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Dear Authors,
Thank you for addressing the reviewers´ suggestions and the collaborative work during the review process.
Best regards.
[# PeerJ Staff Note - this decision was reviewed and approved by Mike Climstein, a PeerJ Section Editor covering this Section #]
I am happy with the current version of the manuscript.
The authors did a good job of reviewing and answering all comments made.
Thank you,
best regards.
.
.
Dear Authors,
Please revise the manuscript considering the reviewers´ suggestions.
Thank you.
Best regards.
1. The manuscript is written in clear English. However, some sentences could be more concise for better readability (e.g., Introduction lines 65–69 could be streamlined).
2. Minor grammatical inconsistencies were noted (e.g., "effect" vs. "affect" confusion in multiple sections).
3. It is recommended to have a final proofreading to ensure clarity and grammatical accuracy.
4. The references are appropriate and relevant, but additional citations in the discussion section (lines 303–309) would help link findings to broader literature.
5. Figures and tables are well presented, but Table 2 needs a clearer caption explaining abbreviations.
6. Figures are high quality and relevant. However, Figure 3 could include clearer labeling of axes.
7. It is recommended to add a brief explanation of the residual plots in Figure 2.
8. Ethical approval details are provided (lines 131–133), but it would be beneficial to explicitly state participant confidentiality measures.
9. The methodology is described with sufficient detail for replication, though the description of the Ridge Regression model could be expanded for clarity.
10. The use of Ridge Regression is a strength, but a brief justification for its application over alternative methods (e.g., stepwise regression) would improve the section.
11. The discussion effectively links results to prior literature but would benefit from further elaboration on practical implications (e.g., how coaches can apply findings).
12. Some conclusions (lines 357–360) need to be more conservative in wording to acknowledge study limitations.
13. Limitations are acknowledged (lines 348–355), but further elaboration on how future research could address variability in the Nordic exercise protocol would strengthen this section.
14. Minor grammatical and structural refinements for clarity.
15. Further justification of statistical methods.
16. More detailed discussion on practical applications and future research.
Needs improvement, see comments below in additional comments box.
Could be improved but adequate.
Could be improved but adequate.
Dear authors,
I appreciate the time and effort you have taken in amending the submission, however, many of the comments you have not addressed you still lack consistency on use of terminology, for instance you use NHC and NHE throughout the manuscript even though you suggest this has been removed, you are inconsistent with the use of abbreviations. Additionally, the scientific application of the magnitudes is neglected and requires further investigation. Moreover, the context of the findings needs further work, I would argue the changes suggested in sprint and jump time are not practically relevant and are likely within the error of the measurement.
please see comments below.
L39 – A study is inanimate, it cannot investigate. This grammatically incorrect there is no issue with the context of the study.
L47-53 – For correlations the p value is of less importance as it is highly impacted by the sample size. The magnitude is more important here, as you could have a non-significant, large relationship or a significant trivial relationship, obviously the former is more meaningful.
Cumming, G. (2014). The New Statistics: Why and How. Psychological Science, 25(1), 7-29. https://doi.org/10.1177/0956797613504966
https://rpsychologist.com/correlation/
L103 - A study is inanimate, it cannot examine. This grammatically incorrect there is no issue with the context of the study.
L104-106 – Why would an increase NHCbpa negatively affect performance? I assume an increase angle you mean reaches further excursion into knee extension?
L138-143 – You need to provide a reference to support your identification of that effect size, why do you think the f2 value will be 0.15? You should also provide more clarity on the test you plan to run as it is currently unclear, I get vastly larger expected effect sizes based on the values you have inputted here.
L202-203 – You may have changed the detail within the text, but you have not presented the 95%CI for the ICCs within Table 2.
L274-276 You have suggested you have removed NHE and NHC explanations. Why does it still remain? This lacks consistency and only adds confusion to the reader. This is poor academic practise.
L278 – Explain this in the text regarding the smartphone app. As it makes no sense to discuss it but not use it. Could remove and leave to a later paragraph.
L280 - A study is inanimate, it cannot investigate. This grammatically incorrect there is no issue with the context of the study.
L287 – I would suggest removing aspects of the volume, you shouldn’t adjust volume for the NHE and provide a consistent but maximal dose to ensure appropriate preparation. Adjustments in volume will likely lead to subsequent muscle soreness, while consistent maximal low doses appear superiorly effective.
