Former football star Herschel Walker and former heavyweight champion Larry Holmes say they are all too aware of the toll that blows to the head can take on an athlete's brain.

In remarks Tuesday during a Capitol Hill news conference on brain research, Holmes introduced himself by recounting his record — 75 fights, including 69 wins with 44 by knockout.

"My intent was not to hurt anybody," said Holmes, appearing with boxers Paulie Malignaggi and Austin Trout and mixed martial artist Phil Davis. Mentioned throughout the news conference was heavyweight great Muhammad Ali, who suffers from Parkinson's disease.

Sen. John McCain, R-Ariz., and Dr. Charles Bernick of the Cleveland Clinic's Lou Ruvo Center for Brain Health joined the athletes in thanking corporations for their support — and to welcome a noteworthy development: The Nevada Athletic Commission will now require all fighters to undergo brain testing.

Bernick, who said there are more than 650 fighters — men and women — in the study, said he hopes other sports commissions follow Nevada's lead.

Walker, a star running back involved in the mixed martial arts, called the ongoing research into brain damage a blessing.

"In my former field, they're not going to know about it until you're dead," he said.

Scott Coker, president of the mixed martial arts promotion company Bellator MMA, and Kevin Kay, president of the cable network Spike, also attended the news conference. Both have donated to the research.

McCain has focused on boxing, its impact and the research. He described himself as an "avid boxing fan and mediocre boxer."