"The goal here is that research discoveries and medical advances will have a watershed effect on all of football," Nabel said during a news conference in which she shared recommendations made to NFL Commissioner Roger Goodell.
Nabel was joined by a panel of other doctors who advise the league, and who stressed that more research is needed to advance the current understanding of repetitive head injuries -- and other types of injury.
Nabel said another goal is to draw awareness to the behavioral health of athletes, and to better understand "the incidence and prevalence of depression, suicide, substance abuse and other behavior issues not only in football, but in other sports,"
A cardiologist, Nabel is the president of Brigham and Women's Hospital in Boston and a professor at Harvard Medical School. She was appointed by the NFL in February to help oversee the league's medical strategy in advancing player safety. The move came after reports of long-term health issues among former football players who had a history of concussions -- and criticism of the league's handling of the issue.
Prevention is a major part of the overall effort.
Among the changes in recent years, according to the NFL, has been conducting pregame medical assessments of players, along with on-field and postgame assessments of players involved in hard hits. Another has been moving the kickoff spot five yards forward, to the 35-yard line, thus reducing the number of kickoff returns.
"What this has resulted in over the past three years is a 25% reduction in concussion, 40% reduction in helmet-to-helmet hits," said Dr. Russ Lonser, chairman of the NFL's Head, Neck and Spine Subcommittee.
Nabel told CNN, "Really, the goal is to provide protective equipment and to adjust the rules and the policies to minimize injury and really maximize the healthy component of the sport."
Head trauma risks haunt league, players
Reports show an increasing number of retired NFL players who have had concussions
have developed memory and cognitive issues such as dementia, Alzheimer's disease, depression and chronic traumatic encephalopathy (CTE)
Concerns about such risks prompted Chris Borland, who was a rookie linebacker for the San Francisco 49ers last season, to walk away from a promising pro football career at the age of 24
Last month, a federal judge approved a settlement
in a class action lawsuit between the NFL and thousands of former players. It calls for the payment of up to $5 million to each retired NFL player who suffers from specific medical conditions associated with repeated head trauma. The players accused the NFL of hiding the dangers of concussions.
"There's a lot that we don't know yet about the long-term health issues and long-term safety issues...we're just at the beginning," Nabel said.