The National Football League (NFL) has built an empire on top-heavy men throwing themselves at each other for the sake of sport. Until recently, the league showed little interest in making sure its players were safe: injuries were simply “part of the game.” But now medical science and droves of NFL alumni, many of whom suffer from lifelong brain injuries, are insisting the league set protective guidelines for its current players and warn them of the risks.

The latest research into football’s traumatic effects compared the number of times a player reported getting sidelined after a nasty hit with how his brain was functioning during certain tasks. Published in Scientific Reports, the study collected 13 former NFL players and 60 healthy volunteers to sort colored balls into various tubes. Participants were told to sort the balls in as few moves as possible. Ultimately, the team of researchers found the NFL players’ brains showed hyperactivity and hypoconnectivity while performing the task, which suggested to them that NFL players may be more likely to “experience certain executive dysfunctions” as a result of their profession.

“The sensitivity has changed dramatically over the last, probably, five years,” Howard Katz, senior vice president of media operations for the NFL, told the New York Times. Katz also served as president of ABC Sports, which broadcast Monday Night Football through 2005. During his time there, he said, “Nobody thought anything about the crashing helmets and the implication of the crashing helmets.”

League officials have since taken more hardline stances regarding head-to-head collisions. As of March of this year, players can longer tackle their opponents by leading with the crown of their helmet. Called the “Tuck Rule,” the act of leading with the helmet was once a favorite among many of the league’s more vicious athletes. Now the foul carries a 15-yard penalty and the risk of heavy fines, although the strictness with which referees enforce the rule is suspect.

What’s clearer, especially to scientists, are the effects of non-intervention. One 2009 study from the Michigan Institute for Social Research surveyed ex-NFL athletes about their brain health, and the numbers are telling. Among players 50 years and older, 6.1 percent reported having received a diagnosis of “dementia, Alzheimer’s disease, or other memory-related disease.” That rate is five times the national average for that age group. Worse, players aged 35-49 saw a diagnosis rate 19 times the national average.

“There is something wrong with this group as a cohort,” neuropathologist Bennet Omalu told The New Yorker. In 2002, Omalu was the first person to diagnose an ex-NFL athlete with chronic traumatic encephalopathy, a neurodegenerative disease that causes similar effects as dementia. Omalu now works extensively with ex-athletes, as many suffer from debilitating injuries.

“They forget things. They have slurred speech,” Omalu added. “I have had an NFL player come up to me at a funeral and tell me he can’t find his way home.”

Luckily, some great strides are being made in the NFL to relieve the enormous burden felt by CTE sufferers and other athletes with mental illnesses. Just before the start of 2013-2014 season, the league agreed to a settlement to the tune of $765 million to fund medical exams, compensate sufferers, and facilitate research. Since 2011, more than 4,500 of the 18,000 total retired athletes have sued the league for damages, arguing that the dangers of the sport weren’t made clear when they signed their contracts.

"This agreement lets us help those who need it most and continue our work to make the game safer for current and future players,” an executive vice president at the NFL told the Telegraph. "We thought it was critical to get more help to players and families who deserve it rather than spend many years and millions of dollars on litigation."

Out of that settlement, $10 million will go to research and $75 million will be set aside for medical exams. The remainder will go toward compensating retired athletes.

Moving forward in the NFL requires a commitment to what science has professed for over a decade, that heavy exposure to sub-concussive force over time degrades brain tissue and, subsequently, brain function. The problem is, football relies on big hits to keep fans entertained. Long passes or breakout runs add flavor, but in a sport built upon an ethos of war and grit, bone-crushing tackles are essential.

“I think that Peyton Manning or Tom Brady throwing long touchdown passes or LaDainian Tomlinson or Chris Johnson running 70 yards for a touchdown is just as exciting and appealing, and it’s all part of the game,” Katz told the New York Times. Still, “it is a very physical game, and there’s no denying that.”