Most of us think helping an old college buddy means giving up a weekend to move a refrigerator.

Matt Birk is giving away his brain. Literally.

"I filled out the paperwork right before training camp," said Birk, the former six-time Vikings Pro Bowl center who signed with the Baltimore Ravens as a free agent this past offseason.

And how did that make you feel, Matt?

"A little creepy is how I'd describe agreeing to donate your brain," Birk said. "They had to talk to my wife and make sure that she's aware of the agreement in case something happens to me and I'm not able to declare my wishes when it's my time. That's a little uncomfortable talking about, but there's a bigger picture here."

Birk has joined Seattle linebacker Lofa Tatupu and Arizona receiver Sean Morey as active NFL players who have agreed to donate their brains and spinal cord tissue after death to Boston University's Center for the Study of Traumatic Encephalopathy. Researchers at the center are trying to understand the long-term effects of sports brain injuries, with the ultimate goal being to improve player safety for future generations.

One of those researchers is co-director Chris Nowinski, one of Birk's former teammates at Harvard.

"I actually hosted Chris on his recruiting trip to Harvard," Birk said. "Fast-forward a few years later and I saw what he was doing and some of the results they were finding from the examinations they did on dead football players. It was pretty alarming."

Doctors have discovered the neurodegenerative disease Chronic Traumatic Encephalopathy in several athletes who had recently died. The disease is caused by repetitive brain trauma and includes symptoms such as memory loss, emotional instability, erratic behavior and depression.

Birk has suffered three concussions in his life: one while playing at Cretin Derham-Hall, one at Harvard and one with the Vikings. He is also concerned about what the long-term effects are of spending decades banging helmets every day in practice and in games.

"It's something that we don't like to talk about as players because I think we're afraid of what could happen to us years from now," Birk said. "But what they were finding at Boston University was pretty eye-opening, so I wanted to do my part and help out. I think all of us as players should try to do whatever we can to help improve player safety for the guys who come after us."

There are 40 retired NFL players who are on the center's brain donation registry. Birk is hoping that three current players, each of whom has been to the Pro Bowl, will help encourage more to follow.

"There's a small window of opportunity for me to raise awareness," said Birk, a 12-year veteran. "Once you're out of the game, you really don't have a loud voice."

This isn't Birk's first crack at raising awareness for the brotherhood of professional football players. He is the leader among current players in the Gridiron Greats Assistant Fund and has been an outspoken critic of what he and others believe is the mistreatment of former players in need by the league and its players union.

"Matt Birk is one of those guys I've played with who has a bigger picture in mind while he's still playing the game," Vikings kicker Ryan Longwell said. "He understands what we do is we play a game. It's not life and death. There's a bigger picture to him, whether it's charity work or helping retired players or now this."

Birk said he didn't have to give this decision a lot of thought once his old college buddy got him up to speed on the research.

"Pardon the pun," Birk said with a laugh, "but it's kind of a no-brainer."