Student athletes experience brain changes, even when they have not suffered concussions, according to a new study examining high school football players.

Concussions are often seen in student athletes, and these injuries, which can lead to brain damage, have caused a great deal of concern from parents and school officials. High school football players could damage their brains from injuries less severe than concussions, according to a study matching electronic measurements of impacts with brain examinations.

Wake Forest Baptist Medical Center researchers studied 24 high school football players, between the ages of 16 and 18, who had never experienced a concussion. Players were divided into two groups - 15 were classified as light hitters, while nine were marked as heavy hitters. Accelerators were placed in the helmets of the players, so investigators could quantify the forces applied to the head during collisions.

High school football players were found to exhibit changes to their brains after just a single season of playing the sport, despite the fact they never suffered a concussion while on the field. Those students who were hit on the head most often experienced the greatest amount of damage.

"It's not the harder the hit, it's the cumulative exposure to impact," Christopher Whitlow, from the Radiology Translational Science Institute at Wake Forest Baptist Medical Center in North Carolina, said.

Diffusion tensor imaging (DTI) was used to examine the white matter in students' brains. These nerve fibers act like communication lines, connecting various parts of the neural structure. Water moving through these cables, called fractional anisotropy (FA), was traced using DTI.

Water usually moves fairly evenly between different areas of the brain, which is measured as a high value for FA, a number between zero and one. Over the course of a season, football players in the hard-hitter group were found to have a lower FA than light-hitters. None of the players in the study experienced a concussion during the course of the season.

More head collisions were reported during practice sessions than during actual games, according to researchers. The study started with accelerometers set in helmets of 40 student athletes, but researchers were only able to collect enough data from 24 subjects for use. Video recordings were used to ensure impacts recorded for the study occurred during play, and not from helmets being thrown or stored away.

This study could provide further evidence to recent concerns that repeated blows to the head could lead to brain damage. Results of the investigation were reported at a press briefing at a meeting of the Radiological Society of North America.

"It is unclear whether or not these effects will be associated with any negative long-term consequences," Whitlow said.