Comparison of intra-session reliability of force-velocity-power variables between a horizontal dynamic leg press device and vertical jump tests

Takuya Nishioka; Shota Yamaguchi; Daiki Hajima; Yasuhiro Kunita; Takayuki Inami

doi:10.1371/journal.pone.0331671

Peer Review History

Original SubmissionMay 2, 2025
9 Jul 2025 Decision Letter - Julio Alejandro Henriques da Costa, Editor Dear Dr. Inami, Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. Please submit your revised manuscript by Aug 23 2025 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org . When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file. A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'. 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We look forward to receiving your revised manuscript. Kind regards, Julio Alejandro Henriques Castro da Costa Academic Editor PLOS ONE Journal requirements: When submitting your revision, we need you to address these additional requirements. 1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf 2. Please include a copy of Table 1 and 2 which you refer to in your text on page 11 and 12. 3. Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice. Additional Editor Comments (if provided): [Note: HTML markup is below. Please do not edit.] Reviewers' comments: Reviewer's Responses to Questions Comments to the Author 1. Is the manuscript technically sound, and do the data support the conclusions? Reviewer #1: Yes Reviewer #2: Yes ******** 2. Has the statistical analysis been performed appropriately and rigorously? -->?> Reviewer #1: Yes Reviewer #2: Yes ****** 3. Have the authors made all data underlying the findings in their manuscript fully available??> The PLOS Data policy Reviewer #1: Yes Reviewer #2: Yes ****** 4. Is the manuscript presented in an intelligible fashion and written in standard English??> Reviewer #1: Yes Reviewer #2: Yes ****** Reviewer #1: The manuscript is well-structured, coherent, and addresses a relevant topic in the context of neuromuscular performance assessment. The proposed HDLPD method appears promising, and the results indicate good reliability. To further strengthen the manuscript and support the conclusions drawn, I recommend a few minor additions: A brief mention justifying the sample size, such as through a power analysis, would be useful, even though the number of participants appears reasonable in the context of a reliability study. It might also be helpful to note potential limitations regarding the generalizability of the results, as the sample consists exclusively of elite male athletes. The comparison between the reliability of the HDLPD method and other tests (e.g., jump-based tests) is interesting but is not supported by a direct statistical comparison of the ICC coefficients. While not essential, adding such an analysis or phrasing the claims more cautiously could strengthen the argument. Regarding the conclusion related to the safety of the HDLPD method, the current formulation is persuasive but relies more on theoretical reasoning than on direct measurements. A more reserved formulation or an additional reference could improve clarity. These are minor adjustments and do not affect the overall validity of the study. However, they could enhance the manuscript’s coherence and scientific rigor. Congratulations to the authors on an interesting and well-conducted study. Reviewer #2: 1. Methodological Enhancements Required (1) Device calibration protocols must be explicitly stated in the Methods section. Specify the sampling frequency of force plates (e.g., 1000 Hz) and the cutoff frequency for low-pass filtering (e.g., 20 Hz Butterworth filter). (2) Clarify the rationale for selecting 100-200% body weight loads. Provide reference to pilot testing or existing literature supporting this range for hockey athletes. (3) Detail the force-velocity curve fitting algorithm. State whether linear or polynomial regression was applied and justify the choice. 2. Statistical Reporting Improvements (1) Table 1 should include both absolute (SEM in Newtons) and relative (CV%) reliability metrics for force variables to comply with sports science reporting standards. (2) Figure 2 needs error bars for individual data points when displaying mean force-velocity profiles across loads. (3) Report exact p-values rather than thresholds (e.g., p=0.032 instead of p<0.05) for all pairwise comparisons. 3. Discussion Limitations to Address (1) The discussion overstates HDLPD's superiority without biomechanical evidence. Modify claims to reflect that reliability differences may stem from joint angle specificity (knee flexion at 90° in HDLPD vs. variable angles in jumps) rather than inherent device superiority. (2) Acknowledge the sample limitation by adding: "Results may not generalize to female athletes or sports requiring greater vertical force production (e.g., basketball)." 4. Ethical Compliance Note (1) Ensure the Ethics Statement includes the institutional review board approval number and date (currently missing in Methods). (2) Confirm in the Data Availability Statement whether raw force-time data will be shared via repository (e.g., Figshare) or available upon request. ****** what does this mean? ). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy Reviewer #1: No Reviewer #2: No ******** [NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.] While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/ . PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. 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Revision 1
