Jimmy Gjere, an offensive lineman for the Gophers football team from 2010-12, quit after three diagnosed concussions and side effects like increased moodiness and memory problems.

Since his first diagnosed concussion, Gjere said, his doctors have come a long way in understanding the implications of his injuries. But there’s still a lot that experts don’t understand.

The Journal of Neurosurgery published a study last month comparing the relative risk of concussion for players wearing two different types of helmets. Before this research, no data had been collected to prove that helmet design could affect football players’ risk of concussion.

The study collected data from more than 1.2 million head impacts and found that players wearing a Riddell Revolution helmet experienced about one concussion for every 26,000 impacts. Players wearing a Riddell VSR4 helmet experienced about one concussion for every 12,000 impacts. The researchers at Virginia Polytechnic Institute and State University collected data from eight college football teams, including the Gophers.

“The point of the study wasn’t necessarily to compare those two helmets, but it was to answer the general question of whether there were differences in risk reduction in different helmet types,” said Steve Rowson, assistant professor in biomedical engineering at Virginia Tech and the study’s lead author.

“If these helmet types have differences,” he said, “then other helmet types will have differences, too.”

The Centers for Disease Control and Prevention describe a concussion as a type of traumatic brain injury, caused by a blow or jolt to the head that has the potential to change the way the brain functions.

The CDC estimates that 1.6 to 3.8 million concussions happen across all sports each year.

But data from the NCAA show those numbers represent only a fraction of total concussions in a given year. The highest rate of these concussions occurs in football, according to the Virginia Tech study.

During his time with Gophers football, Gjere said, his coaches and training staff took necessary precautions to avoid concussions on the field. The staff fitted all helmets multiple times a year, made sure they were strapped correctly and emphasized proper training.

But if an older helmet still fit and hadn’t encountered problems from a previous year, it often wasn’t replaced, Gjere said.

The call for more research

Another high-impact sport on campus doesn’t use helmets at all.

Rob Holder, head coach of the University of Minnesota’s men’s rugby club, said rugby has been around a lot longer than football, and no one has ever made the decision to put helmets on players. But because of that, players take fewer high-impact risks.

For instance, rugby players are taught to tackle with their shoulders — rather than their head, like in football — and a player can’t be tackled unless they have the ball. Holder said rugby players also don’t experience whiplash injuries as often as football players because rugby collisions aren’t as extreme.

Diane Wiese-Bjornstal, an associate kinesiology professor at the University, said this increased caution demonstrates “risk compensation” theory, which says that people modify their behavior based on the level of risk they perceive.

The University treats concussions the same as other health institutions do, said Donald Dengel, a kinesiology professor who does concussion research at the University. Health experts suggest mental and physical rest for at least a couple of weeks after the injury and then a gradual recovery.

Often, concussions can have long-term side effects like depression or memory loss. But researchers are still confirming this on a large scale, Wiese-Bjornstal said.

Dengel has a grant funded by the NFL Foundation to explore how multiple concussions affect blood vessel function inside the brain and how those long-term effects relate to cognitive function. He said he hopes the work will improve the monitoring and diagnosing of concussions.

But for the most part, not much is known about concussions and research is ongoing, Wiese-Bjornstal said.

“I worry that a person may think, ‘I have the latest, greatest helmet, so I can do whatever with my head,’ and then they won’t respect their head,” she said.

Rowson, the Virginia Tech researcher, said no helmet will prevent all concussions and there will always be injuries in high-impact sports. The best way to avoid concussions, he said, is to teach better technique on the field.

But Gjere said that even with this research, he isn’t confident future players will experience fewer concussions.

“I think there definitely could be more research, but it gets to the point that how much research — how much can you actually do?” he said. “It’s still a violent game.”