High school football players who experience repeated hits to the head show changes in mental processes even when there are no clinical signs of concussion.
Data from sensor-equipped football helmets could help efforts to develop more effective safety guidelines based on the maximum number of hits a football player should receive, says Eric Nauman, associate professor of mechanical engineering at Purdue University and an expert in the central nervous system and musculoskeletal trauma.
The findings may also help develop techniques for coaches and players to reduce the severity of blows to the head.
A two-year study of high school football players compared helmet-sensor impact data from each player with brain-imaging scans and cognitive tests performed before, during, and after each season. Video of each play showed how athletes sustained impacts.
The researchers evaluated players using functional magnetic resonance imaging, or fMRI, along with a computer-based neurocognitive screening test. The fMRI scans show which parts of the brain are most active during specific tasks.
“The number of hits and the distribution of impacts on different parts of the brain are directly related to the changes we are seeing in the fMRI data,” says Thomas Talavage, associate professor of electrical and computer engineering at Purdue an expert in functional neuroimaging.
Annually in the United States, 135,000 children and teens are treated in emergency rooms for sports- and recreation-related traumatic brain injuries, including concussions.
A new Indiana law requires student-athletes to be removed immediately from athletic activities if it is suspected they have suffered a head injury. In order to return to play, injured athletes must be evaluated and cleared by a health-care provider trained in head injury assessment.
In addition to Indiana, several states have passed laws governing the management of suspected head injury to young athletes, ranging from classes for coaches and referees to removal from play and evaluation by a physician trained in head injury assessment.
The research is being expanded to include an additional high school football team and both boys’ and girls’ soccer teams.
“We want to increase the number of football players in the study and also include soccer to study athletes who don’t wear head protection,” Nauman says. “We also want to include girls to see whether they are affected differently than boys.”
Findings represent a dilemma because they suggest athletes may suffer a form of injury that is difficult to diagnose.
“Most clinicians would say that if you don’t have any concussion symptoms you have no problems,” says Larry Leverenz, clinical professor of health and kinesiology and an expert in athletic training. “However, we are finding that there is actually a lot of change, even when you don’t have symptoms.”
Players in the study received 200-1,800 hits to the head in a single season, with two players receiving the maximum number. Helmet-sensor data indicated impact forces to the head ranged from 20 Gs to more than 100 Gs. “The worst hit we’ve seen was almost 300 Gs,” Nauman says.
A soccer player “heading” a ball experiences an impact of 20-50 Gs.
Findings could aid efforts to develop more sensitive and accurate methods for detecting cognitive impairment and concussions; more accurately characterize and model cognitive deficits that result from head impacts; determine the cellular basis for cognitive deficits after a single impact or repeated impacts; and develop new interventions to reduce the risk and effects of head impacts.
Researchers also will follow the case studies of players who take the most hits to see if there is evidence of permanent changes in brain structure using MRI scans.
The work is ongoing and is supported with grants from the Indiana State Department of Health Spinal Cord and Brain Injury Research Fund, General Electric Healthcare, and through the National Science Foundation and National Defense Science and Engineering Graduate Fellowships.