Boxer Claressa Shields' Long Fight for Olympic Glory

— -- Olympic boxer Claressa Shields has come a long way from the gritty streets she grew up on.

The 21-year-old has 75 wins, two world championships and an Olympic gold medal under her belt -- she won her first gold in 2012 when she was just 17. Now she's competing in Rio at the 2016 Games to go for gold a second time. Only two other women in history have won Olympic gold in boxing, which happened in 2012 when women's competition boxing was included in the Olympics for the first time.

"I enjoy fighting. Period," Shields said. "I just enjoy being able to show someone I can outbox them."

"I'm an athlete. I'm a boxer," she continued. "I'm just as fast as you. I'm just as strong as you. I'm just as skilled... I get to fight without going to jail. You fight in the streets, you get locked up."

Growing up in Flint, Mich., which has been plagued by gang violence and a drinking water crisis, Shields learned to fight for everything. There's a lot riding on her powerful shoulders, including helping to take care of her family.

"I don't really let anything be pressure to me," Shields said. "I don't know why. I kind of just accept it. I just do it, accept it, but I want to help my family."

Oddly, the boxing ring, where people pummel each other, was always her refuge.

"I know some people that were killed but they were into gang violence and the wrong kind of people," Shields said. "It's still hurtful and I miss a lot of my friends."

But Shields wasn't spared from all violence. In the PBS documentary, "T-Rex," she said she was raped as a child. Shields said she decided to share her story after she heard another young women recount her horrible childhood experiences.

"I had went to the University of Michigan-Flint. There was a girl who was talking about her mom who sold her for some drugs," she said. "She was 17 and for her to get up there and tell her story, I was like, 'I would never.' ... I felt like a coward."

"I was like, 'look at me on this huge pedestal,' and you know, 'boxing is my way out and not telling my story,'" Shields added. "So me hearing hers made me decide I would speak about it."

But it's a story that she chooses not to use to define herself.

"That's not my story, that's not why I box," she said. "I like boxing because I walk into the gym and everyone was working hard. That's why I like boxing. Me being raped and molested has nothing to do with that."

Shields met her longtime trainer Jason Crutchfield at Berston Field House, a boxing gym in Flint. When he first saw her come in, he didn't pay much attention.

"I didn't want to mess with no female boxers," he said. "I didn't believe in female boxing... and she was doing better than the boys."

For eight years, Crutchfield guided her through every punch.

"She would be the first one here every time," Crutchfield said. "I say, 'OK, be down to Berston at 8 o'clock.' She would be here at 6 o'clock in the morning.'"

In preparing for the London Olympics in 2012, Shields split her time between training and high school, living in six different homes.

"I was moving everywhere," she said. "Making my own decisions, trying to make the right decisions in my life."

But Shields believes her traumatic childhood is one of the sources of her strength -- and boxing was her way out.

"Everyone is different," she said. "I definitely think I'm tougher than most of them... I guess I can blame it on my upbringing and where I'm from, but at the end of the day, we're all fighters no matter where we come from."

And she's taken her setbacks. Despite winning gold in London, Shields received fewer endorsements than her counterparts in other sports, though this time around, endorsements are coming in. Just a few months before the 2012 Olympics, Shields went into the world championships undefeated and experienced her first and only loss of her career to date.

Even still, she's the favorite to win gold at Rio, and she continues to push for glory, fist over fist.

"If I win a second gold medal, I believe I should get a freakin million-dollar deal to go professional," Shields said. "Two Olympic gold medals at the age of 21? Oh, come on, there's no way I shouldn't."