Behan FP, Opar DA, Vermeulen R, Timmins RG, Whiteley R. The dose-response of pain throughout a Nordic hamstring exercise intervention. Scand J Med Sci Sports. 2023 Apr;33(4):542-546. doi: 10.1111/sms.14317. Epub 2023 Jan 19. PMID: 36651719.
Cadu JP, Goreau V, Lacourpaille L. A Very Low Volume of Nordic Hamstring Exercise Increases Maximal Eccentric Strength and Reduces Hamstring Injury Rate in Professional Soccer Players. J Sport Rehabil. 2022 Jul 13;31(8):1061-1066. doi: 10.1123/jsr.2021-0445. PMID: 35894913.
L295 – please see this meta-analysis on sprint and NHE
Bautista IJ, Vicente-Mampel J, Baraja-Vegas L, Segarra V, Martín F, Van Hooren B. The effects of the Nordic hamstring exercise on sprint performance and eccentric knee flexor strength: A systematic review and meta-analysis of intervention studies among team sport players. J Sci Med Sport. 2021 Sep;24(9):931-938. doi: 10.1016/j.jsams.2021.03.009. Epub 2021 Mar 22. PMID: 33893033.
L303 – Significance is off less relevance than the magnitude of the change or relationship. Please amend accordingly.
L335-336 – Are changes of 0.007 s or 0.015 s or 0.185 cm or 0.026 s practically relevant? No, these are much smaller than the associated error of the test.
L357 – It doesn’t matter if is significant or not, as you could have a significant trivial relationship purely based off sample size. You need to report the magnitude. Currently your correlations share between 16-44% of the expected variance, this is pretty minimal.
Table – Present the ICC 95% CIs.
Use points rather than commas when referring to further decimal places.
Dear authors,
Thank you for providing me with your revised version. I appreciate the work done. The authors have successfully improved the manuscript and changed it according to my suggestions.
nothing to add
nothing to add
nothing to add
Dear Authors,
The reviewers raised several questions, please revise the manuscript considering their suggestions/recommendations.
Thank you.
Best regards.
[# PeerJ Staff Note: It is PeerJ policy that additional references suggested during the peer-review process should *only* be included if the authors are in agreement that they are relevant and useful #]
1. Some sentences are long and complex, making comprehension difficult in certain areas.
Example: “Numerous studies have demonstrated that inadequate sleep and sleep deprivation can impair immune function, increasing susceptibility to infections, including the common cold.”
2. The research gap is not clearly defined. The introduction should state how this study differs from previous work.
3. The text should explain the key takeaways from figures more clearly. For instance, add a summary table for recommended sleep strategies before and after matches.
4. The study should emphasize its novelty. What is new in this review compared to existing sleep studies in sports?
5. If possible, include a flowchart showing how studies were selected, analyzed, and synthesized.
6. The description of sleep monitoring techniques (e.g., actigraphy vs. polysomnography) could be more detailed.
7. Some sections make generalized claims without citing specific studies.
Example of a weak claim:
“Proper sleep hygiene improves performance and reduces injury risk.”
Suggested Revision:
“Studies (xxxx) show that improving sleep hygiene reduces injury risk by X and enhances reaction time by Y.”
8. The impact of sleep on reaction time and injury risk is repeated in multiple sections. Merge these discussions into one well-structured section.
9. The manuscript mentions sleep-tracking devices but does not discuss potential inaccuracies.
9.1. Compare different sleep tracking methods and their reliability for athletes.
10. More Balanced Discussion. Contradictory research findings should be addressed. For instance, some studies suggest that sleep loss does not significantly impact skill-based performance—this should be acknowledged.
11. The conclusion should be more action-oriented. As a suggestion, for instance: “To maximize recovery and performance, clubs should integrate structured sleep interventions, including pre-match routines, sleep tracking, and circadian rhythm management.”
It requires substantial work with a lack on consistency and detail exploring topic. Further information is highlighted within the additional comments section.
The literature used could have gone further, with some missing key stone references but overall sufficient.
Professional table and figures presents.
No hypothesis is presented.
Appropriate study design with a defined research question, although there are a number of issues. The methods need further consideration and supporting.
Limited findings, no consideration of methodological considerations and its impact on the results. Additionally, you focus on the significant differences without taking into the context of the relevance to practise.
