Effects of Caffeine Supplementation on the Recovery of Professional Soccer Players

Round 1

Reviewer 1 Report

Dear Authors,

This study's objective was to evaluate caffeine supplementation's effects on soccer players during matches.  The main question of the research was whether caffeine supplementation could help soccer players recover and increase performance. The content and study design are relevant and exciting. It may need some originality because many articles on this topic are in other sports disciplines, such as endurance.  However, there needs to be more research where the actual circumstances, such as matches (soccer league), were analyzed. This is very interesting about this research.

I suggest only some minor changes. You mentioned a lot about soccer as a general sport and how popular it is. It does not make sense. I mean better explaining the importance of caffeine implementation in sports such as a game of soccer.

Why are the chapters Methods and Material at the end of your article.? It must be chapter 2 and then 3. Results, 4. Discussion…

The chapter discussion and conclusion are written very well. There are presented evidence and arguments according to the aim and the study results. Also, some limitations and possibilities of future research are presented.

Author Response

• The Introduction has been redone;
• The formatting of the article follows the journal's rules, therefore, the methods and materials are at the end of the article;

Author Response File: Author Response.pdf

Reviewer 2 Report

Thank you for the invitation to review this article. The topic is very interesting and it is always exciting to see field data in the practical setting. Unfortunately, the research design has several holes that are further exasperated by the writing style. These issues need to be further addressed. The study idea is very interesting but I'm not sure the authors designed a study that answers the question and bring novel information into the sports world. There are several interesting aspects to the design but it is lost due to some of the other, much larger holes and issues. 

General:

- Highly suggest the authors review the entire document for English-language grammar and style. There are: mixed tenses, confusing wording, and grammar mistakes throughout the entire document. Therefore, it is difficult to tell if there are holes in the design/research or if the issue is in the translation and presentation. Also highly suggest the authors review word choice and spelling using a US-based spell check.

- Introduction: the authors spend time discussing the popularity of the sport and the effect of caffeine on performance, however, the paper is focused on the effects of caffeine for recovery. Suggest the authors completely rewrite the introduction to reflect the purpose and primary variables of the study

- Methods: caffeine dosages should be listed as 183.085 as opposed to 183,083. Suggest the authors review the article for other mistakes similar to this one. The inclusion criteria needs clarification and objective criteria. It should also include an exclusion criteria (if any was used). This relates to the results where there was a large standard deviation related to minutes played. Was there a reason the caffeine dosages were chosen? No justification for these particular ranges was provided. 

Results: Figure numbers and descriptions do not match. Additionally, not all the figures contain figure descriptions. The  very first paragraph is very confusing. Rather than stating as supplementation vs consumption as part of a usual diet- a different representation of caffeine ingestion should be used.  Rather than percent differences, it may help to include raw values and which items were (or were not) statistically different. It may also help to differentiate if any of the differences held clinical or practical relevance. 

Discussion: does not seem to fully discuss the results in a dynamic and meaningful way. There does not seem to be much added to the literature. It is highly recommend that the results be reorganized and presented. From there, a more thorough and organized discussion be written. 

Author Response

• The review of the text in English was carried out by the company American Journal Experts according to the attached certificate
• The Introduction has been redone;
• The methodology has been rewritten for clarity.
• As for the inclusion criteria, the players who were in the matches were chosen, so there are no exclusion criteria;
• The amount of caffeine used was an average dosage of mg/kg of body mass

Author Response File: Author Response.pdf