A recent study published in the journal Interface adds to the growing body of evidence that it does not require a clinical concussion for hits to the head to cause lasting damage in the brain.
Most research on the effect of brain injuries has focused on the impact of relatively big hits which cause clinically diagnosable brain injuries, but new research from Stanford University examined the impact of smaller “sub-concussive” hits of the brain against the inside of the skull, finding even tiny injuries can have huge effects on the brain.
For the study, the researchers used MRI data from the brains of three patients to assess exactly how much the brain was able to move inside the skull, and in which directions. The intent was to determine the frequency at which the brain bounces around inside the skull, measured at cycles per second, or hertz.
Using the data collected from the MRIs to create a statistical model, the researchers found that the brain can be damaged when the brain oscillates at a rate of 15 hertz. For comparison, turning your head when a person walks into a room or glancing at your phone is associated with a rate of 5 hertz, but contact sports are known to push the brain to 20 hertz.
While concussive injuries are caused by a single impact which causes the brain to bounce off the skull, the researchers found the continuous little bumps sustained during a regular football game are likely to cause just as much damage as a single concussive impact, even when players are wearing helmets.
The researchers hope the findings lead to improved helmet designs which will minimize the amount of movement of the brain inside the skull, but until such innovations occur the results paint a grim picture for contact sports and the brain health of athletes.