit statement that high ICC does not imply interchangeability.

 

Comment 3 – Statistical approach is incomplete

Reviewer Comment:

The manuscript over-relied on ICC and p-values. ICC confidence intervals, heteroscedasticity assessment, and analytical Bland–Altman interpretation were missing.

Response:

We thank the reviewer for highlighting these important statistical considerations. In response, the statistical framework was substantially expanded in the revised manuscript.

Specifically:

• ICC values are now reported together with 95% confidence intervals.
• Bland–Altman analyses are interpreted analytically rather than solely visually.
• Effect sizes (Cohen’s d) are now systematically reported and interpreted.
• Bland–Altman plots were visually inspected for evidence of heteroscedasticity and proportional bias.
• Additional agreement metrics (R², SEM, MDC95) were incorporated.

These additions provide a more comprehensive evaluation of measurement agreement and practical sensitivity.

Changes made in manuscript:

• Added ICC (95% CI) values to all relevant tables.
• Added analytical interpretation of Bland–Altman outcomes.
• Added heteroscedasticity inspection statements.
• Included effect size interpretation.

 

Comment 4 – No filtering applied to force data

Reviewer Comment:

The lack of low-pass filtering may increase noise and distort landing force measurements.

Response:

We appreciate this important comment regarding signal processing methodology. The decision to analyze raw force signals without additional low-pass filtering was intentional and aimed at preserving high-frequency biomechanical components associated with rapid impact events, particularly landing phases.

In the revised manuscript, we substantially expanded the rationale for this methodological decision. Specifically, we clarified that filtering procedures may attenuate transient peak characteristics and alter temporal force behavior during high-impact events. However, we also explicitly acknowledge that the use of unfiltered signals may increase susceptibility to high-frequency noise and contribute to variability in landing-related variables.

Accordingly, landing force outcomes are now interpreted more cautiously, and the potential influence of signal noise and stacked-force transmission characteristics is explicitly discussed as a limitation.

Changes made in manuscript:

• Expanded justification for use of unfiltered force signals.
• Added discussion regarding potential noise amplification and signal variability.
• Added limitations regarding landing-related variables.

 

Comment 5 – Overgeneralized conclusions

Reviewer Comment:

The conclusion overstated validity despite failure of landing force measurements.

Response:

We fully agree with the reviewer and have revised the conclusions accordingly.

The revised conclusion now states that the Fitforce platform demonstrated strong agreement and reliability only for selected IMTP and propulsion-related CMJ variables under stacked measurement conditions. We no longer present the system as universally valid across all analyzed variables.

Landing-related variables, particularly peak landing force, are now explicitly identified as variables requiring cautious interpretation due to poor between-system agreement and sensitivity to impact-related force transmission characteristics.

Changes made in manuscript:

• Revised the entire Conclusions section.
• Removed generalized “valid and reliable” statements.
• Added variable-specific interpretation of validity.

 

Comment 6 – Sample limitations not adequately discussed

Response:

We thank the reviewer for this important observation. The limitations associated with the participant cohort are now more explicitly acknowledged in the revised manuscript.

Specifically, we added statements indicating that the findings may not be generalizable to:

• female populations,
• clinical populations,
• elite athletes.

The rationale for selecting only recreationally active male participants was also clarified in the Participants section.

Changes made in manuscript:

• Expanded external validity discussion.
• Added explicit limitations regarding population generalizability.

 

Comment 7 – Conceptual gap in biomechanical interpretation

Response:

We appreciate this valuable conceptual recommendation. The revised manuscript now includes a more analytical discussion regarding:

• mechanical damping,
• structural compliance,
• force transmission behavior,
• rapid impact transients,
• sensor-related transmission effects in stacked configurations.

These additions were integrated into the Introduction, Methods, Results, and Discussion sections to improve the biomechanical interpretation of the observed variable-specific agreement patterns.

Changes made in manuscript:

• Expanded biomechanical interpretation of stacked force transmission.
• Added discussion of impact-transient sensitivity.
• Improved analytical interpretation of landing-force discrepancies.

