Physical Development Differences between Professional Soccer Players from Different Competitive Levels
, Andreas Ihle 3,4,5, Adilson Marques 6,7, Hugo Sarmento 8, Francisco Martins 1,2, Ricardo Henriques 9 and Élvio Rúbio Gouveia 1,2,3,*
Round 1
Reviewer 1 Report
I would like to express my gratitude regarding the opportunity to review this manuscript.
It is an interesting study, congratulations, but at this stage still requiring improvements. Below suggestions with line indication:
4-5 – Please insert space before each affiliation number.
6-20 – Please review the underline in the author´s emails (please observe journal guidelines).
35 – forward – The text format does not seem according to the journal´s template (for example paragraph size). Please confirm.
97 – Please include city and country.
97-98 - All tests performed in the same day? What was the difference in time regarding the first and last evaluation? Circadian effect?
105-109 – Seat or standing? Please describe in detail.
112-130 – Best repetition considered or mean? Please describe.
129-130 – Please describe the data collection conditions (place, space, temperature, humidity, and others).
134 – A validated box model? Please describe.
104-142 – Resting interval between repetitions should be described.
159 – Was statistical power test performed?
159 – Was players maturity determined? The M±SD between groups is different and may have influenced the results, therefore representing a study limitation (to be included in L 265-269).
References format should be carefully reviewed and corrected. They do not seem according to the journal instructions (size of letter and paragraphs, end points after journal, and others).
English should be carefully reviewed throughout the manuscript.
Author Response
Reviewer 1
1) I would like to express my gratitude regarding the opportunity to review this manuscript. It is an interesting study, congratulations, but at this stage still requiring improvements.
Response 1: The authors appreciate the reviewer's overall positive feedback.
2) 4-5 – Please insert space before each affiliation number.
Response 2: The reviewer's suggestion has been followed.
3) 6-20 – Please review the underline in the author´s emails (please observe journal guidelines).
Response 2: We appreciate your attention to detail. The correction has been made.
4) 35 – forward – The text format does not seem according to the journal´s template (for example paragraph size). Please confirm.
Response 4: The text is now according to the journal’s template.
5) 97 – Please include city and country.
Response 5: The information regarding the city and country has been added.
6) 97-98 - All tests performed in the same day? What was the difference in time regarding the first and last evaluation? Circadian effect?
Response 6: Each group of players (team) was assessed on the same day. The evaluation process of the four groups was performed on four consecutive days, one for each group. Each measurement in the Inbody platform occurs for approximately 20 seconds. The mean time between the first and the last evaluation was about 12 minutes. This information was added to the text as follows: “The assessment occurred in the early morning for four consecutive days in a laboratory. Each day corresponded to the evaluation of one single group. The mean time between the first and the last evaluation was about 12 minutes.” (line 105-108)
Unfortunately, the circadian effect was not considered in this study.
7) 105-109 – Seat or standing? Please describe in detail.
Response 7: The handgrip protocol was performed in a standing position. This detail was introduced in the text in the handgrip protocol description.
8) 112-130 – Best repetition considered or mean? Please describe.
Response 8: For both CMJ and SJ the best score was used for analysis. This information was added to the text after each protocol description.
9) 129-130 – Please describe the data collection conditions (place, space, temperature, humidity, and others).
Response 9: The body composition and balance assessments occurred in a laboratory during the morning. The lower-body explosive strength tests, the handgrip, and flexibility tests were performed in a gym facility of each club during the afternoon. Unfortunately, the temperature and humidity were not recorded.
10) 134 – A validated box model? Please describe.
Response 10: The sit and reach trunk flexibility box was used in this study. This is a validated box model printed in centimeters. This information was added to the text in the flexibility protocol description.
11) 104-142 – Resting interval between repetitions should be described.
Response 11: As suggested, the rest interval between repetitions was included in the protocol’s description.
12) 159 – Was statistical power test performed?
Response 12: We did not perform a power test. All players with full assessment were included in the analysis.
13) 159 – Was players maturity determined? The M±SD between groups is different and may have influenced the results, therefore representing a study limitation (to be included in L 265-269).
Response 13: Considering our participants' chronological age, we did not determine their maturity status. Following the reviewer's suggestion, we included this information as a study’s limitation (line 281).
14) References format should be carefully reviewed and corrected. They do not seem according to the journal instructions (size of letter and paragraphs, end points after journal, and others).
Response 14: We have performed an in-depth review in the format of the references according to the reviewer’s suggestion. We appreciate the reviewer's thorough revision.
15) English should be carefully reviewed throughout the manuscript.
Response 15: As pointed out by the reviewer, we did a thorough review in the English of the entire manuscript, which is highlighted in the text.
