Suzuki K, Nagai S, Iwai K, Furukawa T, Takemura M. How does the situation before a tackle influence a tackler’s head placement in rugby union?: application of the decision tree analysis. 

The full paper can be found here.

Keita Suzuki


Tell us more about yourself and the author team.

My research focuses on injury prevention in rugby union. In particular, I conduct epidemiological surveys and use video analyses to prevent concussion and neck injuries. I am a retired rugby player, but I have played for 18 years. As a team medical staff member, I have also supported collegiate rugby union players with their rehabilitation. I am currently involved with a high school rugby team as an S&C coach and a medical staff member. Our team of authors also all have experience playing rugby or supporting players as coaching or medical staff.


What is the story behind your study?

In rugby union, concussions occur most frequently during tackling. Video analysis of players at various playing levels involved in concussion incidents shows that the incorrect placement of the tackler’s head is a risk factor for concussion. However, as per the answers we received, when interviewing the players, we found that they would still attempt to make the tackle, even when the head placement was incorrect if the ball carrier might break the gain line. Even if the players are aware that incorrect head placement can be a risk of concussion, avoiding actions leading to concussion can become less of a priority than team performance, especially during a match. Therefore, we needed to identify the situations where players tackle incorrect head placement to prevent concussions. This was achieved by using machine learning.


In your own words, what did you find?

We found three situations that were likely to result in incorrect head placement. The characteristic that most influenced the tackler’s head placement was the evasive manoeuvre of the ball-carrier. Our results suggest that it is essential to use the appropriate technique to adapt to the movement of the ball carrier. Based on the factors related to the three situations analysed, we focused on tackler behaviours to prevent incorrect head placement: the tackler controls his speed and raises his head, allowing him to check the ball carrier’s movement and decide on the appropriate head position.


What was the main challenge you faced in your study?

Rugby union is a collision sport, and injuries, including concussions, occur more frequently than in other sports. In Japan, the number of young athletes has increased in the wake of the 2015 and 2019 Rugby World Cups. Therefore, it is important to provide a safe environment for rugby. Recently, video analyses have increasingly been used to examine tackler-related concussions in rugby union to reveal the characteristics of these concussions.  However, previous studies only identified isolated characteristics. Our research used a decision tree analysis, a machine learning technique that has recently been used in sports science, to show, in sequential order, the multiple features that lead to tackles with incorrect head placement. Using this method, we believe players and coaches would easily understand what actions they could take to avoid the risk of concussion.


If there is one take-home message from your study, what would that be?

Players who frequently tackle with incorrect head placement may have problems during the approach phase. Therefore, we believe it is important to review matches and team training footage to correct these problems to prevent future concussions.

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