(HealthDay News) — There’s been a lot of discussion recently about concussions and contact sports, but new research suggests that even less severe head injuries might lead to brain changes among high school football players.

The study found that repeated blows to the head after just one season could cause measurable changes in the brains of young athletes who never had a concussion.

The more often the athletes were hit, the more evidence they showed of brain changes that appeared abnormal, according to the study’s author, Dr. Christopher Whitlow, an associate professor at the Radiology Translational Science Institute at Wake Forest Baptist Medical Center in Winston-Salem, N.C.

“It’s not the harder the hit, it’s the cumulative exposure to impact,” Whitlow explained.

The study involved 24 high school football players between 16 and 18 years old. None of these athletes had ever experienced a concussion. During every practice and game, the participants wore helmet-mounted accelerometers, which tracked how often and how hard they were hit.

Based on this data, the players were divided into two groups. Nine of the athletes were considered heavy hitters, and 15 were considered light hitters.

Using an advanced brain imaging technique, known as diffusion tensor imaging (DTI), the researchers then looked for changes in the white matter of the players’ brains.

White matter is made up of millions of nerve fibers that work like communication cables connecting various parts of the brain. DTI provides a measurement of the movement of water along these nerve fibers, known as fractional anisotropy (FA).

In a healthy brain, the movement of water is even and has high FA. More random water movement and a drop in FA, however, suggest brain abnormalities.

Although none of the players sustained a concussion, by the end of the season the players in the heavy-hitter group had more significant decreases in FA in certain parts of the brain than those in the light-hitter group, the researchers noted.

There is mounting evidence that repeated hits to the head — including those that do not result in concussion — may be cause for concern, according to Dr. Robert Stevens, an associate professor in the division of neuroscience critical care at the Johns Hopkins University School of Medicine in Baltimore.