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Can tackling harm your brain?

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When former England striker Jeff Astle died from early onset dementia in 2002, the coroner put it down to heading footballs. Since then, several studies have linked repeated head trauma with degenerative brain disease, prompting Dr Andrew Lavender to investigate whether minor trauma from tackling could also affect a player’s brain function.

Rugby player running to end of field and getting tackled by another player.

For athletes playing contact sports, head and body clashes are common. Pounding knocks, jarring collisions and swift changes in direction can cause the brain to bounce against the skull resulting in microscopic brain trauma, sometimes on both sides of the brain’s outer surface.

“Although the brain is encased in a protective skull and cushioned by fluid, a sudden change in direction can cause the nearside to impact the skull, then rock back so the other side is also impacted – a coup-contrecoup effect,” Dr Lavender explains.

While concussive injuries stemming from head blows are well documented, it is lesser known that brain injuries can also occur without head contact, for example when a player’s body suddenly changes direction, causing a whiplash movement to their neck.

“In a rugby tackle players cannon into each other, but if at the last split second the player tries to dodge, the impact is not at the precise moment or the precise position the player is expecting, they may move differently and that changes the impact.”

Dr Lavender’s current study examines the incidence of brain injuries so minute they don’t appear to have an immediate effect, but could have more serious effects in the longer term.

“A player may feel just fine after a tackle but what has actually happened to their brain? Has it been jostled around enough to cause a minor injury?”

Using techniques that assess the brain’s cortical neural pathways, Dr Lavender meticulously looks for evidence of microscopic brain changes following a tackle, which are not detectable by sideline tests or even the player’s own perception.

“They are not classified as injuries at this point. In fact, the players themselves probably won’t notice any difference. But when we run neurological tests, we can detect a difference.”

To gather data, he simulates tackling events in a motion analysis laboratory, so far testing male and female rugby players.

“In each simulation we have two players, one at either end of the mats, timing gates at either end – so we can set their speed as they are coming in – and they go through a tackle.

“It’s not a full tackle, like in a game. But they are hitting each other at a similar speed to what is typical in a game and the technique is there. It is sufficient to see if there is any movement of the head relative to the torso.”

During the simulations, players wear markers on their shoulders and head, which are tracked by motion analysis software – the same technology used to create avatars.

“The software provides data that tells us how much the head is moving relative to the shoulders at a particular point in time. And from that we can infer how much the brain is moving inside the skull,” Dr Lavender explains.

Preliminary data shows that rugby players’ heads don’t actually move that much in relation to their bodies, an observation Dr Lavender ascribes to their experience in the sport.

“Rugby players know how to tackle well. Their neck and shoulders are controlled. They roll their body into the right angle, use their shoulders and tense up at just the right time and brace in the right kind of way.

“What becomes a problem for them is when there is something slightly different or they get hit from an angle they are not expecting, or they lunge at an opponent’s hips and get hit in the face with a knee and that causes the head to move about differently.”

Following the simulations, Dr Lavender conducts tests on a player’s memory and balance, as well as a cortical inhibition test, where the brain is briefly stimulated with a magnet to measure signals from the brain to the muscles.

“The study has found an increase in activity of the brain’s inhibitory neural pathways – a reflection of protective mechanisms against minor injury – but unless you do an in-depth assessment, you can’t tell.

“A player can probably walk and function basically fine, but there is a change in the way their brain is operating. This change is imperceptible to the player and normalises within 24 hours.”

Dr Lavender will be gathering data for another year, but he is keen to stress his results are unlikely to warrant changing the ways in which sports are practised and played.

“A reasonable take-home message is that tackling may cause some short-term effects but the brain recovers quickly. We don’t see anything that is debilitating in the long-term at this stage. This is different from players who have experienced multiple concussions across an entire career.

“Scientists have examined the brains of players who died from dementia and found severe damage to their brains as a result of a long sporting career with many concussion injuries.

“If you did the same with players who had not suffered multiple concussions when they eventually died, we expect you would see a pretty healthy brain.”

See more at Curtin Open Day!

Take a tour of the exercise science and physio labs on Open Day, 29 July 2018.

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