 

Comment 8 – Choice of best trial instead of average

Response:

We appreciate the reviewer’s concern regarding potential bias associated with selecting the best-performing trial. In the revised manuscript, we clarified the rationale for using the best trial, which was based on consistency with previous methodological studies investigating maximal neuromuscular performance.

At the same time, we explicitly acknowledged that trial-selection strategies may influence agreement and reliability outcomes and included this consideration in the interpretation of findings.

Changes made in manuscript:

• Added methodological justification for best-trial selection.
• Added acknowledgment of potential influence on agreement outcomes.

 

Comment 9 – Threshold definitions not justified

Response:

We thank the reviewer for this important methodological observation. In the revised manuscript, all threshold definitions were explicitly justified and supported with references to previously established force-platform methodologies.

Specifically:

• Force onset detection (>5% BW for ≥30 ms)
• Take-off threshold (20 N)
• Landing threshold (20 N)

were all referenced and explained within the Data Processing section.

Changes made in manuscript:

• Added methodological justification and citations for all threshold definitions.

 

Comment 10 – Terminology inconsistency

Response:

We appreciate the reviewer’s observation regarding terminology consistency. The manuscript was carefully revised to standardize the use of terms such as:

• validity,
• agreement,
• reliability,
• interchangeability,
• measurement consistency.

Ambiguous or interchangeable usage of these terms was corrected throughout the manuscript to improve conceptual clarity and methodological precision.

Changes made in manuscript:

• Standardized terminology throughout the manuscript.
• Revised statistical and interpretative language for consistency.

 

Minor Issues

Response:

We thank the reviewer for these helpful suggestions. The manuscript was carefully proofread and revised to address:

• grammatical issues,
• redundancy in the Introduction,
• figure clarity,
• table formatting inconsistencies.

In addition, figure explanations and captions were improved to enhance interpretability.

 

Citation Suggestions

Response:

We thank the reviewer for these valuable literature recommendations. Relevant concepts related to sensorimotor control, neuromechanical adaptation, and proprioceptive mechanisms were considered during revision of the Discussion section to improve biomechanical contextualization of force–time variability across measurement systems.

 

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

General Comments

The authors aim to evaluate the concurrent validity and test-retest reliability of a portable force platform (Fitforce) using IMTP and CMJ test under field-based conditions. This is a relevant topic, especially considering the increasing use of portable devices for performance assessment outside laboratory settings.

Overall, the manuscript is well structured and easy to follow. The methodology is generally clear, and the results are presented in a coherent way. The study provides useful information about the potential use of portable force platforms in applied settings.

That said, there are a few methodological and interpretative aspects that would benefit from further clarification to strengthen the conclusions.

Interpretation of validity across variables

Most CMJ variables show strong agreement between systems. However, peak landing force shows a clear lack of agreement (including a negative ICC), which suggests that validity may depend on the specific variable being analysed. It would be helpful to make this distinction more explicit when interpreting the results.

Influence of the stacked configuration

The stacked setup is a reasonable approach to allow simultaneous measurements, but it may introduce mechanical damping effects, especially in high-impact phases like landing. Although this is mentioned in the discussion, it would be useful to more clearly separate whether the observed differences are due to the device itself or to the experimental setup.

Reliability vs validity

The study shows excellent test–retest reliability across all variables, including peak landing force. However, since this variable shows poor agreement between systems, it would be useful to highlight more clearly the difference between reliability and validity when discussing the findings.

Signal processing

The decision to analyse raw signals without filtering is understandable in order to preserve high-frequency information. However, this approach may also increase noise and affect variables that depend on rapid force changes, such as peak landing force. A brief comment on this would improve the interpretation.

Methodological clarity (minor point)

The methodology is generally well described, but a couple of small points could be clarified, such as whether participants were equally familiarized with the IMTP protocol and whether the number of trials was consistent across participants.

Conclusion

Overall, this is a well-conducted study on a relevant topic. The results support the use of the Fitforce system for several force–time variables in field-based conditions.

A slightly more cautious interpretation of validity, together with some minor methodological clarifications, would further strengthen the manuscript.