31 Jul 2025 Author Response Thank you for the opportunity to resubmit our manuscript entitled, “Comparison of intra-session reliability of force-velocity-power variables between a horizontal dynamic leg press device and vertical jump tests.” We have carefully reviewed the reviewers’ comments and revised the manuscript accordingly. All necessary changes have been made, and detailed responses to each comment are provided below. We hope the revised manuscript now meets the criteria for publication in your journal. Reviewer #1: The manuscript is well-structured, coherent, and addresses a relevant topic in the context of neuromuscular performance assessment. The proposed HDLPD method appears promising, and the results indicate good reliability. To further strengthen the manuscript and support the conclusions drawn, I recommend a few minor additions: Answer: Thank you for your valuable comments. Please find our detailed responses to each of your suggestions below. A brief mention justifying the sample size, such as through a power analysis, would be useful, even though the number of participants appears reasonable in the context of a reliability study. Answer: As you suggested, we have added an explanation regarding the sample size justification and included an appropriate reference, as follows: “Sample size calculations were performed using GPower software (version 3.1.9.6, Düsseldorf, Germany) to determine the number of participants required to assess reliability [12]. Based on a detected reliability of 0.9, a minimal acceptable reliability of 0.5, a significance level of 0.05, and a power of 0.95, the required sample size was calculated to be 17 participants. Accordingly, 19 male field hockey players (age: 19.6 ± 1.1 years, height: 173.0 ± 5.9 cm, body mass [BM]: 61.8 ± 6.5 kg, mean ± SD) were recruited to participate in this study” (lines 77–82) It might also be helpful to note potential limitations regarding the generalizability of the results, as the sample consists exclusively of elite male athletes. Answer: As you suggested, we have added a statement regarding the limitation of the study's generalizability. (lines 259–261) The comparison between the reliability of the HDLPD method and other tests (e.g., jump-based tests) is interesting but is not supported by a direct statistical comparison of the ICC coefficients. While not essential, adding such an analysis or phrasing the claims more cautiously could strengthen the argument. Answer: To the best of our knowledge, statistical tests for directly comparing reliability metrics (e.g., ICCs) are not implemented in commonly used statistical software such as SPSS, nor have they been widely applied in previous studies. Therefore, we compared the reliability between the HDLPD and vertical jump tests based on the interpretation of ICC values and sensitivity. Specifically, we considered an ICC greater than 0.90 as indicating excellent reliability, which we interpreted as higher than a “good” ICC ranging from 0.75 to 0.90. This approach to interpreting and comparing ICC values is consistent with those used in previous studies (1, 2). 1. Katoh M, Yamasaki H. Comparison of reliability of isometric leg muscle strength measurements made using a hand‑held dynamometer with and without a restraining belt. J Phys Ther Sci. 2009;21(1):37‑42. doi:10.1589/jpts.21.37. 2. Wei X, Zheng X, Zhu H, et al. Comparison of Intrasession Reliability and Sensitivity Across Different Deceleration-Test Results in Male and Female Soccer Players. Int J Sports Physiol Perform. 2025;20(6):779-785. doi:10.1123/ijspp.2024-0432. Regarding the conclusion related to the safety of the HDLPD method, the current formulation is persuasive but relies more on theoretical reasoning than on direct measurements. A more reserved formulation or an additional reference could improve clarity. Answer: As you suggested, we have removed the description regarding the safety of the HDLPD from the manuscript. (lines 33 and 276) These are minor adjustments and do not affect the overall validity of the study. However, they could enhance the manuscript’s coherence and scientific rigor. Congratulations to the authors on an interesting and well-conducted study. Answer: Thank you for your valuable comment. Your feedback was invaluable in strengthening our manuscript. We hope that the revisions meet your expectations. Reviewer #2: 1. Methodological Enhancements Required (1) Device calibration protocols must be explicitly stated in the Methods section. Specify the sampling frequency of force plates (e.g., 1000 Hz) and the cutoff frequency for low-pass filtering (e.g., 20 Hz Butterworth filter). Answer: The sampling frequency of force plates and the HDLPD were 1,000 and 200 Hz, respectively, and the cutoff frequency for low-pass filtering was 50 Hz, as described in the Materials and methods section. For the HDLPD, the upper limit of the sampling rate was relatively low (200 Hz), and the raw data exhibited minimal noise. Given this characteristic, a low-pass filter was not applied to the HDLPD data to avoid over-smoothing. Accordingly, the cutoff frequency for the HDLDP was not specified. (2) Clarify the rationale for selecting 100-200% body weight loads. Provide reference to pilot testing or existing literature supporting this range for hockey athletes. Answer: In our pilot testing, all participants were able to complete the leg press movement with a 200% body weight (BW) load. Furthermore, this load range corresponds to the typical load range observed in vertical jumps. Therefore, we selected 100–200% BW loads for the HDLPD in this study. We have added the following explanation to the manuscript: “In our pilot testing, all participants successfully performed the leg press at 200% BW. Furthermore, this load range corresponds to the forces typically observed during vertical jumps [3]; therefore, 100–200% BW loads were selected for the HDLPD in the present study.” (lines 110–113) (3) Detail the force-velocity curve fitting algorithm. State whether linear or polynomial regression was applied and justify the choice. Answer: We did not perform force–velocity curve fitting in the present study; instead, we reported the measured peak and mean values of force and velocity. Please refer to Tables 1 and 2. 