Reviewer 2 Report
Comments and suggestions for Authors
The topic of the present manuscript is interesting, and the results could increase the body of knowledge in this area. However, the experimental design shows some limitations that should be addressed in the manuscript and the results should be generalized with caution.
First, fundamental components of the soccer performance have not been considered in the assessment of the soccer players (i.e. speed, endurance). For example, the Authors report that explosive strength (SJ and CMJ) is highly correlated with short sprint performance (30 m) but these short phases of acceleration (15-30 m) could be assessed and included in the present cross-sectional study. Also, the repeated sprint ability and aerobic endurance (i.e. VO2max) are completely ignored. The Authors should explain the reasons in the limitations section at the end of discussion.
Second, rationale and specific hypothesis of the study should be better explained at the end of the introduction section. For example, the Authors included grip strength measurements in the material and method, but they did not report in the introduction section the reasons why these variables were assessed.
Third, material and method section should be more detailed (i.e. it has not been specified the sequence of the measurements and were the measurement were conducted, number of jumps, etc.).
Forth, the Authors should underline the novelty of their investigation in the introduction and discussion sections.
Minor points:
The Authors should consider to change the term “Physical Fitness” with a more appropriate term in the performance analysis of soccer players (in the model of Ford et al., 2011-rif1 it is not reported this term).
Line 103. Please, use hand grip strength in place of static strength.
Line 118. Please, remove “tall”.
Line 119. Please, change the term “dropped into” with “executed a counter movement”.
Line 127. “Researchers’ count of three before jumping” Please, include a specific reference.
Line 265. Why the “sample size” is a limit? Post-hoc analysis was performed? Please, explain it.
Line 272. Please, remove “sports agents”.
Line 273. “Specific strength content” are already included! Please, change the sentence underlying the novelty of your results.
Lines 277-287. This part does not appear as a conclusion.
Author Response
Reviewer 2
The topic of the present manuscript is interesting, and the results could increase the body of knowledge in this area. However, the experimental design shows some limitations that should be addressed in the manuscript and the results should be generalized with caution.
First, fundamental components of the soccer performance have not been considered in the assessment of the soccer players (i.e. speed, endurance). For example, the Authors report that explosive strength (SJ and CMJ) is highly correlated with short sprint performance (30 m) but these short phases of acceleration (15-30 m) could be assessed and included in the present cross-sectional study. Also, the repeated sprint ability and aerobic endurance (i.e. VO2max) are completely ignored. The Authors should explain the reasons in the limitations section at the end of discussion.
Response 1) We agree with the reviewer on these points. Indeed, we collected the data concerning speed (10-, 20-, and 30 m linear sprints), agility (t-test), and aerobic and anaerobic endurance (Yo-Yo Intermittent Recovery Test). However, those tests were performed in each team stadium, and the fields differed in natural and artificial grass. Therefore, we did not feel comfortable using those data to make comparisons between groups. This limitation has been added in the limitations section as suggested (line 282-283).
2) Second, rationale and specific hypothesis of the study should be better explained at the end of the introduction section. For example, the Authors included grip strength measurements in the material and method, but they did not report in the introduction section the reasons why these variables were assessed.
Response 2) As suggested by the reviewer, information including grip strength and the specific hypothesis of the study was updated in the introduction section as follows: “Meanwhile, strength has been consistently evaluated worldwide in sports, being pointed out as a significant predictor of performance. Among testing protocols, the handgrip emerges as an attribute of elite athletes and a covariate of overall strength [8].” (line 51-53)
“Therefore, to close these important gaps, the purpose of this study was to assess and compare in detail the body composition, strength, and balance parameters of elite and non-elite professional soccer players. It was hypothesized that elite players present superior performance in all variables assessed compared to their non-elite peers.” (line 76-80)
3) Third, material and method section should be more detailed (i.e. it has not been specified the sequence of the measurements and were the measurement were conducted, number of jumps, etc.).
Response 3) The protocols used for each assessment are now described in more detail in the Materials and Methods section.
4) Forth, the Authors should underline the novelty of their investigation in the introduction and discussion sections.
Response 4) The authors appreciate the reviewer suggestion and have now updated the introduction and discussion sections.
5) Minor points: The Authors should consider to change the term “Physical Fitness” with a more appropriate term in the performance analysis of soccer players (in the model of Ford et al., 2011-rif1 it is not reported this term).
Line 103. Please, use hand grip strength in place of static strength.
Line 118. Please, remove “tall”.
Line 119. Please, change the term “dropped into” with “executed a counter movement”.
Line 127. “Researchers’ count of three before jumping” Please, include a specific reference.
