After becoming the first female U.S. boxer to win Olympic gold at the 2012 London Games, Claressa Shields was given a parade by her home town of Flint, Mich., and awarded a key to the city.

But the fame and endorsement deals that the 17-year-old hoped would follow never materialized, showered instead on telegenic swimmers, gymnasts and track stars who dazzled on NBC’s prime-time broadcasts.

At 5 feet 9 and 165 pounds, Shields doesn’t fit the traditional role of “Olympic darling” quite like a pint-sized gymnast or figure skater.

She hits for a living.

And soon after Flint’s celebration ended and residents got back to the soul-sapping grind of battling poverty, crime and under-employment, Shields dipped into her Olympic stipend to fend off the collection agency that was demanding payment of her mother’s overdue water bill.

Olympic gold medalist Claressa Shields incorporates dancing into her workout as she prepares for the 2016 Olympics in Rio. (Katherine Frey,Erin Patrick O'Connor/The Washington Post)

Entering the Rio Olympics, Shields, 21, is determined to make the world take notice in her second Olympics. She hasn’t lost a bout since London, improving her record to 74-1, and has won her sport’s last two world championships.

“I just got tired of waiting for endorsements and sponsorships, and I thought, ‘You know what? I have to make them respect me,’ ” Shields said in a recent interview. “‘I have to make them respect me even more.’ ”

Maybe the world isn’t ready to embrace the in-your-face power of a female middleweight champion with furious fists and a menacing competitive demeanor. Shields’s father, who brawled in unsanctioned fights staged in underground parking garages as a younger man, was uneasy about letting his daughter box.

“I don’t want you looking like a pair of scissors been used on your face when you get older!” Clarence “Bo” Shields remembers telling his 11-year-old when she begged for boxing lessons.

Out of the ring and without headgear, Shields’s face is luminous, with sparking eyes and a generous smile that broadens when she talks about her passions: boxing, children and the calling she feels to lift both in a harsh world.

Her own childhood was dark. She was 9 before she got to know her father, who began serving a seven-year prison sentence for breaking-and-entering when she was 2 years old. She was raped by her mother’s boyfriend at age 5, molested at 8. Her mother, an alcoholic, didn’t believe her story of abuse, so Claressa went to live with her grandmother, whom she considers her savior.

The Independent Lens documentary, "T-Rex: Her Fight for Gold," which airs Aug. 2, tells the story of Claressa Shields's journey to the Summer Olympics in Rio. It will stream for free on PBS.org through the month of August. (Independent Lens)

“I felt abandoned at a young age,” Shields said. “That’s where most of my anger came from, I guess. How does your mom not believe you?”

The father and the student

She grew tall and skinny, often going without meals so her younger siblings could eat. Bullied in grade school for her lanky appearance and what she describes as nappy hair, she took refuge in a diary from third grade on.

Writing helped her control her anger.

“If I wanted to curse you out, I would write everything I wanted to say to you in my diary, and it was like screaming in my head,” Shields explained. “After that, I would have no feelings for you; I wouldn’t be mad at you or upset because I already said it to you when I wrote it down. That’s what writing did for me.”

Boxing provided an even bigger release. Her father planted the seed.

“Look, I know you love me, and I love you,” he told her one day. “But you don’t really know me.”

So he told her about boxing, his own passion, and the life he might have lived as a professional fighter — if only he’d had someone to train and guide him.

Clarence Shields had been talented enough to make money in the fight clubs, competing under the name “Bo” (short for “bodacious”) or “Bo Cannonballs.”

“I had some boxing skills,” he said. “I hit awful hard, which is where the ‘Cannonballs’ came from.”

Then he told her about Muhammad Ali and the fact that of all of Ali’s children, the one who became a champion was his daughter Laila.

“I was telling her the story to say there wasn’t nothing in life you choose to do that you can’t achieve,” he explained.

But Claressa, who had recently been baptized, took it as a message from God that she was meant to fulfill her father’s unrealized dream.

After nearly a year of her begging, he signed up the 11-year-old Claressa for lessons at Berston’s Field House in Flint. She quickly stood out from the crowd of boys with her seriousness and determination to do everything trainer Jason Crutchfield demanded.

Being good at boxing made her feel secure. It gave her confidence. With gloves on, she could punch out the anger she’d scribbled down before. Boxing also gave her a surrogate family as her home life deteriorated.