2. Statistical Reporting Improvements (1) Table 1 should include both absolute (SEM in Newtons) and relative (CV%) reliability metrics for force variables to comply with sports science reporting standards. Answer: The SEM and CV values are already included; please refer to Tables 1 and 2. (2) Figure 2 needs error bars for individual data points when displaying mean force-velocity profiles across loads. Answer: As mentioned above, we did not create Figure 2 or include force-velocity profiles in the current study. (3) Report exact p-values rather than thresholds (e.g., p=0.032 instead of p<0.05) for all pairwise comparisons. Answer: Since reliability metrics (e.g., ICC and CV) cannot be directly compared using statistical tests, p-value–based statistical analysis was not performed. 3. Discussion Limitations to Address (1) The discussion overstates HDLPD’s superiority without biomechanical evidence. Modify claims to reflect that reliability differences may stem from joint angle specificity (knee flexion at 90° in HDLPD vs. variable angles in jumps) rather than inherent device superiority. Answer: As you suggested, we have added a discussion noting that differences in reliability may be attributable to variations in leg extension range of motion, as follows: “Additionally, in the HDLPD, the range of motion during leg extension is fixed by the device for each trial, whereas in vertical jump movements, some degree of variation in leg extension range of motion is inevitable [3]. This restriction imposed by the HDLPD may have further contributed to minimizing biological variability among participants.” (lines 232–236) (2) Acknowledge the sample limitation by adding: “Results may not generalize to female athletes or sports requiring greater vertical force production (e.g., basketball).” Answer: In response to your suggestion, we have added the following sentence: “Consequently, the results may not be applicable to female athletes or to sports that demand greater vertical force production, such as basketball.” (lines 259–261) 4. Ethical Compliance Note (1) Ensure the Ethics Statement includes the institutional review board approval number and date (currently missing in Methods). Answer: As you suggested, we have included the institutional review board approval number and date in the manuscript. (lines 89–90) (2) Confirm in the Data Availability Statement whether raw force-time data will be shared via repository (e.g., Figshare) or available upon request. Answer: We intend to provide the raw force–time data to readers upon request. This has been added to the data availability information. Attachments Attachment Submitted filename: Response_to_Reviewers.docx* https://doi.org/10.1371/journal.pone.0331671.r002
20 Aug 2025 Decision Letter - Julio Alejandro Henriques da Costa, Editor Comparison of intra-session reliability of force-velocity-power variables between a horizontal dynamic leg press device and vertical jump tests PONE-D-25-21984R1 Dear Dr. Inami, We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements. Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication. An invoice will be generated when your article is formally accepted. Please note, if your institution has a publishing partnership with PLOS and your article meets the relevant criteria, all or part of your publication costs will be covered. Please make sure your user information is up-to-date by logging into Editorial Manager at Editorial Manager® and clicking the ‘Update My Information' link at the top of the page. For questions related to billing, please contact billing support . If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org. Kind regards, Julio Alejandro Henriques Castro da Costa Academic Editor PLOS ONE Additional Editor Comments (optional): Reviewers' comments: Reviewer's Responses to Questions Comments to the Author Reviewer #1: All comments have been addressed Reviewer #2: All comments have been addressed ******** 2. Is the manuscript technically sound, and do the data support the conclusions??> Reviewer #1: (No Response) Reviewer #2: Yes ****** 3. Has the statistical analysis been performed appropriately and rigorously? -->?> Reviewer #1: (No Response) Reviewer #2: Yes ****** 4. Have the authors made all data underlying the findings in their manuscript fully available??> The PLOS Data policy Reviewer #1: (No Response) Reviewer #2: Yes ****** 5. Is the manuscript presented in an intelligible fashion and written in standard English??> Reviewer #1: (No Response) Reviewer #2: Yes ****** Reviewer #1: (No Response) Reviewer #2: The manuscript presents a well-conducted reliability study with appropriate methodology and comprehensive statistical analysis. The authors have adequately addressed all reviewer concerns and the findings provide valuable practical insights for sports science practitioners. I recommend acceptance. ****** what does this mean? ). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy Reviewer #1: No Reviewer #2: No ******** https://doi.org/10.1371/journal.pone.0331671.r003
Formally Accepted
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