The Effects of Regional Muscle Strength and Mass on Standing Long Jump Performance
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe study is well conducted. However I miss the depiction of the results from the performance trials. As only correlation variables are present. Therefore in my humble opinion this would be needed to be considered for publication.
Further on the methods of the study should be placed right after the introduction as it's custom for articles such as this.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsI have no major criticisms, only one minor suggestions:
ADD TO THE PAPER ONLY TWO REFERENCES:
Gava P, Kern H, Carraro U. Age-associated power decline from running, jumping, and throwing male masters world records. Exp Aging Res. 2015;41(2):115-35. doi: 10.1080/0361073X.2015.1001648. PMID: 25724012.
Gava P, Ravara B. Master World Records show minor gender differences of performance decline with aging. Eur J Transl Myol. 2019 Aug 2;29(3):8327. doi: 10.4081/ejtm.2019.8327. eCollection 2019 Aug 2. PMID: 31579476
Author Response
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Reviewer 3 Report
Comments and Suggestions for AuthorsGeneral:
This study has a few unique aspects that make for interesting comparisons and findings.
However, there are a few major points to be clarified specifically in the statistical analysis.
The study has good potential, but must be improved before publication.
Title:
The title is alright, but I believe it could be more descriptive without being any longer. For example, the title could be changed to “The effects of regional muscle strength and size on long jump performance” or similar.
Abstract:
It is not particularly clear from the abstract if the regional strength and size measures are the ‘factors influencing standings long jump’. Can this be clarified?
The sentence “Multiple regression analysis revealed that…” is also a bit confusing and should be re-written for clarity. Can the authors clarify WHY trunk and upper limb strength were used in multiple regression?
Introduction:
I am not sure if the third sentence “This relationship is particularly evident when myofibrils are hypertrophic [3].” Is either accurate, or needed since the present study does not examine hypertrophy.
I also question the final sentence of the first paragraph. Indeed, there are discussions going on questioning the relationship between size and strength. (DOI: 10.1249/MSS.0000000000002662; DOI: 10.1249/MSS.0000000000002732). The present study is still interesting, but these sentences should be re-written/altered accordingly.
The rest of the introduction is well-written.
Methods:
Perhaps this is different for this journal, but typically methods come after the intro and before the results. Please check format requirements, although admittedly, I could be wrong.
For the power/sample size calculation, where did the effect size of 0.5 come from (This should come from a similar study)? Also, is this effect size Cohen’s d, or a correlation coefficient (Pearson’s r)? Please clarify.
Otherwise, the ‘participants’ section is well done and included the important and relevant information.
A unique method of evaluating trunk strength. Very interesting! Can the authors please include any reliability/variability statistics from other studies (even though I do see them reporting their own values below)? They do write “Maximum muscle strength can be demonstrated statically, with high reproducibility, and measurement is relatively easy [45]”. But should include the statistics (ICCs, CVs etc.).
Please include the sampling rates for the dynamometer
Can the authors explain why Pearson’s and Spearman’s correlations were used instead of just one?
Like the abstract, the methods should explain why some variables were put into the multiple regression instead of all/others.
The addition of confidence intervals would improve the reporting, and allow for a better interpretation of the spread of data.
Results:
The results show a Beta-coefficient symbol, but this symbol is not found in the ‘methods’ section. Please clarify. Is the Beta different than Pearson’s or Spearman’s?
The best reporting practices dictate that the significant simple correlations should be presented/illustrated in a scatter-plots so that the readers can see the relationships. A single, multi-panel figure would be great here.
If all correlations were significant (table 1), then why were only trunk strength and upper limb strength listed as factors that contribute to SLJ performance (table 2)?
Discussion:
The discussion is good but might change with the suggested revisions in the previous sections.
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
Comments and Suggestions for AuthorsThe manuscript from Nakai et al presents data aimed at determining the influence of trunk muscle strength, grip strength, and knee extension muscle strength assessed by quantitating jumping power.
With the current set of measurement data, the type of study represents a specific niche in muscle physiology and may be of interest to a very limited audience.
I strongly suggest the authors to increase the experimental setup, perhaps providing other measurements and further data to expand the applicability of their findings.
The very interesting data is nevertheless buried in the methods sections, whereas it may represent an important point to increase visibility and reference to the manuscript for other researchers wanting to measure similar parameters in different conditions.
While I appreciate that authors declare all limitations of their study, I still find the conclusions somewhat limiting the paper's visibility. Authors indeed say that: ‘The present study suggests that the performance of horizontal jumping ....should consider strength training of the trunk and upper limbs. This may provide insights into the design of training programs to improve performance in athletic activities that require a performance similar to that of the SLJ’
Such sentence in the discussion reduces the applicability of their findings to athletes with SLJ-like muscle training requirements. This is strongly impacting visibility of the manuscript.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Comments and Suggestions for AuthorsIf I am being picky, "95% confidence limits" can be reported as '95%CL'.
Otherwise, all edits are great, and the paper can be accepted now.
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
Comments and Suggestions for AuthorsNo comments to declare
Author Response
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