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