Smaller than most of her peers and lacking self-confidence, she was an easy target. She began to withdraw and avoid social gatherings. Her father, Scott, a professional boxer and coach, coaxed her into the gym, promising her it would not only help her defend herself physically, but give her the confidence to rise above the bullying.

She was skeptical at first.

“I was the only girl in a gym full of sweaty guys,” Sierra said during a recent workout at the Gamache Boxing Club in the bowels of the Lewiston Armory.

After nearly four decades of churning out world-class boxers, including his son Joey, a three-time world champion, Joe Gamache Sr. still enjoys training not only potential champions, but spending time with “kids who are just doing this to get in shape, stay off the streets and away from the television. I keep track of their grades and make sure they know that is the most important thing in their lives right now.”

When Sierra started to train, she immediately began to feel stronger, not only physically, but mentally. Her confidence grew, and she began to confront the peers who were harassing her, she said.

“At first I used my fists and got into trouble. I realized that was not the way to solve my problems, so I began to confront the bullies, trying to talk things out, she said. “Having the confidence of knowing I wasn’t going to get beat up helped, but I now have both skills to help me get through. All I want is to be respected. Now I take out all my frustrations in the gym during my workouts.”

With two hours of strenuous training five days a week, there is plenty of time to release her tension and frustrations. Her workouts start with jumping rope, three rounds of shadow boxing, speed and heavy bag punching, and stretching before stepping into the ring.

Once in the ring, all the boxers work in unison as a loud bell sounds to signify the start and finish of a round, where they rotate through a series of arm, leg and core exercises. When that part of the session is complete, some begin to spar while others do more training outside the ring. During a recent training session with Joe Sr. wearing training mitts, she threw more than750 punches in one round.

Gamache Sr. said he has high hopes for Sierra. The 132-pound weight class fighter is 3-0 in her career. That includes being the reigning New England Silver Mitts champion, a tournament for boxers too young to compete in the Golden Gloves Tournament.

“This young girl, she looks like an angel, but fights like the devil,” Gamache said. The 15-year-old is focused and committed, with some defined goals.

“Right now I am concentrating on keeping my grades up, head on straight and working toward fighting in the 2020 Olympics, she said.