She had no bed at her mother’s place and no guarantee of meals. She stayed for a time with an aunt, then with a teammate’s mother, frequently changing schools depending on which part of Flint she stayed. Friday nights and Saturdays, she’d plead with Crutchfield to open the gym so she could work out when no one was around.

On nights when she had no place to stay, she’d call Crutchfield to come pick her up. At 13, she moved in with her trainer, who became a father figure.

“He taught me manners. I used to eat with my hands,” Shields confides with a giggle. “We went out to eat, I was probably about 12, and I picked up a pancake and folded it. He said, ‘What are you doing!’ He was like, ‘No! You’re a girl. You’re a lady!’

“And he took his fork and he showed me that every time you eat, this is how you eat. It doesn’t matter how long it takes. He taught me that when I was about 12 years old, and I’ve been eating like that ever since.”

When Shields was 13, news came that women’s boxing would be added to the Olympics in 2012. Crutchfield guaranteed that she’d go, and he guaranteed that she’d win, telling her she already could beat the best female boxers in the world.

She looked at him like he was crazy.

And when the Olympic referee held her right hand aloft, and the announcer proclaimed her “gold medalist and Olympic champion,” Shields could only laugh, overcome with emotion.

Remaining close to her roots

Shields became the first in her family to graduate from high school the following year. But caring for her younger brother and sister, as well as her mother and an older brother who struggles with schizophrenia and bipolar disorder, proved exhausting as she continued training for a second Olympics.

So in May 2015, she moved to the U.S. Olympic Training Center in Colorado Springs, where room and board is covered. She also receives a monthly stipend, along with access to trainers, sparring partners, a masseuse, state-of-the-art gyms and coaches who understand her dark spells — the days when she wants to train in solitude, with only her gloves and bags.

But her hometown’s ongoing water crisis weighs heavily on Shields, who has used what clout she has to draw attention to the dire need of the city’s youngest for safe drinking water, free of the lead that now contaminates it. So when a tour group recently stopped by the boxing gym at the USOC training facility, she seized the opportunity in a brief exchange with curious visitors.

After vowing to bring home a second Olympic gold in Rio, she was asked where she was from.

“Flint, Michigan,” she replied. “That’s the one that’s going through the water crisis. We’re making it, though, so don’t feel sorry for us. Just send up some pallets of water!”

Then she mentioned a GoFundMe page she supports: Bottles 4 Babies. “You guys can go there and give money to help them drink water!”

Shields is a far more skilled boxer at 21 than at 17. Her hand speed is quicker. Her punches pack more power. And her repertoire is more varied.

“When I was 17, I probably knew two ways to box. Now I know at least 10,” she explained after a sparring session in which her rapid-fire punches reverberated like gunshots.

Before boxing, Shields dreamed of having 10 children by the time she was 26. She loves minding children, even the bad ones, convinced she can handle and protect them all. But motherhood is on hold just now. Becoming the first U.S. boxer — male or female — to win back-to-back Olympic gold is her priority.

After Rio, she might turn pro. She might try acting. She thinks she’d make a good teacher. She finally has an agent, Jamie Fritz, who’s helping publicize the inspirational potential of her journey and has landed deals with Powerade, Dick’s Sporting Goods and the Mini car company, among others. And an unflinching documentary that chronicles her road to the 2012 Olympics, “T Rex: Her Fight for Gold,” will debut Aug. 2 on PBS.

“When you look at where she has come from, among people of humble beginnings, she is another great example — a female athlete who has really gone through a lot and dealt with so much adversity,” Fritz said. “So many kids today deal with a lack of confidence, whether it’s because they wear the same shirt five days in a row or don’t have school supplies. Where is their confidence? I think Claressa is somebody they can look up to. The message is simple: If you work hard, you believe in something and you don’t listen to the outside noises, you can accomplish anything.”

One thing is certain: After Rio, Shields will leave Flint to stay. If they’ll come with her to Florida, she’ll also take her mother, sister, little brother and their two children.

But Flint and its children will always be part of her, and she intends to visit often to advocate for their needs.

“Kids in Flint don’t even know that you can write to express your feelings and go to the gym and work out, you can run, you can do whatever you love to help relieve stress,” Shields says. “My life is way bigger than boxing or acting or being rich or being famous or endorsements. I think God is using me, putting me on this high pedestal, so I can tell people about Him and tell people about where I came from and how I made it and, really, to make the people that feel broken, feel unbroken. That’s the journey I’ve been on.”