Heads Up! A Biomechanical Pilot Investigation of Soccer Heading Using Instrumented Mouthguards (iMGs)

Round 1

Reviewer 1 Report

This article is an important contribution to a growing concern in the sport (at the professional and amateur levels).  It could lead to a proactive approach to mitigating the potential short- and long-term effects associated with repetitive HAE sustained by soccer players. Such biomechanical with head kinematics studies are needed to quantify the magnitude and frequency of HAE sustained in training and game exposures.

But I have identified a few items I would recommend to further target the boundaries of the studies and translate them into material clarification and potential recommendations or future development.

First, in section 2.1[Lines 136-140] other avenues might have been used (or discussed later on) in the methodology and data acquisition. Can you briefly explain the reasons behind the choice? For example, why haven’t you considered the Head Impact Telemetry severity profile [HITsp]), or the HAE load sustained by players during the instrumented session would it be giving complementary information? You might have good reasons that would benefit the readers’ knowledge and help to better characterize the choices.

Second, in the results [Lines 162-166], a simple table would help clarify the results by giving an overview rather than a written list of data.  These results are significant and would benefit from the structure of a table.

Third, in the Discussion section, you use many references to studies involving women’s cohorts [for example, Lines 187-190 or 234-239]. Notably, some studies found that Mean impact magnitudes were significantly greater for females for PLA, while mean PAA was greater for males. To better set the frame of the study, it would be pertinent to highlight the potential differences related to genders associated with the measures in your study. 

Fourth, whilst most existing research and studies are from other contact sports such as American Football, hockey, or rugby populations, risk concerns associated with soccer are growing, but more studies like this one are needed. Until more is understood about the differences in concussion rates and HAE exposure rates between soccer players and players of other contact sports, it would be useful to help the reader identify what differentiates the characteristics of soccer-related HAE from other sports.

Finally, in the conclusions, it would improve the “material” impact of the last portion if some examples of future mitigation strategies (opening for more research or recommendations), from the authors’ perspectives, could be identified. For example, the characteristics of high-risk scenarios could be identified and used to inform strategies to reduce the number HAE sustained in training and game exposures. It looks like the last sentence fall short in not opening well the next steps as seen by the authors.  It’s an important topic, more studies are needed, and some orientation or recommendations would surely be welcomed by the readers.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

This study attempts to identify and quantify head kinematics associated with different types of on-field header impacts in men’s collegiate soccer. The paper is fairly well written and provides some good insights on this topic. It would be useful to report the percentage of players that used the mouthguards in games and what the results represent in terms of exposure. So how many matches and players are the results really based on? Is it possible that the results are biased based on only a small number of players wearing the iMG and therefore the results are not reliable?

Please see further comments below:

Line 14: delete the extra closing bracket.

Lines 23-24: Are there any practical applications that can be added from the study findings?

Line 47: Please provide some details about the specific types of head incidents reported.

Line 67: Delete “events” after “HAE”

Lines 105-106: Change CI values to two decimal places.

Line 200: Please be more specific about what is meant by “contact practices”.

Lines 241-243: This sentence should be more clearly described to assist readers with their understanding.

Line 266: Define “CG”

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

Dear Authors,

thank you very much for sending the article titled: Heads up! A biomechanical investigation of soccer heading using instrumented mouthguards (iMG) for the review process. The article seems interesting, but the authors should correct it according below suggestions:

- please include a flowchart at the beginning of the materials and methods section

- lack of inclusion and exclusion criteria of experiment participants

- IMU sensors are recently used for collecting data from sports. For example in the article titled: Body Parts Accelerations evaluation for Chosen Techniques in Martial Arts authors analyze accelerations in Judo. To improve article quality please cite above manusrtipt and write a few sentences about the use of sensors in sports.

- Figure 2-3. Please include a p-values

- lack of future study

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Well done on adequately addressing my concerns and improving the quality of your manuscript.