Based in North Carolina, USA, Cognitive Buffer is a blog by Brian Downs. His posts reimagine ideas, discover hidden nuances, and analyze phenomena that may have not been obvious at first glance.

Use Your Head, Part 1

 

“If God had meant football to be played in the air, he would have put grass in the sky.”

-Brian Clough
 

 

After learning about the new NFL rule penalizing players for lowering their heads, I thought more about my favorite sport - soccer - and its risk for head injuries. Recently, US Soccer disallowed heading for youth players under age 12. The concussive risk of two players colliding in mid-air while going for the ball is measurable, but it is more difficult to quantify the impact of subconcussive trauma from heading the ball itself.

 

Soccer players commonly head the ball when it comes back into play after going out across the goal line (the short sides of the field that are adjacent to the goal). If the ball is out on the defensive team, the attacking team takes a corner kick from the corner arc where the goal line meets the touchline (the long side of the field). Often the player will put the ball in the air hoping that his/her teammate can head it in the goal. If the ball goes out and is last touched by the attacking team, the defensive team’s goalkeeper kicks the ball from within the 6-yard box - this is called a goal kick.

 

Goal kicks are often followed by first-touch headers, and the resulting scrum in the midfield has always seemed to me rarely productive. I became intrigued - does needless head trauma possibly occur just after goal kicks in soccer?

 

Goal kicks were introduced in 1869. In anecdotally reviewing older footage from years ago, balls appeared “heavier”, and goal kicks stayed close to or mostly on the ground. Legendary Argentinian goalkeeper Amadeo Carrizo revolutionized the position by using the goal kick as a means of counterattack.

 

The phenomenon of long passes in the air (but not specifically goal kicks) was examined by Chris Anderson and David Sally in The Numbers Game. Their data demonstrates that Premier League teams (top tier teams in England) who play possession-based football featuring short passes are more successful than teams who play a greater number of long passes (presumably more of which are in the air). So, if the long ball is generally less successful, why do goalkeepers play the long, airborne goal kick so much?  Are teams generally trying:

 

1.  To retain possession?

2.  To pin the opposition in their half?

3.  To clear the ball?

4.  To counterattack?

 

With these questions in mind, I collected data during the knockout round of the 2018 FIFA World Cup on June 30, 2018 and July 1, 2018. Specifically, I focused on goal kicks or free kicks taken by goalkeepers during which they played long balls in the air AND after which there were first-touch headers by either team. I excluded kicks if a player controlled the ball on the first touch with his chest or foot, or if a kick was taken short.

 

For the four games studied, the kicking team retained possession after 17 out of 39 kicks - a relatively low 44% of the time. In contrast, the kicking team retained possession 100% of the time when the kick was taken short (as they should have). When the chest or foot was used for first-touch control, the kicking team retained possession 5 out of 7 times (71%).

 

Of course, these numbers are small and this observational study is far from rigorously scientific.  I missed a few kicks because the TV cameras shifted to focus away from the action on the pitch. Also, some headers were hotly contested, and it was not clear who had hit it cleanly - so I did my best to make a determination. But it does appear that the kicking team is losing possession more than half of the time when there is a first-touch header after a goal kick.

 

If heading the ball after a goal kick is more likely to lead to loss of possession, why do goalkeepers still do this? Shouldn’t goalkeepers play goal kicks short or play it to field players who can control the ball with his chest or feet?

 

Some experts believe that frequent microtraumas to the head in American football contribute to neurodegenerative disease seen in the USA. Are there similar microtraumas in soccer, and do headers possibly contribute? How impactful is head trauma in soccer? I will explore this in an upcoming post.

 

 

 

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