January 2010

Out on a limb: Making a head case

Jordana Bieze Foster, editor

Athletes know about the importance of keeping your head in the game. Just ask Lindsey Jacobellis. Or Chris Webber. But a growing body of research suggests that poor decision making isn’t the only way the brain can sabotage an athlete’s performance.

A new study from the University of Ghent in Belgium, whose authors include leading authorities on the biomechanics of patellofemoral pain syndrome, used functional magnetic resonance imaging to demonstrate that wearing a brace or sleeve during knee flexion-extension exercises was associated with increased brain activity. This suggests that proprioception is more than just reflexive but actually involves a higher level of neural processing (see “Knee braces activate brain,” page 15).

The fMRI findings showed that what happens at the knee joint affects what happens in the brain. But what happens in the brain also affects what happens at the knee. And that may turn out to be a key issue for injury prevention.

Fatigue, for example, has been shown to affect biomechanics in ways that would predispose an athlete to injury. Intuitively, that effect would seem to be straightforward: Muscles get tired, so they aren’t able to function as well. Right?

Makes sense, but that may not be the whole story. But researchers from the University of Michigan have also found that exercising just one leg to the point of fatigue has an adverse effect on landing biomechanics in both legs. This suggests a central motor control mechanism is involved. And since an earlier Belgian study found that a knee sleeve can counteract the effect of fatigue on proprioception, it seems plausible that a common denominator exists somewhere between the ears.

All of this is even more interesting in light of a 2007 University of Delaware study which found that athletes who sustained anterior cruciate ligament injuries were more likely to have lower scores on a baseline neurocognitive test than those who were not injured.

Neurocognitive testing, of course, is best known in sports medicine for its role in managing concussion. Early research suggests concussion affects female athletes differently than male athletes. And we all know that gender is a risk factor in ACL injury. Coincidence? Maybe.

Increasingly, guidelines for return to play after a concussion include a requirement that athletes’ neurocognitive test scores return to baseline levels. The objective is to prevent “second impact syndrome,” which results when a second concussion occurs before the brain has healed from the first. But the Delaware findings suggest that this type of policy could also be protecting athletes from ACL injury—or other injuries of biomechanical origins, for that matter.

The realization that a given anatomical structure can be significantly affected by other proximal or distal structures has led to some of the most exciting work in sports medicine research to date. But to fully understand the mechanism of an injury—and how to prevent it—researchers may ultimately need to think outside the kinetic chain completely.

It’s not muscle, bone or joint. But the brain just might be sports medicine’s next frontier.

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