General comments
Thank you for the opportunity to review the manuscript, it is interesting and has some positive attributes, but it has some substantial flaws that require considerable work. You need to be consistent with terms and abbreviation throughout the manuscript.
Specific comments
Abstract
L34 – what do you mean by ball handling?
L35-36 – The nordic hamstring exercise and break point angle have no relevance or predictive ability for hamstring strain injury.
Green B, Bourne MN, van Dyk N, Pizzari T. Recalibrating the risk of hamstring strain injury (HSI): A 2020 systematic review and meta-analysis of risk factors for index and recurrent hamstring strain injury in sport. Br J Sports Med. 2020 Sep;54(18):1081-1088. doi: 10.1136/bjsports-2019-100983. Epub 2020 Apr 16. PMID: 32299793.
L40 – A study is inanimate, it cannot investigate.
L43 – What COD tests?
L47 – Any magnitude of relationship? Why run a regression? What if there is no correlation?
L51- Were they meaningful?
L54 – You have not assessed agility.
L55 – Hamstring strength was not assessed?
Introduction
L65 – reference required on enhancing player performance.
L67 – reference required on context of performance
L68 – Be consistent with terms, use either nordic hamstring exercise or nordic curl. This is an issue throughout the manuscript.
L69 – “eccentric exercise” Is it eccentric?
Ripley, N.; Fahey, J.; Comfort, P.; McMahon, J. Kinematic, Neuromuscular and Bicep Femoris In Vivo Mechanics during the Nordic Hamstring Exercise and Variations of the Nordic Hamstring Exercise. Muscles 2024, 3, 310-322. https://doi.org/10.3390/muscles3030027
Raiteri, B.J.; Beller, R.; Hahn, D. Biceps Femoris Long Head Muscle Fascicles Actively Lengthen During the Nordic Hamstring Exercise. Front. Sports Act. Living 2021, 3, 669813.
Van Hooren, B.; Vanwanseele, B.; van Rossom, S.; Teratsias, P.; Willems, P.; Drost, M.; Meijer, K. Muscle forces and fascicle behavior during three hamstring exercises. Scand. J. Med. Sci. Sports 2022, 32, 997–1012.
L72 – It is supra-maximal.
L80 – Again, be consistent with NHE or NHC not both.
L83-84 – Need further exploration of why nordic break point angle is important, i.e. relevance to eccentric hamstring strength.
Lee Li, C.; Yung, P.; Chan, K. The reliability and validity of a video-based method for assessing hamstring strength in football players. J. Exerc. Sci. Fit. 2017, 15, 18–21.
Sconce, E.; Jones, P.; Turner, E.; Comfort, P.; Graham-Smith, P. The validity of the nordic hamstring lower for a field-based assessment of eccentric hamstring strength. J. Sport Rehabil. 2015, 24, 13–20.
L89 – How can it directly affect performance?
L91- A study is inanimate and cannot aim
L95 – You need to provide a hypothesis
Materials and methods
L118 – What do you mean “uphold reliability”
L128 – Based on what study is your effect size based upon? Or why do you think it would be to that magnitude?
L138-149 – This can be condensed to a single sentence around exclusion of those with a previous injury.
L159 – You should highlight the limitation on calculating via flight time?
McMahon JJ, Jones PA, Comfort P. A Correction Equation for Jump Height Measured Using the Just Jump System. Int J Sports Physiol Perform. 2016 May;11(4):555-7. doi: 10.1123/ijspp.2015-0194. Epub 2015 Sep 21. PMID: 26390168.
L165 – Why use the best performance which discounts natural variability? What surface were the trials ran on?
L177 – Highlight it is 2D motion analysis
L178 – Did you use a tripod? Was it approximately or accurately at 3m?
L187 – Could use Kim (2013) as well.
Kim HY. Statistical notes for clinical researchers: assessing normal distribution (2) using skewness and kurtosis. Restor Dent Endod. 2013 Feb;38(1):52-4. doi: 10.5395/rde.2013.38.1.52. Epub 2013 Feb 26. PMID: 23495371; PMCID: PMC3591587.
L202-203 – The suggestions by Koo and Li are based on the 95% lower bound confidence intervals not the point estimate. Please change accordingly.
Results
L209-211 – This information is repeated from participant’s section.
L224 – You should present the correlations and linear regression here, currently missing the correlations.
