She developed diastasis recti, where the abdominal muscles split during pregnancy to make room for a growing baby, creating a cavity in the middle of the stomach. And while Bruce was thrilled to have her two sons, the elite runner was having trouble figuring out her body again.
"It was really hard physically on my body and mentally, and as I was going through some things trying to get back into training, I was like, 'Does this happen to all women?' " Bruce, 32, tells PEOPLE. "No one told me all of this."
"So as it was happening to me, I felt like I just wanted to be real about it, and put it out there."
Bruce has proudly shared photos of her postpartum progress from day one, with her pregnancy belly still showing right after the birth of her second son in Sept. 2015, to today, as she prepares for the Olympic Trials in the 10,000 meter run and continues to rebuild her core, stretch marks and all.
"When I started back running again, I could barely run a 9 minute pace, versus when on easy days when I'm in shape I could run 7-7:30 pace, and I was having a lot of bathroom issues, I couldn't control peeing, I had bowel incontinence, so I was going to the bathroom on a run," Bruce says.
"And it wasn't just not feeling like a pro athlete, I didn't even feel like a functioning human at that point, because that was just so demoralizing and a little humiliating to feel like, that I couldn't even control going to the bathroom."
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Her honesty gave her plenty of fans, who thank Bruce for being so open about these common issues that new moms are often afraid to discuss.
"It's been amazing to see the feedback from women," Bruce says. "I don't think I'm that inspiring, but a lot of women kind of felt like it is, and I just hope that other women feel that confidence, and post their baby bodies, and don't feel ashamed. These issues happen to all of us so I just hoped I could get the conversation going."
"The 10k that was more than just 6.2 miles." My post race recap up on my website. A little inside into how I got to racing 5 months post partum, my support team, the feeling of crossing a finish line again, and in true #keepinitreal Steph fashion a little anecdote towards the end. Warning may be TMI for some:) Enjoy! Link in profile.
There are still critics, but they're far outnumbered by those who thank her for showing that even Olympic-caliber athletes have stretch marks post-baby.
"Some people were like, 'Ew, this is gross, you don't need to share this,' and I'm like, 'Well, you don't need to follow me, or you don't need to look at it,' " Bruce says.
"But there's a lot of women who are like, 'Wow, this is exactly what I look like.' They think elite runners are like superhumans who roll out of bed and were born with six-pack abs, but that's not the reality. We work really hard at it."
It still looks like a hot mess but the stability and strength is coming back to my core. The big 3: bird dogs, side planks, McGill crunch performed twice a day, everyday with extreme precision. It's boring, monotonous but gets the job done. Stretch marks are here to stay! #14weekpostpartum #diastasisrecti #keepingitreal
And she's doing that every day to try and make the track and field team for the 2016 Rio Olympics.
"With the luxury of it being my job I've had ample time to do a lot of strength work and exercises," Bruce says. "But it'll be a work in progress. It's probably something that I will have to work on for years to come, but it's all part of the territory of trying to be a pro athlete and trying to have babies."