(dailyRx News) Parents of high school football players take note: it's not the one big hit that poses the greatest risk to their teens' brains - it's the smaller hits from regular practices and games.
A recently published study based on two football seasons at Jefferson High School in Lafayette, Ind. provided evidence that the players are sustaining head trauma that alters their ability to perform certain tasks - even if they never had a major hit to the head.
Evan Breedlove of the School of Mechanical Engineering at Purdue University led the study of 21 players in the first season and 24 players in the second season, including 16 players who participated during both seasons.
The researchers used data from head impacts gathered from helmet sensors as well as brain-imaging scans called fMRIs and cognitive tests given to the players.
Although six players sustained concussions across both seasons, 17 other players showed changes in their brains despite not having had concussions.
Helmet sensors showed each player received between 200 and 1,900 hits to the head in just one season, with impact forces ranging from 20 Gs (about the impact of heading a soccer ball) to over 100 Gs. Two players had over 1,800 hits.
The scans revealed that the players are using different parts of their brains for certain tasks - implying that their "functional capacity is reduced" in some areas, according to Thomas Talavage, PhD, an engineering professor at Purdue and one of the study's coauthors.
He said the amount of change the researchers saw in the fMRI images correlated with how many hits the players took and where they took them.
The players still appear able to perform the tasks at the same ability level, but they may not use the same parts of their brains that they did earlier in the season.
"The most important implication of the new findings is the suggestion that a concussion is not just the result of a single blow, but it's really the totality of blows that took place over the season," said Eric Nauman, an associate professor of mechanical engineering and co-author who specializes in central nervous system and musculoskeletal trauma.
"The one hit that brought on the concussion is arguably the straw that broke the camel's back," Nauman said.
Dr. Daniel Clearfield, DO, is a sports medicine and concussion specialist who told dailyRx he deals with these issues quite often, both in football and in soccer.
"These athletes suffer sub-concussive blows to the head repeatedly in practice and on game-day, and these occult injuries add up over time," said Clearfield, also an assistant professor of orthopedic surgery at the University of North Texas Health Science Center.
"I personally believe we need to see a regression in the football helmet so that players don't feel like they have a 'safety net' on their heads," he said.
He also believes heading the ball in soccer should be introduced at a more advanced age because "the younger brain, the more susceptible to acute and long-term injury."
This study is limited by the small number of students - all males - who were studied, but it suggests that how many times a player gets hit at all may be more important to consider than which players may sustain the biggest hits.
The brain changes revealed in the fMRI scans occurred in parts of the brain associated in previous studies with chronic traumatic encephalaopathy (CTE), a disease that occurs in people who have multiple concussions or other head injuries.
Often the diagnosis of "punch-drunk" boxers and professional football players, CTE worsens over time and has been linked to depression, dementia and decreased cognitive function.
"This is still circumstantial evidence, but it suggests that whether you are concussed or not your brain is changing as a result of all these hits, and the regions most affected are the ones that exhibit CTE," Nauman said.
"Now that we know there is definitely a buildup of damage before the concussion occurs, ultimately, there is hope that we can do more to prevent concussions," he said.
The same team is working on a larger study that investigates an additional high school football team as well as a girls' soccer team. They will follow the players from this study who sustained the most number of hits to see if they have brain changes over time.
The research will appear online in the Journal of Biomechanics. No conflicts of interest were noted for the study.
The study was funded by grants from the Indiana State Department of Health's Spinal Cord and Brain Injury Research Fund, General Electric Healthcare, the Indiana Clinical and Translational Sciences Institute, the National Science Foundation and the National Defense Science and Engineering Graduate Fellowships.