Upper Extremity Kinematics and Electromyographic Activity in Uninjured Tennis Players

Round 1

Reviewer 1 Report

This paper presents the kinematics and electromyography (EMG) dataset of a group of ranked tennis players. The elbow, wrist, and forearm kinematics and EMG analysis are provided for both two-handed backhand and forehand.

I think the paper needs further analysis in kinematics. This current version is not sufficient enough. I have some following comments.

1. Why do the authors collect and analyze the joint angles and velocity. What do you think about the acceleration? In my opinion, the acceleration may impact the player and lead to injury.
2. Table 1, some joint kinematics have SD much bigger than its mean value, for example, wrist flexion/extension (10±20°).  Is it usually or not? Please provide some discussion or explanation about that.
3. Figure 2 and 4, How do the authors determine the muscle activation level (0-100%) from EMG signal? Please make it more clear.
4. Some small typo exists (mission degree symbol in Table 1). 

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

What a very interesting manuscript. Congratulations to the authors.

I feel every section is adequate. The introduction clearly states the problem, then an adequate methodology was applied, so that results could be discussed in line with the state-of-art.

 

Author Response

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Reviewer 3 Report

Although I like the idea of the study and believe it is needed. I do see a major problem with the design and interpretation of the results. The biggest concern is the sample size.

In the manuscript, the authors make a case for how normative data has been established with as little as 7 subjects in the other studies. So, 20 participants can be sufficient. However, with a low subject number, the group needs to be more homogenous. The data presented are for participants between the ages of 12-21. That is a period of development with rapid changes. 

There were subgroup comparisons but there were no details on how many subjects per subgroup and why only certain groups were chosen. For example, the age groups compared were 12-13 and 15-17, what about other age groups? If I had to make an educated guess, I would say there would be a difference between 21 year olds and 12 year olds. Was such a comparison made? Were there enough subjects to run that comparison?

Similarly, when comparing males vs females. Were the data for all males and females use in the comparison? There were 11 males and 9 females but how do they compare in terms of age and developmental stages? There are many reasons for why there were little difference between males and females. Were the females in the study older than the males? Could that have contributed to the findings? It should be at least addressed.

Based on the data presented, it is very difficult to reach the conclusions presented. With few subjects, any one subject can make a big difference. A step in the right direction would be to add an appendix with individual subject data. Another suggestion would be to do different studies with more homogenous groups.  As it stands, you can conclude that it is possible that different age groups, sex, and expertise could be similar but more extensive research would be needed to make that conclusion.

Author Response

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Round 2

Reviewer 3 Report

Thank you very much for your reply to my original comments. 

The addition to the methods section is good. However, the language used in the manuscript is still too strong. Specifically, on lines 270 and 282, it says "This study established a normative database". Compare that statement, to your response "the data represents a solid initial foundation of normative data". The language used in your response seems more appropriate and should be the language used in the manuscript. 

Author Response

Please see the attachment.

Author Response File: Author Response.docx