Discussion
L262-263 – Why a decrease? I.e. inhibition.
L266 – Why did you not use the smart phone application?
L269-270 – Why assess in different phases of the season?
Opar DA, Timmins RG, Behan FP, Hickey JT, van Dyk N, Price K, Maniar N. Is Pre-season Eccentric Strength Testing During the Nordic Hamstring Exercise Associated with Future Hamstring Strain Injury? A Systematic Review and Meta-analysis. Sports Med. 2021 Sep;51(9):1935-1945. doi: 10.1007/s40279-021-01474-1. Epub 2021 Apr 29. Erratum in: Sports Med. 2021 Sep;51(9):1947. doi: 10.1007/s40279-021-01485-y. PMID: 33914283.
L271 – Intensity and volume? How and why would you manipulate these?
L272 – What do you mean by “player workload”?
L276 – What do you mean by adequate attention?
L278 – You have not assessed change of direction only manoeuvrability or change of direction ability.
L286 – You need to provide a reference related to change of direction performance.
L287 – Reference style
L289 – What about the magnitude?
L300-301 – What do you prior to high-speed running? Surely during?
Danielsson A, Horvath A, Senorski C, Alentorn-Geli E, Garrett WE, Cugat R, Samuelsson K, Hamrin Senorski E. The mechanism of hamstring injuries - a systematic review. BMC Musculoskelet Disord. 2020 Sep 29;21(1):641. doi: 10.1186/s12891-020-03658-8. PMID: 32993700; PMCID: PMC7526261.
L302 – What do you mean “functional demands”?
L305 – What do longer fascicles allow? Shortening velocity? Damage protection?
L311-312 – Is 0.007 seconds or 0.014 seconds meaningful or impactful for soccer players?
L316 – You have not assessed agility as this is a reaction to a stimulus.
L317-320 – You need to provide a reference for this description of the study.
L322 – intensity of contraction? What do you mean by this? Is it needed and how?
L329 – What protocol?
L331 – What do you mean by ranges of motion? Specific to the nordic hamstring exercise.
Conclusion
L334 – Meaningful?
L336-337 – Maybe significant, but not meaningful in practise.
L343 – What is the academic context?
Table 1. Use . not ,
Table 2 – How do the 95% confidence intervals not fall around the mean for 10,20,30m and CMJ?
Dear authors,
Thank you for the opportunity to review your manuscript. Although the manuscript is generally well-structured and follows standard scientific reporting formats, some minor and major concerns raised:
Major Concerns:
1. Sample Size Calculation (Lines 121-122): You correctly state the use of G*Power to perform an a priori sample size estimation. However, this calculation should be based on effect sizes derived from previous, similar studies. Please cite the specific study used as a reference for your calculation.
2. Informed Consent: In the line 136 you mention participants aged 16 to 18, but the eligibility criteria do not clarify whether informed consent was obtained from participants or their legal guardians. Given the mean age of 16.84 ± 0.61 years, it is critical not only for the participants to confirm but also that legal guardians provide consent, as this is an ethical requirement for minors. Your informed consent in the supplementary data lacks of this information.
3. Data Collection Instruments: In the data collection section, most outcomes lack information about the instruments used, except for KINOVEA with the NHCbpa. Identifying the measurement tools is important to understand their sensitivity and potential error margins.
4. Pearson Correlation Interpretation: The statistical analysis section lacks details on how Pearson correlation coefficients are interpreted. Consider adding a brief explanation, similar to how you described the interpretation of R-values.
5. Results Section (Lines 228-235): While the data are correct, the presentation could be clearer. I recommend listing the significant outcomes (p < 0.05) first, followed by a detailed analysis of each, prioritized by significance. Also, avoid redundant reporting, such as repeating the β value (e.g., “while a 1-unit increase in 20-m sprint time β = 24.166, p = 0.030) had an impact of 24.166 units…”). Please report this value only once.
6. Table Adjustments:
- Remove Table 5: This table appears redundant as its information overlaps with Table 4. Removing it would streamline the results.
- Add Pearson Correlation Table: Including a table that presents Pearson correlation coefficients would significantly enhance the clarity and depth of the statistical analysis.
Minor Concerns:
- Line 80: Define "NHC" upon its first mention.
- Line 81: Define "COD" upon its first mention.
no comment
no comment
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