We all cringe when football players get steamrolled by opponents on the gridiron, but it turns out that minor hits can cause just as much damage over time.

A new study shows that even small hits to the head can cause concussions and permanent brain damage if they are repetitive enough. The study, published in the Annals of Biomedical Engineering, examined whether repetitive head impacts affected the chances of football players getting a concussion.

They matched 50 players who played the same positions in NCAA football, except one group suffered from concussions, and the other didn’t. They found that 73 percent of players with concussions experienced repetitive head injuries in the days leading up to their injury. This was even worse for athletes that took part in more contact activities.

"This unique analysis provides further evidence for the role of repetitive head impact exposure as a predisposing factor for the onset of concussion among Division 1 college football athletes," says Brian Stemper, the study’s lead author.

"While these trends require further validation, the clinical implication of these findings supports the contemporary trend of limiting head impact exposure for college football athletes during practice sessions."

He also suggests that this is further support for head protection in contact sports such as football. And if the NCAA is serious about finding ways to protect the head, they should look into allowing players to use medical marijuana, which can both reduce the ill effects of head injuries and make the brain more resilient to traumatic impacts.