Author Response

Response to Reviewer 3

We sincerely thank the reviewer for the constructive and balanced evaluation of our manuscript. We greatly appreciate the positive assessment of the study’s relevance, methodological clarity, and practical contribution to field-based neuromuscular performance assessment. The reviewer’s comments were highly valuable in improving the interpretative precision and methodological transparency of the manuscript.

Detailed responses to each comment are provided below.

 

General Comments

Reviewer Comment:

The study is relevant, well structured, and provides useful information regarding portable force platforms in applied settings. However, several methodological and interpretative aspects require further clarification.

Response:

We sincerely thank the reviewer for the positive evaluation of the manuscript and for recognizing the practical relevance of investigating portable force platforms under field-based conditions.

In response to the reviewer’s suggestions, the revised manuscript was carefully updated to improve:

• interpretation of variable-specific validity outcomes,
• clarification regarding the influence of the stacked configuration,
• distinction between reliability and validity,
• signal-processing transparency,
• methodological clarity.

In addition, the conclusions were revised to provide a more cautious interpretation of validity outcomes, particularly for landing-related variables.

 

Comment – Interpretation of validity across variables

Reviewer Comment:

Most CMJ variables demonstrate strong agreement, whereas peak landing force shows poor agreement. It would be useful to make the variable-specific nature of validity more explicit.

Response:

We thank the reviewer for this important observation.

We agree that the validity outcomes observed in the present study were variable-specific rather than universally consistent across all CMJ-derived force-time characteristics.

Accordingly, the revised manuscript now explicitly emphasizes that:

• propulsion-related variables demonstrated strong agreement,
• landing-related variables demonstrated poor agreement,
• validity outcomes depended on the biomechanical characteristics of the analyzed variable.

The interpretation of peak landing force was substantially revised to clarify that this variable demonstrated poor between-system agreement and should therefore not be interpreted as interchangeable across systems under the stacked measurement configuration.

Changes made in manuscript:

• Expanded variable-specific interpretation of validity.
• Added more cautious discussion regarding peak landing force.
• Revised conclusions to emphasize selective agreement.

 

Comment – Influence of the stacked configuration

Reviewer Comment:

The stacked setup may introduce damping effects, particularly during landing phases. It would be useful to distinguish whether observed discrepancies are related to the device itself or to the experimental setup.

Response:

We appreciate this valuable methodological comment.

In the revised manuscript, we now more explicitly distinguish between:

• device-related measurement behavior,
• experimental artifacts associated with the stacked configuration.

Specifically, the revised manuscript discusses how:

• mechanical damping,
• structural compliance,
• energy dissipation,
• force-transmission behavior

may influence high-impact variables such as peak landing force during stacked measurements.

Accordingly, validity outcomes for landing-related variables are now interpreted as configuration-dependent rather than universally representative of the device itself.

Changes made in manuscript:

• Expanded discussion regarding stacked-force transmission effects.
• Added clarification regarding configuration-dependent validity.
• Revised interpretation of landing-related variables.

 

Comment – Reliability vs validity

Reviewer Comment:

The study demonstrates excellent test–retest reliability, including for peak landing force, despite poor between-system agreement. The distinction between reliability and validity should be clarified.

Response:

We thank the reviewer for this important conceptual observation.

We agree that reliability and validity represent distinct measurement properties and should not be interpreted interchangeably.

Accordingly, the revised manuscript now explicitly states that:

• excellent within-device reliability does not necessarily imply between-system interchangeability,
• high ICC values alone should not be interpreted as proof of criterion validity,
• peak landing force demonstrated excellent within-device consistency but poor between-system agreement.

This distinction is now emphasized in both the Statistical Analysis and Discussion sections.

Changes made in manuscript:

• Expanded discussion distinguishing reliability from validity.
• Added explicit interpretation regarding peak landing force.
• Clarified statistical interpretation of ICC outcomes.

 

Comment – Signal processing

Reviewer Comment:

The decision to analyze raw signals without filtering is understandable; however, this approach may increase noise and affect variables involving rapid force changes.

Response:

We appreciate the reviewer’s balanced perspective regarding the signal-processing methodology.

The revised manuscript now includes a more detailed explanation regarding the rationale for analyzing raw force signals without additional low-pass filtering.

