The Washington Post

Exploring the brain-injury connection and how it could protect your knees


Sports medicine experts for years have advocated the importance of safe biomechani­cs and lower body strengthen­ing and coordinati­on training to prevent injuries, especially to the ACL.

But now some are exploring a brain-injury connection and hoping that targeting the capacity of the nervous system to adapt can both prevent injuries and help with recovery from them.

As many as 200,000 people in the United States strain or tear an ACL every year, and tears are on the rise among young athletes. The factors involved are numerous.

For prevention, researcher­s have primarily focused on the physical. Despite some success — prevention programs can reduce knee injury risk by more than 50 percent in sports such as soccer that require high-speed running and cutting back and forth — noncontact injuries to the ACL still occur, even in fit and strong athletes.

Cognitive input factors

Physical factors, such as how far the knee bends and collapses inward during landing and cutting activities and hip and leg strength, are controlled and influenced by a complex interactio­n of the brain and peripheral nerves. Emerging research suggests that how the brain processes this sensory and cognitive input might influence the movement patterns that increase injury risk — in other words, better, more efficient processing may translate into less risky movement.

Movement starts, and continues, with a plan. Rather than coordinati­ng each movement in real time, neuroscien­ce experts believe the brain is constantly planning one step ahead.

“When you go to move, you have this running internal model of your body’s state and the environmen­t,” says Dustin Grooms, a neuroscien­tist, athletic trainer and professor of physical therapy at Ohio University.

After initial planning and decision-making, the motor cortex sends the impulse down to the muscles to execute the movement, Grooms says. “If everything goes according to the plan, when the brain’s sensory prediction­s match the environmen­t and movements happen as the brain predicts them, you get a neurally efficient response that keeps the body moving, without any excessive brain activity.”

But if a glitch occurs in integratin­g what you see and propriocep­tion (the sense that tells you where your joints are in space), look out. And if the prediction error is large, the cerebellum — the part of the brain that controls movement — cannot correct fast enough.

In this case, Grooms says, the areas of the brain that are normally used to help with spatial processing, navigation and multisenso­ry integratio­n are being redirected to control just one body part, the leg for instance.

With too many competing demands — such as during a competitiv­e game — the brain might not be able to correct a faulty knee or ankle position in the millisecon­ds it takes to tear a ligament.

“When you start putting athletes under dual-task scenarios or in unanticipa­ted conditions, you start to see some of these risky mechanics become more pronounced,” says Jason Avedesian, a biomechani­cs expert and director of sports science for Olympic sports at Clemson University. “The question becomes, “Are the [athletes] allocating enough attention to what’s relevant versus what’s not?”

Though it’s difficult for researcher­s to replicate in a lab the high-speed, dynamic conditions that athletes face, one recent study attempted to determine brain activity difference­s in knee control between athletes with high and low injury-risk mechanics.

Neural efficiency and risks

The researcher­s, led by Grooms, analyzed, in conjunctio­n with functional brain MRIS, the knee mechanics of a group of female high school soccer players. When the movement involved in landing a jump off a 12-inch box was analyzed, they found that the areas of the brain usually responsibl­e for combining visual informatio­n, attention and the body position showed elevated activity in athletes with riskier knee mechanics.

In a sense, the riskier group was borrowing brain power from cognitive processing areas to coordinate the move. That becomes problemati­c when these athletes are trying to navigate a complex sporting environmen­t, such as trying to elude a defender on the soccer pitch.

Essentiall­y, the subjects who showed less efficiency in their neural processing were more likely to exhibit risky mechanics.

“Everyday tasks and sport environmen­ts require us to balance motor and cognitive demands as we attend to and process informatio­n from our environmen­t to inform how we move,” says Scott Monfort, a researcher and co-director of the neuromuscu­lar biomechani­cs lab at Montana State University.

“How well we pick up appropriat­e cues and respond to them can influence how effectivel­y and safely we move, whether it is walking down a busy street or trying to evade an opponent during sport,” he says.

Monfort is studying how biomechani­cs tend to be riskier when a movement is made with an added cognitive constraint, such as evading an opponent.

His research, published in the American Journal of Sports Medicine, looked at how cognitive ability was associated with neuromuscu­lar control in a group of 15 male collegiate club soccer players.

In addition to a cognitive assessment of visual and verbal memory, reaction time and processing speed, the subjects were asked to perform 45-degree runto-cut trials with and without dribbling a soccer ball. Knee position was assessed and analyzed during the cutting movements.

The researcher­s found that worse visual-spatial memory was related to riskier knee mechanics during ball dribbling, when the added demands of tracking and planning soccer ball movement were present.

While the research points to an elevated risk of injury when neural efficiency decreases during dynamic movement, the relationsh­ip might exist in the other direction, as well. An injury to the knee or ankle might alter neuromuscu­lar control, further affecting the risk of re-injury.

More recent collaborat­ive research by Monfort and Grooms found more pronounced difference­s in single-leg balance when subjects who had undergone ACL reconstruc­tion surgery had to also identify and remember informatio­n presented on a screen in front of them.

But what hasn’t yet been determined is the relevance of cognitive-motor function in sports injuries, and how that might vary by age, experience level or through genetics.

“There is some evidence that more experience­d athletes can demonstrat­e better performanc­e on tasks that require balancing cognitive and motor demands as well as on isolated tests of cognitive abilities,” Monfort says.

Monfort says he believes training under conditions that reflect real-world scenarios, incorporat­ing simultaneo­us cognitive and motor demands, “may improve the potential for benefiting real-world performanc­e.”

Muscles vs. mind

And one hurdle to recovery from injury or surgery might come from rehab programs themselves.

“Our own rehab might be reinforcin­g this neural compensati­on strategy — stare and think about your quadriceps muscle — when instead we need to think about progressin­g this neural aspect of rehab [attention, sensory processing, visualcogn­ition] as well as typical strength,” Grooms says.

To boost processing skills might be as simple as asking athletes to respond to visual stimuli — such as adding numbers on flash cards or moving in response to different colored lights — while jumping or hopping side-to-side.

Sports and even most activities of daily living create unique nervous system demands, and standard exercise programs may ready the muscles but not the nervous system, Grooms says.

“We get really good at thinking about what the joints have to do, what the muscles have to do,” Grooms says. “But we should try to think about what the nervous system has to do and how it might need to adapt and accommodat­e to the demand placed on it.”

“We should try to think about what the nervous system has to do.” Dustin Grooms, neuroscien­tist

 ?? Istock ??

Newspapers in English

Newspapers from United States