June 13, 2007 / 4:38 PM / 13 years ago

Slow brain function linked with solo knee injuries

NEW YORK (Reuters Health) - In a new study, researchers found measurable decrements in the brain function of intercollegiate athletes who sustained anterior cruciate ligament (ACL) injuries that were not associated with a collision with another athlete or object.

“The results suggest that slower processing speed and reaction time, as well as lower visual and verbal memory performance, may predispose a person to errors in coordination during physical activity that can lead to injury,” Dr. Charles Buz Swanik from University of Delaware in Newark told Reuters Health.

“A torn ACL is frequently involved when a person explains that they “blew out their knee,” Swanik noted. “There is an audible ‘pop’ and the knee becomes unstable, often buckling or giving way simply during walking.” Non-contact ACL injuries don’t involve other players or objects, “hence the person, in a very literal sense, caused the injury themselves,” he explained.

“This can happen because during physical activity, knee joint forces can exceed six-times one’s body weight, but muscles actually provide most of the stability to joints. In fact, so much of the support comes from muscles (that if) the proper muscles are not contracted at the right time, too much load is exerted on the ligaments causing a tear.”

Swanik and his colleagues designed their study to determine whether athletes who experienced a noncontact ACL injury had a decrease in preseason in mental performance compared with athletes without this injury (the “controls”).

The researchers matched 80 intercollegiate athletes who, after neurological and cognitive testing, suffered a noncontact knee injury, with 80 uninjured controls.

There were statistically significant differences between the two groups on all four neurocognitive tests, the team reports in the American Journal of Sports Medicine.

Compared with the uninjured control subjects, the athletes with knee injuries had a significantly slower reaction time, processing speed and performed worse on visual and verbal memory.

Much of the previous research on mechanisms involved in noncontact knee injury has focused on measuring muscle activity and limb alignment, Swanik noted. However, noncontact knee injuries “are the result of the person’s choice in a movement strategy, which occurs in the brain. This coordination of muscle contractions requires a great deal of advanced mental preparation — thinking ahead to anticipate events — but also a capacity to react to the unexpected,” Swanik said.

Minor deficits in mental processes “may cause spatial disorientation or loss of situational awareness that disrupts the coordinated muscle contractions needed for joint protection,” he added.

Swanik believes more research is needed to focus on the link between mental skills, coordination and injury proneness. The testing of athletes’ mental skills may have a role in injury prevention, he said.

SOURCE: American Journal of Sports Medicine, June, 2007.

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