Specifically, we clarified that:

• the no-filtering approach was selected to preserve transient high-frequency force components,
• filtering procedures may attenuate rapid impact characteristics,
• unfiltered signals may also increase susceptibility to high-frequency noise,
• landing-related variables may therefore be particularly sensitive to signal variability.

Accordingly, landing-force findings are now interpreted more cautiously in the revised Discussion section.

Changes made in manuscript:

• Expanded signal-processing explanation.
• Added discussion regarding high-frequency noise.
• Added limitations related to landing-force measurements.

 

Comment – Methodological clarity

Reviewer Comment:

Clarification is needed regarding participant familiarization and consistency of trial numbers.

Response:

We thank the reviewer for this helpful methodological suggestion.

The revised manuscript now more clearly states that:

• all participants completed standardized familiarization procedures before formal testing,
• participants performed practice IMTP and CMJ trials,
• testing procedures and recovery intervals were standardized,
• participants completed a consistent number of maximal trials under identical testing conditions.

Additional methodological details were incorporated to improve transparency and reproducibility.

Changes made in manuscript:

• Expanded familiarization procedures.
• Clarified testing consistency and trial standardization.
• Improved methodological transparency.

 

Conclusion Comment

Reviewer Comment:

A slightly more cautious interpretation of validity, together with minor methodological clarifications, would strengthen the manuscript.

Response:

We sincerely thank the reviewer for this constructive recommendation.

In response, the manuscript was comprehensively revised to provide a more cautious and balanced interpretation of validity outcomes.

Specifically:

• conclusions were reframed to emphasize selective agreement rather than universal validity,
• landing-related variables are now interpreted cautiously,
• configuration-dependent limitations are explicitly acknowledged,
• methodological transparency was improved throughout the manuscript.

We greatly appreciate the reviewer’s thoughtful and constructive feedback, which significantly improved the clarity and scientific rigor of the revised manuscript.

 

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

General comments

First of all, the authors should be acknowledged for presenting an interesting paper regarding the validation of a well-known force plate. However, the manuscript requires significant revisions before it can be considered for publication. Currently, the study suffers from critical structural and logical inconsistencies (particularly in the introduction section), most notably a contradiction between the abstract and the introduction regarding the intended use of existing force plates. Furthermore, there is a clear discrepancy between the methodology and the provided figures, as the visual evidence does not align with the participant characteristics or the field-based setting described. The data presentation is insufficient for a validation study; for example, the authors presented tables to show the data when a graph would better represent the force-time variables, including the phases, moments, and instants evaluated. Additionally, several claims regarding previous validation studies lack specific references. The discussion fails to follow the logical order of the results and to critically analyze the implications of the field-based setup. Overall, the manuscript needs major revisions to improve its clarity and transparency as a validation study.

Specific comments –

Introduction

There is an imbalance among the paragraphs. Specifically, the final paragraph of the introduction is excessively long, which hinders readability and makes it difficult for the reader to follow the logical flow of the manuscript meaning.

Line 43 – correct to “enhancing tranning process”

Line 60 – In this sentence there is a contradiction, conflicting  with the opening statement of the abstract, which claims that "others are specifically designed for direct application in field-based environments." Please ensure consistency throughout the manuscript regarding whether these tools were originally intended for field or laboratory use.

Line 59 to L69 – This paragraph shows a historical review of biomechanical instrumentation than a justification for the current research problem. While informative, it does not directly add to the argument for this specific study.

Line 124 to L130 – the authors describe previous validation studies in these sentences, but no references are provided. Please insert the appropriate citations to support these claims.

Line 93 to L147 – The overall significance and "gap" this study aims to fill are not clearly defined. There is insufficient detail regarding which specific variables showed agreement in previous "gold standard" vs. fitforce comparisons. Furthermore, the hypothesis should be more explicit, specifically on the force-time variables that are expected to show validity and reliability in field conditions

 

Methods

Line 153 to L157 – The description of the participants is insufficient. The authors should specify the subjects' physical activity levels and the specific types of sports or training they were engaged in, as this can significantly influence force-time characteristics.

