Avery Pontell-Schaefer is encouraging people to realize that fit doesn't look a certain way.

By Faith Brar

Avery Pontell-Schaefer (aka IronAve) is a personal trainer and a two-time Ironman. If you met her, you'd think she was invincible. But for years of her life, she struggled to have confidence in her body and what it could do-simply because it was built differently.

"Growing up, I never allowed myself to think that I was an athlete," Pontell-Schaefer tells Shape. "I was different than the girls around me. I wasn't the skinny or toned-looking girl that people think of when they imagine someone fit." (Related: Candice Huffine Explains Why "Skinny" Shouldn't Be the Ultimate Body Compliment)

But Pontell-Schaefer was an athlete-a good one at that. "I was a phenomenal swimmer," she says. "My coach literally called me 'Ave The Wave.' But because of my build and because I didn't look like I was capable, I never let myself believe that I could run a 5K, let alone complete an Ironman."

For years, Pontell-Schaefer gave into the notion that she could never be "fit" like other girls-and that her body wasn't capable of doing tough workouts. In college, being active wasn't a priority to her. And even into early adulthood, she says she struggled to find a workout that made sense for her. "There just wasn't anything that I was dying to try, but I knew I wanted to start being active again," she says.

In early 2009, a few years after college, Pontell-Schaefer was presented with the opportunity to do a triathlon for the first time. "My mom had never done a triathlon before and really wanted me to do it with her," she says. "The thought of swimming in lake water next to a bunch of people, and then running and biking, sounded absolutely insane to me. But my mom started training and was so excited about it-and I thought if she could do it, I literally had no excuse." (Related: How Falling In Love with Lifting Helped Jeannie Mai Learn to Love Her Body)

And she did it! She completed her first triathlon a couple months later, and Pontell-Schaefer fell in love with the sport. "I was bitten by the bug," she says. "It was like my life had been at a standstill and my wheels were finally turning. There was also an incredible sense of empowerment in knowing that I could complete a triathlon, that I was strong enough, that I was good enough." Race by race, Pontell-Schaffer began pushing herself to see what her body was capable of, eventually graduating to half-Ironmans.

Then, the following year, Pontell-Schaefer completed her first Ironman. "At that point, I had come a long way in changing my mindset about what my body could do," she says. After crossing the finish line, she had a revelation of sorts. "I wanted everyone to feel what I was feeling," she says. "So a couple months later, I quit my 10-year-long corporate career and decided that I was going to dedicate my time to helping others like me realize their full potential." (Related: How Olympic Gold-Medalist Gwen Jorgensen Went from Accountant to World Champion)

Since then, Pontell-Schaefer has dedicated her time to becoming a trainer at an Equinox Sports Club in Manhattan and an ambassador for Ironstrength, a workout series that focuses specifically on injury prevention for endurance athletes. She recently founded IronLife Coaching, a training program that specializing in running, triathlons, swimming, and nutrition. Next up: She's gearing up to run the New York City marathon in November.

"If you'd told me this was going to be my life 10 years ago, I would have laughed and called you crazy," she says. "But this whole journey has been a reminder that your body is an incredible machine and can do whatever you want it to with the right training and resources." (Related: How Anyone Can Become an Ironman)

Along the way, Pontell-Schaefer has lost weight and molded her body to be in the best shape it's ever been. But for her, it's not about the number on the scale. "I'm not training to be skinny, I'm training to be strong," she says.

"I think if more women adopted that mindset, they might surprise themselves with their body's ability, and frankly could be happier with themselves just as they are. I'm very proud of my body, both in the way it looks, and the way I feel, and what it can do." (Related: This Fitness Blogger's Post Will Change the Way You Look at Before-and-After Photos)

Pontell-Schaefer says she still receives shocked comments sometimes when she shares that she's an Ironman-but she doesn't let what others think about her body get to her the way she used to. "There's joy in surprising people and broadening their minds to the idea that being fit doesn't look a certain way," she says. "Not to mention, when people learn that they've underestimated me, they learn that in turn, they might also be underestimating themselves. There might be things that they can do even though society tells them they can't. They just haven't found the courage to give themselves a chance yet."

"I just hope that whoever is reading my story realizes that they are limitless," she continues. "I'm a firm believer that the only limits in life are those you put on yourself."