Isometric Strength in Volleyball Players of Different Age: A Multidimensional Model
, Vladimir Grbić 1, Zoran Savić 3, Aleksandar Vićentijević 1, Zdravko Aničić 1, Marko Zadražnik 4, Lazar Toskić 3 and Goran Nešić 1Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
The study aims to define the age-related model of volleyball players multidimensional muscles’ contractile characteristics. The research question is interesting for applied sports scientists and practitioners. However, the manuscript has several limitations that need to be addressed. You mentioned the talent identification, and you use under 19 and under 21 years old players. The first two categories are acceptable. You have not included maturation effects in your model. Biological age is very important for studies like this. Also, what if you included the control group (not engaged in volleyball) that shows non-significant differences compared to volleyball players. Would it still be a model for prediction in volleyball? Are you using this statistical model based on one reference from the year 1979? Discriminant analysis or logistic regression is recommended in order to show if any of the variables can discriminate players according to gender and age. The main point is missing if those tests or abilities could differentiate volleyball athletes and show their importance.
Title
What is multidimensional in your study? You only measured isometric strength.
The title should be clearer and simplified.
Abstract
Line 12 this is the same sentence from the line 35-36. This first sentence in the abstract should be your introduction to the aim of the study.
Line 21 Is it possible for p to be <0.000
Line 19-23 If this is your main findings than the title should be age-related differences
Introduction
In general, the introduction lacks clarity and does not discuss the current state of the art research and gaps in the current research. Gaps not discussed are the relevance of isometric strength in volleyball.
- Materials and methods
Participants: The Peak height velocity or maturity offset is missing for the participants. This is of great importance for athletic development.
Testing procedures
When was testing conducted, part of the season?
Line 100-101 full specifications for instruments.
Line 113 You should describe warm up. Is it a standardized warm-up? What is a specific warm-up?
No familiarization with the protocols?
Were the subjects engaged in any activity 24-hour before performing the tests, which could be considered unduly fatiguing in regards to the strength testing?
The order of testing, rest between tests?
Who conducted the testing?
Line 116-118 This reference and sentence is not necessary. You should describe the testing and mentioned the instrument used. Moreover, is the instrument validated and what are the results (ICC, TE, CV)?
2.1.2 and 2.1.3 same as line 116-118 ICC, TE, CV
What are the results for all tests and how many repetitions?
Line 135 – are you sure that Figure 1 shows leg position which is similar to the squatting and pre-jumping positions?
Statistics:
Is there a correlation between tests?
To determine the variables that could differentiate the athletes, discriminant analysis or logistic regression are recommended. This is important if you want the determine the predictors that could discriminate the athletes according to level or age.
Results
No legends or units in tables
183-185 predictor for what?
Line 197 of 277N – 285N 368N - 415N?
Discussion
There is no comparison with some similar studies.
Line 192 p<0.000?
Line 225 So dimension reduction was only suggested in 1979 and now is 2020. I guess this is the only time it was suggested?
Line 264 p<0.000?
Line 271 speculate instead of hypothesizing
Conclusion
In conclusion, you only state what was found—no more discussion or speculation.
Additionally, you could write a practical application in the conclusion part.
Line 281-286: strength and limitation of the study in the discussion part.
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
General comments
It is extremely important to explore characteristic and essential muscle contractile profiles and potentials in a particular sport. The present study demonstrated that the “Score value” increased in age-dependent manner in junior volleyball players, but that the slope of its regression line was steeper in males than in females. The data could be of interest, but it should be noted that this study only showed changes in junior volleyball players' age-specific Scores, without comparable data for sedentary non-volleyball players or the athletes participated in other sports. Thus, this study is not the answer to the above proposition. There are several concerns that the authors should reply.
Major comments
- In lines 60-65, the authors hypothesized or assumed that the Score values, which determined by PCA analysis for the data of handgrip, lumbar, and ankle extensor isometric strength tests, may indicate general predictor of body movement and motoric potential. However, in order to establish this assuming, a comparison between volleyball players and sedentary or players participated in other sports should be required. For example, if this score shows performance and aptitude for volleyball, it seems that the top volleyball players should have a higher score compared with other athletes than volleyball. Or, although I can understand the present style of description, I think that it is better to devise the description on line 60 and beyond: it is possible to overcome the weakness above by re-reviewing the context of the introduction and/or the discussion part, thereby the manuscript being improved. In this sense, I think that a title is also overstated.
- Line 252-263: Can both the play styles and the pattern of training, which are depicted here, be generalized? Or, do the authors have an objective reference(s) or material(s) such as actual practice menu of the subjects participated in this study? More objective explanations or evidence are required. After all, I suppose that it can be solved if there is data for comparison between volleyball players and the others.
- Figure 1: No significant difference was observed in U17 and U19. I wonder if there is a meaning to draw a regression line.
Minor comments
- Introduction part: The first paragraph is a bit redundant. In my opinion, it is not necessary.
- Line 79-88: The data should be tabulated.
- Line 135, Fig. 1: This figure cannot be found.
- Line 152-154: It would be helpful if there was more explanation.
- Line 199-201: Is this difference due to the power/strength differences exerted depending on the angle? Is this true. More explanation should be given.
- Line 208-210: A reason remains unclear why the results for Fmax and RFDmax represent normative values of age-related maximal force and maximal explosiveness potentials.
- Line 236-238: This statement is clearly an overstatement.
- The manuscript would be improved by a thorough English language review.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The authors have extensively revised the manuscript based on the previous comments. The manuscript is much stronger. However, the lack of understanding of basic articles which are cited has me concerned that the conclusions drawn are lacking in rigour. Please try and refine what you are studying, what the characteristics of this sport are and what may contribute to its effectiveness.
I believe that you have worked hard on this study but it needs some changes to make it suitable for publication.
All the best.
Title
Unfortunately, the title now looks more confusing due to presenting model for age differences. We don’t need a model for age differences. Try to make it more like in the reference 30.
Or just a suggestion:
Isometric strength in volleyball players of different age: A multidimensional model;
Age related differences in isometric strength among volleyball players: A multidimensional model.
Try to make it more simple for readers.
Testing procedures
148-150 This references again didn’t presented clearly the exact procedures, because this is not gold standard instruments. Picture of the tests would give clearer picture of the procedures.
Moreover, you state that you have provided the validity and reliability. How was validity conducted?
Table 2 and 3
The legends are still missing
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
This version of manuscript has been a great improvement according the reviews’ comment. I have some advices.
Line 27-28: The authors concluded that the present data enable coaches to detect ones that stand out positively considering them as talented. I think that lack of data for non-volleyballers or poor players cannot allow this conclusion to be drawn as an abstract. As well, in lines 379-381, the auxiliary verb “can” is also a little strong as a conclusion of the present set of data. Of course, my opinion does not deny the usefulness of the data in this study, but it is necessary to devise the expression of the conclusion.
Line 278: The authors should replace “principal component analysis” with PCA.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