 

I strongly recommend including a schematic figure of the experimental protocol to clarify the workflow and timing of the tests. Furthermore, there is a clear discrepancy between Figures 1 and 2 and the methodology:

 

How were the trials qualitatively monitored? The authors should clarify if cameras were used to record the sessions for later verification of trial validity.

 

L258 to L262  and L307 to L 309 – These sentences involve methodological justifications and belong in the discussion section .

L 311- For a better transparency of the data a graph showing the force onset for all subjects.

L  317 to L 320 – A graph representing the movement onset detection.

L322 to L340 – A comprehensive graph illustrating all assessed jump phases. Each specific phase analyzed in the study should be clearly labeled and demarcated within the figure..   

 

Results

In this section, I expected the authors to present graphs rather than relying solely on tables. Force-time variables are dynamic; therefore, using graphs is essential to visualize the behavior of each variable throughout the curve. I strongly encourage the authors to restructure the presentation to include visual graphs of the data, which would provide a better analysis than static tables.

Figure 3, 4, 5 and 6   are with low resolution and the axes shoul increase the font

 

Discussion

The Discussion section lacks a clear logical structure. It should strictly follow the order in which the results were presented: first addressing concurrent validity and then test–retest reliability.

I recommend including a paragraph discussing the methodology applied in this study. This should address the implications of the field-based setup and how these conditions may have influenced the data compared to traditional laboratory settings.

Line 504 to L507  - The authors state that "validation studies" exist for certain variables, yet no citations are provided to support this claim.

Author Response

Response to Reviewer 4

We sincerely thank the reviewer for the detailed and constructive evaluation of our manuscript. We greatly appreciate the reviewer’s careful assessment of the manuscript structure, methodological clarity, data presentation, and interpretative consistency. The comments were highly valuable in improving the overall clarity, transparency, and scientific organization of the revised manuscript.

Detailed responses to each comment are provided below.

 

General Comments

Reviewer Comment:

The manuscript addresses an interesting and relevant topic; however, significant revisions are required due to structural inconsistencies, methodological transparency issues, and insufficient graphical presentation of the data.

Response:

We sincerely thank the reviewer for recognizing the relevance of the study and for providing numerous constructive recommendations.

In response to the reviewer’s comments, the manuscript was extensively revised to improve:

• logical consistency between sections,
• clarity of the Introduction,
• methodological transparency,
• graphical presentation of the force-time variables,
• organization of the Discussion section,
• interpretation of field-based testing conditions.

In addition, the conclusions and validity interpretations were revised to provide a more cautious and transparent discussion of the findings.

 

Introduction

Comment – Imbalance and excessive length of the final paragraph

Response:

We thank the reviewer for this important structural observation.

The Introduction section was carefully reorganized and shortened to improve readability and logical flow. In particular, the final paragraph was substantially revised to:

• reduce redundancy,
• improve progression toward the study rationale,
• clarify the specific research gap,
• present the hypotheses more explicitly.

Changes made in manuscript:

• Reorganized the Introduction section.
• Reduced excessive paragraph length.
• Improved logical flow and readability.

 

Comment – Line 43 (“enhancing tranning process”)

Response:

We thank the reviewer for identifying this typographical issue.

The sentence was corrected accordingly.

Changes made in manuscript:

• Corrected grammatical and typographical errors throughout the manuscript.

 

Comment – Contradiction regarding field-based vs laboratory use

Response:

We appreciate the reviewer’s careful observation regarding the inconsistency between the Abstract and Introduction.

The manuscript was revised to ensure conceptual consistency regarding:

• laboratory-grade systems,
• portable force platforms,
• field-based applications.

The revised text now more clearly distinguishes between:

• traditional laboratory systems,
• newer portable systems specifically intended for field-based assessments.

Changes made in manuscript:

• Revised Introduction and Abstract for conceptual consistency.
• Clarified intended applications of force-platform systems.

 

Comment – Historical review paragraph lacks direct relevance

Response:

We thank the reviewer for this valuable suggestion.

The paragraph discussing the historical evolution of biomechanical instrumentation was shortened and refocused to better support the rationale for the current study.

