ENGLEWOOD, Colo. -- David Bruton Jr. turned 30 on Sunday, an occasion he said would include "a mountain bike with me on it." He will complete a summer chemistry class on Thursday, and he has a to-do list that is chock-full of "my new life" as he looks at what’s to come.

The future is now for Bruton, as the longtime special-teams captain of the Denver Broncos formally announced his retirement from the NFL on Monday. The self-professed “nerd of the locker room" said that a combination of health concerns -- he said he’s had six concussions in his eight-year career -- paired with a loss of passion to prepare for the game and his eagerness to get to the next life step brought him to his decision.

“I’m burnt-out, definitely worry about my health," Bruton said. “Another season was cut short by a concussion [in 2016] -- that’s six. I’m a guy who likes to use his brain. Especially back in school, I need as many brain cells as possible with all these science classes. It came down to health, and I’ve definitely had my time in the league. I’m ready to move on."

Bruton, who graduated from Notre Dame before entering the NFL in 2009, is already back in school at the University of Colorado-Denver. He has begun what he says will be a five-year journey to become a physical therapist in his post-football life.

To that end, he has been an intern at Next Level Sports Performance in Golden, Colorado, and will work with the Broncos’ training staff during training camp.

“I thought about professional mountain biking," Bruton said with a laugh. “I don’t know if they have a great concussion plan. But physical therapy is definitely something I’ve always wanted to do. To see the people who enjoy doing it, who are good at it, and seeing the reward they get with working with people who work so hard to get back to normal life -- it’s so rewarding."

Bruton played 108 games in his NFL career -- 104 with the Broncos. He was a longtime special-teams captain, a respected voice in the locker room. As the Broncos powered through the 2015 season on the way to victory in Super Bowl 50, Bruton was the longest-tenured player with the team, having been a fourth-round pick in 2009.

Champ Bailey, who played the bulk of his Hall of Fame-worthy career in Denver, routinely pointed to Bruton as a player “who does it like guys should do it -- [Bruton] knows what he’s supposed to do and what everybody else is supposed to do too."

But how the 2015 season ended -- the Broncos put Bruton on injured reserve in December with a fractured fibula because they feared he wouldn’t be healed in time for the postseason, so Bruton was not in uniform for the Super Bowl -- and how his final season unfolded in Washington in 2016 weighed heavily in his decision. Bruton suffered a concussion in the Redskins’ fourth game, and eventually the Redskins put him on injured reserve and later released him.

“I thought I was ready to come back for the playoffs [in 2015]. I did a full workout before the Super Bowl but was already on IR. So I still went into last season thinking I’m going to at least see 10 years ... that concussion happened, being cut happened, the ugliness of the business was really exposed," Bruton said. “But the bottom line is I want to do other things. I’m ready to move on."

David Bruton Jr. played 108 games in his NFL career, 104 with the Broncos. He was a special-teams captain and a respected voice in the locker room. AP Photo/David Richard

The Broncos are expected to recognize Bruton’s contributions to the team now that he has formally announced his retirement. He and the Broncos always had football love for each other, but it was often tough love. A safety, Bruton was consistently one of the smartest, most athletic players on the team, but the Broncos often seemed to be searching, through three head coaches and five defensive coordinators, for someone else to play instead of him.

“So I made sure I excelled on special teams," Bruton said. “You can make an impact with the team, make an impact in the community, make a career for yourself. It always angered me, always motivated me to work. I don’t know what it was. I took my role very seriously no matter what it was. But when you’re living it, it’s always tough to constantly see somebody else get drafted."

Bruton said a workout with the Baltimore Ravens earlier this year, one that “did not go well at all, because I just didn’t have it in me anymore to do it," was one of the last indicators football is no longer for him.

As he moves into this next career, he will continue with his Bruton’s Books program to put books in the hands of children and improve reading skills of at-risk elementary school students. During the 2011 NFL lockout, Bruton worked as a substitute teacher in Miamisburg, Ohio, and he was the Broncos’ Walter Payton Man of the Year in 2015 for his charitable endeavors.

He said he allows his son, Jaden, to play football, but wishes Jaden had waited a little longer to take up the game. Jaden will be a sixth-grader this coming school year.

"I started playing in seventh grade," Bruton said. “But he’s been playing since third grade, I haven’t been a fan of that. I advise to start later; football can wait. If you can eliminate that contact until you get older, I think it’s better.

“But my family, my parents, my brother, everyone, they’re very happy with what I did, and with what I’m going to do now after football. Especially my mom [Constance]. She wanted me to hang it up after the last concussion. But I’m excited about what’s next."