Line 272. Please, remove “sports agents”.
Line 273. “Specific strength content” are already included! Please, change the sentence underlying the novelty of your results.
Lines 277-287. This part does not appear as a conclusion.
Response 5: The authors have performed the revision of the manuscript following the reviewer’s minor suggestions.
6) Line 265. Why the “sample size” is a limit? Post-hoc analysis was performed? Please, explain it.
Response 6: The authors have considered the sample size limit since the number of individuals in each group varied between 17 and 22. We believe that a greater number in each group would allow a better representation of each population.
Round 2
Reviewer 1 Report
Dear authors,
Thank you for considering my suggestions and incorporating them into the manuscript. Below some more small suggestions regarding details, with line indication.
L7 – Please correct “.com_”.
L29 – “CA” first appearance in the abstract should be in full.
L299-301 – “On the other hand, body composition variables did not differ substantially between groups. The lower-body explosive strength was the main discriminator between players in several competitive levels, with elite players outstanding significantly than their non-elite peers.” – Please review the English in these lines and throughout the manuscript (one calm and final reading is suggested).
L314 – Please insert spaces between “Author Contributions”, “funding” and all the others (according to journal template).
L324 - “Institutional Review Board Statement” – Should be presented in bold.
326 – “of Human Kinetics” – Please confirm if no more than one space.
Please carefully review all the references according to journal instructions for authors. For example, ref 23 journal format is not correct.
Congratulations for the research and keep up the good work.
Author Response
Reviewer 1
Dear authors,
Thank you for considering my suggestions and incorporating them into the manuscript. Below some more small suggestions regarding details, with line indication.
L7 – Please correct “.com_”.
L29 – “CA” first appearance in the abstract should be in full.
L299-301 – “On the other hand, body composition variables did not differ substantially between groups. The lower-body explosive strength was the main discriminator between players in several competitive levels, with elite players outstanding significantly than their non-elite peers.” – Please review the English in these lines and throughout the manuscript (one calm and final reading is suggested).
L314 – Please insert spaces between “Author Contributions”, “funding” and all the others (according to journal template).
L324 - “Institutional Review Board Statement” – Should be presented in bold.
326 – “of Human Kinetics” – Please confirm if no more than one space.
Please carefully review all the references according to journal instructions for authors. For example, ref 23 journal format is not correct.
Congratulations for the research, and keep up the good work
Response: The authors thank reviewer 1 for the overall positive feedback and the thorough review. We have now addressed the minor suggestions and performed an in-depth English review. We hope the manuscript is suitable for publication.
Reviewer 2 Report
Comments and suggestions for Authors
The manuscript has been improved following the suggestions of the present reviewer. However, minor points should be addressed before its acceptance.
Line 30 and 287. Please, change the term “sports agents” with a more appropriate term.
Line 129. What does “gym facility” mean? Please, use appropriate term that are used in the scientific literature.
Lines 130-140. How many trials in SJ and CMJ were performed by each participants? Please, include in the text.
Line 103 and Table 1. Please, change height in stature.
Discussion section. Please, discuss the difference in relative terms (%).
Line 280. The Authors cannot state that the sample size is small without performing a Post-hoc analysis or reporting references of similar studies. A post-hoc analysis can be executed with G-power or other free software easily.
Author Response
Reviewer 2
- The manuscript has been improved following the suggestions of the present reviewer. However, minor points should be addressed before its acceptance.
Response 1: We appreciate the reviewer’s overall positive feedback.
- Line 30 and 287. Please, change the term “sports agents” with a more appropriate term.
Response 2: The term “sports agents” was changed to “sports staff”.
- Line 129. What does “gym facility” mean? Please, use appropriate term that are used in the scientific literature.
Response 3: By “gym facility” we were referring to a space equipped with several physical performance assessment tools. As suggested by the reviewer, we have changed the term “gym facility” to “physical performance laboratory”.
- Lines 130-140. How many trials in SJ and CMJ were performed by each participants? Please, include in the text.
Response 4: The total number of trials performed by each participant was included in the text as follows: “In total, each participant performed seven trials in each jumping assessment.” (line 130-131)
- Line 103 and Table 1. Please, change height in stature.
Response 5: We have followed the reviewer's suggestion and changed “height” to “stature”.
- Discussion section. Please, discuss the difference in relative terms (%).
Response 6: As suggested by the reviewer, we added the difference in relative terms in the Discussion.
- Line 280. The Authors cannot state that the sample size is small without performing a Post-hoc analysis or reporting references of similar studies. A post-hoc analysis can be executed with G-power or other free software easily.
Response 7: The authors have followed the reviewer's suggestion and removed the statement referring to the small sample size.