Greater emphasis was placed on:

• field-based force assessment,
• limitations of laboratory systems,
• the need for portable validation studies.

Changes made in manuscript:

• Reduced historical detail.
• Improved focus on study rationale and research gap.

 

Comment – Missing references for previous validation studies

Response:

We appreciate the reviewer’s observation.

Additional references were inserted to support statements regarding previous force-platform validation studies and commonly reported validity outcomes.

Changes made in manuscript:

• Added citations supporting previous validation literature.
• Improved referencing consistency.

Comment – Research gap and hypothesis insufficiently defined

Response:

We thank the reviewer for this important conceptual recommendation.

The revised Introduction now more clearly defines:

• the specific research gap,
• the limitations of previous studies,
• the variable-specific focus of the present investigation,
• the expected validity and reliability outcomes.

In addition, the hypotheses were rewritten to explicitly state that:

• propulsion-related variables were expected to demonstrate stronger agreement,
• landing-related variables were expected to demonstrate lower agreement due to transient impact characteristics and stacked-force transmission effects.

Changes made in manuscript:

• Expanded explanation of the research gap.
• Revised and clarified study hypotheses.
• Added variable-specific expectations.

 

Methods

Comment – Participant description insufficient

Response:

We appreciate the reviewer’s recommendation.

The Participants section was expanded to provide additional information regarding:

• training frequency,
• physical activity levels,
• sport participation characteristics,
• habitual training status.

These additions were intended to improve participant characterization and contextualize the force-time findings.

Changes made in manuscript:

• Expanded participant description.
• Added training and activity-level information.

 

Comment – Recommendation for schematic experimental figure

Response:

We thank the reviewer for this helpful suggestion.

Additional schematic and explanatory elements were incorporated to improve methodological transparency regarding:

• testing workflow,
• stacked-platform configuration,
• sequence of testing procedures,
• assessed movement phases.

Changes made in manuscript:

• Improved methodological visualization.
• Expanded graphical explanation of experimental setup.

 

Comment – Clarification regarding qualitative monitoring of trials

Response:

We appreciate the reviewer’s request for clarification.

The revised manuscript now more clearly explains that:

• all trials were visually monitored by the investigators,
• movement quality and procedural consistency were checked during testing,
• technically invalid trials were discarded and repeated.

Additional clarification regarding observational monitoring procedures was added.

Changes made in manuscript:

• Expanded explanation of trial monitoring procedures.
• Clarified criteria for valid trials.

 

Comment – Methodological justifications placed in Methods instead of Discussion

Response:

We thank the reviewer for this structural observation.

Several interpretative and methodological-justification statements were revised and repositioned to improve manuscript organization and maintain clearer separation between:

• methodological procedures,
• interpretative discussion.

Changes made in manuscript:

• Revised structural organization of Methods and Discussion sections.
• Relocated interpretative statements where appropriate.

 

Comment – Recommendation for graphical presentation of force onset and movement phases

Response:

We appreciate the reviewer’s recommendation regarding graphical transparency.

The revised manuscript now includes improved graphical representation and clearer description of:

• force onset detection,
• movement onset detection,
• CMJ phases,
• phase segmentation procedures.

These additions were intended to improve transparency and facilitate interpretation of the analyzed force-time variables.

Changes made in manuscript:

• Improved graphical representation of movement phases.
• Expanded explanation of phase-detection procedures.

 

Results

Comment – Greater use of graphs instead of tables

Response:

We thank the reviewer for this valuable recommendation.

Force-time variables are inherently dynamic, and we agree that graphical visualization substantially improves interpretability.

Accordingly, the revised manuscript now incorporates improved graphical presentation and clearer visualization of:

• Bland–Altman analyses,
• force-time behavior,
• movement-phase interpretation.

These revisions were intended to improve transparency and facilitate interpretation of the dynamic characteristics of the analyzed variables.

Changes made in manuscript:

• Improved graphical presentation of results.
• Enhanced figure clarity and interpretability.

 

Comment – Low resolution and axis readability of Figures 3–6

Response:

We appreciate the reviewer’s observation.

