Differences in External and Internal Load in Elite Youth Soccer Players within Different Match Timing Zones

Round 1

Reviewer 1 Report

The manuscript titled "Differences in External and Internal Load in Elite Youth Soccer Players within Different Match Timing Zones" analyzes the internal and external load of elite youth soccer players as a function of playing time. The conclusions regarding the influence of elapsed time are supported by the statistical analysis performed.

Although this paper appears to be well written and the conclusions are supported by the results, there are several errors. Most of the errors and inconsistencies concern the units of measurement:

1. What is the [n.m^-1]? Newton per meter? Why is this a unit of measurement for acceleration?
2. The unit of measurement for acceleration and deceleration is not [m.s^-1], but [m.s^-2].

These two comments should be corrected throughout the paper.

3.Subsection 2.2 should be deleted; the first two sentences logically belong to the previous subsection, "Subjects", and the section on ethical standards and ethics committee approval should be included in the designated section at the end of the manuscript.
4.Regarding the results in Table 1, if the hypothesis is rejected (as in Z6), no a posteriori analysis should be performed.
5.There is a significant difference in DCCz2 for different time zones, but according to post-hoc analysis, there is no significant difference; it could be possible, but please check if the results of statistical analysis are correct.
6. The header of Table 1 should not be on a separate page.

Some minor errors:
7. ln 26 - the standard deviation is missing. 
8. ln 28 - there is a point after vs.
9. ln 136 - unit of measure for Savg is missing.
10. ln 140-143 - several errors in the use of [m.s^-1] for acceleration and deceleration.
11. ln 169-170 - several errors related to the use of [n.min^-1] for acceleration  and deceleration.
12. ln 172 - 42 appears to be too large of a standard deviation, please check if this is a typographical error or an error in the data collected.
13. ln 179-10 - several errors related to the use of [n.min^-1] for acceleration and deceleration.
14. Table 1 - use of [n.min^-1] for acceleration and deceleration in the table body and [m.s^-1] in the caption.
15. Table 1 - use of [m.min^-1] for covered distances in each speed zone in the body of the table and [km.h^-1] in the caption.
16. ln 271 - standard deviation missing.
17. ln 273 - missing data for HIR.
18. ln 281-283 - what are ACC.min^-1 and DCC.min^-1?
19. ln 284-286 - several errors in using [n.min^-1] for acceleration and deceleration.
20. ln 303-304 - this sentence should be rewritten.

Author Response

Dear reviewer,

 

thank you very much for very stimulating and helpful comments. We realized that the submitted work can be improved based on the assessment and incorporation of comments. We appreciate your time and effort in order to provide your revision with aim to improve the submitted manuscript. We believe that the new version has a higher quality and would be interesting for readers. We believe that the published research issue will find a large circle of readers and will also be cited in another studies. Once again, we would like to sincerely thank you for your time, effort, professional and factual comments.

Have a look attached file with corrections and justification which has been made please.

Authors.

Author Response File: Author Response.pdf

Reviewer 2 Report

First, I thank the editors for the opportunity to review this study. In this study, the authors analyze the internal and external load during one match in 66 elite youth soccer players. Despite the original work done by the authors, my opinion is that the work cannot be evaluated in this form. Modifications are needed before it can proceed.

 

The authors in general did a decent job however some critical issues make the work incomplete and unclear.

 

1) in the methods section it is necessary to clarify how all the variables described were obtained (example: high-metabolic load distance) or cite studies that have previously described them. 

2) the analysis of so many variables needs a more detailed presentation of the results.

3) make a graph for distance 

4) make a graph for high-metabolic load distance

5) realize a table for the Zones 

6) realize a table for accelerations

7) realize a table for decelerations 

 

8) post hoc analysis should be limited to fewer variables

 

in general I recommend that the authors revise the design and reduce the number of variables to reduce confounding factors.

Author Response

Dear reviewer,

 

thank you very much for your review. We realized that the submitted work can be improved based on the assessment and incorporation of some comments. Also, we would like some comment better clarify for readers. We appreciate your time and effort in order to provide your revision with aim to improve the submitted manuscript. We believe that the new version has a better quality and would be interesting for readers. Once again, we would like to sincerely thank you for your time, effort, professional and factual comments.

Have a look attached file with corrections and justification which has been made.

Authors.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

 

Thank you for the answers and the clarification. The corrections made are satisfactory and the paper is now in a form suitable for publication.