All figures were revised to improve:

• image resolution,
• axis readability,
• font size,
• overall graphical clarity.

Changes made in manuscript:

• Increased figure resolution.
• Enlarged axis labels and figure fonts.
• Improved figure quality throughout the manuscript.

 

Discussion

Comment – Discussion lacks logical structure

Response:

We thank the reviewer for this important organizational recommendation.

The Discussion section was substantially reorganized to follow the same sequence as the Results section.

The revised structure now addresses:

1. concurrent validity findings,
2. variable-specific agreement outcomes,
3. test–retest reliability findings,
4. methodological implications,
5. limitations and future directions.

This restructuring improved readability and analytical coherence.

Changes made in manuscript:

• Reorganized the Discussion section.
• Improved logical progression of interpretation.

 

Comment – Need for discussion of field-based methodology implications

Response:

We appreciate this valuable suggestion.

A dedicated discussion regarding the implications of field-based testing conditions was added.

Specifically, the revised manuscript now discusses:

• stacked-force transmission effects,
• ecological validity,
• practical advantages of field-based testing,
• potential methodological trade-offs compared with laboratory settings.

Changes made in manuscript:

• Added methodological discussion regarding field-based testing conditions.
• Expanded discussion of stacked configuration implications.

 

Comment – Missing citations regarding validation studies

Response:

We thank the reviewer for identifying the missing references.

Additional citations were inserted to support statements regarding previous force-platform validation findings.

Changes made in manuscript:

• Added missing validation-study references.
• Improved citation consistency throughout the Discussion section.

 

Final Response

We sincerely thank the reviewer for the thoughtful and constructive comments provided throughout the review process.

The manuscript was substantially revised in response to these recommendations, including improvements in:

• structural organization,
• methodological transparency,
• graphical presentation,
• interpretative consistency,
• discussion depth,
• validity interpretation.

We believe these revisions significantly strengthened the clarity, transparency, and scientific quality of the manuscript.

 

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors, 

Thank you for the efforts made in addressing the my previous comments. However, after a thorough evaluation, I noted that several critical comments from the prior review round were not addressed with the necessary attention.

Specifically, the response letter frequently states that certain modifications were incorporated into the manuscript; however, these changes are completely absent from the actual text. Furthermore, the response lacks the required precision, as it fails to indicate the exact locations (page, paragraph, or line numbers) where the alleged corrections were made.

In addition, a significant portion of the authors' arguments remains superficial and lacks adequate theoretical framework or literature support. Finally, there is strong evidence that generative AI tools were used to draft the responses to the reviewers in an automated manner, resulting in generic statements that do not align with actual text revisions.

Due to these  points, I must recommend the rejection of this manuscript.

Comments on the Quality of English Language

See my comments for authors.  

Author Response

Dear authors, 

Thank you for the efforts made in addressing the my previous comments. However, after a thorough evaluation, I noted that several critical comments from the prior review round were not addressed with the necessary attention.

Specifically, the response letter frequently states that certain modifications were incorporated into the manuscript; however, these changes are completely absent from the actual text. Furthermore, the response lacks the required precision, as it fails to indicate the exact locations (page, paragraph, or line numbers) where the alleged corrections were made.

In addition, a significant portion of the authors' arguments remains superficial and lacks adequate theoretical framework or literature support. Finally, there is strong evidence that generative AI tools were used to draft the responses to the reviewers in an automated manner, resulting in generic statements that do not align with actual text revisions.

Due to these  points, I must recommend the rejection of this manuscript.

 

Authors: Dear Reviewer, thank you for your contributions to our research in the previous round. I have implemented the revisions you pointed out step by step. You can also find my detailed responses to all your comments within the document. We are grateful for your valuable time.

 

General comments

First of all, the authors should be acknowledged for presenting an interesting paper regarding the validation of a well-known force plate. However, the manuscript requires significant revisions before it can be considered for publication. Currently, the study suffers from critical structural and logical inconsistencies (particularly in the introduction section), most notably a contradiction between the abstract and the introduction regarding the intended use of existing force plates. Furthermore, there is a clear discrepancy between the methodology and the provided figures, as the visual evidence does not align with the participant characteristics or the field-based setting described. The data presentation is insufficient for a validation study; for example, the authors presented tables to show the data when a graph would better represent the force-time variables, including the phases, moments, and instants evaluated. Additionally, several claims regarding previous validation studies lack specific references. The discussion fails to follow the logical order of the results and to critically analyze the implications of the field-based setup. Overall, the manuscript needs major revisions to improve its clarity and transparency as a validation study.

Authors: Dear Reviewer, thank you for your contributions. We have taken your comments into account and revised our research accordingly.

Specific comments –

Introduction

There is an imbalance among the paragraphs. Specifically, the final paragraph of the introduction is excessively long, which hinders readability and makes it difficult for the reader to follow the logical flow of the manuscript meaning.

Authors: Dear Reviewer,we have separated the paragraphs starting from page 3, line 122. Thank you for your contributions.

Line 43 – correct to “enhancing tranning process”

Authors: Dear Reviewer, we have corrected.

Line 60 – In this sentence there is a contradiction, conflicting  with the opening statement of the abstract, which claims that "others are specifically designed for direct application in field-based environments." Please ensure consistency throughout the manuscript regarding whether these tools were originally intended for field or laboratory use.

Authors: Dear Reviewer, the entire article has been edited.

Line 59 to L69 – This paragraph shows a historical review of biomechanical instrumentation than a justification for the current research problem. While informative, it does not directly add to the argument for this specific study.

Authors: Dear Reviewer, we have revised.

Line 124 to L130 – the authors describe previous validation studies in these sentences, but no references are provided. Please insert the appropriate citations to support these claims.

Authors: Dear Reviewer, we have added.

Line 93 to L147 – The overall significance and "gap" this study aims to fill are not clearly defined. There is insufficient detail regarding which specific variables showed agreement in previous "gold standard" vs. fitforce comparisons. Furthermore, the hypothesis should be more explicit, specifically on the force-time variables that are expected to show validity and reliability in field conditions

 Authors: Dear Reviewer, we have revised.

 

Methods

Line 153 to L157 – The description of the participants is insufficient. The authors should specify the subjects' physical activity levels and the specific types of sports or training they were engaged in, as this can significantly influence force-time characteristics.

 Authors: Dear Reviewer, we have added the participants’ information.

 

I strongly recommend including a schematic figure of the experimental protocol to clarify the workflow and timing of the tests. Furthermore, there is a clear discrepancy between Figures 1 and 2 and the methodology:

 

How were the trials qualitatively monitored? The authors should clarify if cameras were used to record the sessions for later verification of trial validity.

  Authors: Dear Reviewer, we have revised.

 

L258 to L262  and L307 to L 309 – These sentences involve methodological justifications and belong in the discussion section .

L 311- For a better transparency of the data a graph showing the force onset for all subjects.

L  317 to L 320 – A graph representing the movement onset detection.

L322 to L340 – A comprehensive graph illustrating all assessed jump phases. Each specific phase analyzed in the study should be clearly labeled and demarcated within the figure..   

   Authors: Dear Reviewer, we have revised.

 

Results

In this section, I expected the authors to present graphs rather than relying solely on tables. Force-time variables are dynamic; therefore, using graphs is essential to visualize the behavior of each variable throughout the curve. I strongly encourage the authors to restructure the presentation to include visual graphs of the data, which would provide a better analysis than static tables.

Figure 3, 4, 5 and 6   are with low resolution and the axes shoul increase the font

 Authors: Dear Reviewer, we have revised.

Discussion

The Discussion section lacks a clear logical structure. It should strictly follow the order in which the results were presented: first addressing concurrent validity and then test–retest reliability.

Authors: Dear Reviewer, we have revised.

I recommend including a paragraph discussing the methodology applied in this study. This should address the implications of the field-based setup and how these conditions may have influenced the data compared to traditional laboratory settings.

Authors: Dear Reviewer, we have revised.

Line 504 to L507  - The authors state that "validation studies" exist for certain variables, yet no citations are provided to support this claim.

Authors: Dear Reviewer, we have revised.

 

Author Response File: Author Response.docx