Rea Kolbl loves to run. A lot. And usually alone, on long, steep mountain trail runs in her adopted home of Boulder, Colorado.

“I can just get lost, in a good way,” says the 27-year-old elite obstacle course racer and Spartan Pro Team member. “When I am on trails, I stop thinking about everything else. Running steep trails like the ones in Boulder can be hard, but it’s the good kind of hard where you can zone out everything else.”

Related: 6 Most Scenic Trail Runs in North America

Running 90 Miles a Week

When she’s in prime form, Rea Kolbl, a native of Slovenia, runs her five-foot-four, rock-solid physique through close to 100 miles a week—more than most elite obstacle course racers and as much as some professional distance runners. But these aren’t flat, boring miles on paved roads or concrete bike paths.

On most mornings, you can find her hammering up and down the rocky trails in the foothills and mountains that make up Boulder’s western boundary—Mount Sanitas (6,843 feet), Flagstaff Mountain (6,983 feet), Green Mountain (8,150 feet), and Bear Peak (8,459 feet)—or tackling the arduous Skyline Traverse run that incorporates all of those peaks in one massive 20-mile run. She’s also started to zip up some of Colorado’s 14,000-foot peaks, starting with Quandary Peak (14,265 feet) and Pikes Peak (14,114 feet).

Training in the Mountains

It makes sense, though. As much as OCR requires strength, quickness, and agility, it’s inherently an aerobic sport just like trail running. But, honestly, she runs for the joy as much as she does for the training effects.

“A lot of the time, I get to places I wouldn’t get to otherwise,” says Kolbl, who moved to Boulder from the San Francisco Bay Area in 2017 to take advantage of the renowned trail system and mountains. “When I’m out there, it’s usually only me and the trails and the summits and the gorgeous views when you get to the top. It’s peaceful and hard and wonderful at the same time.”

Kolbl runs almost every day, typically starting her mornings with a 10- to 14-mile run on those steep mountain trails, although she admits she does mix in some flatter, rolling trails to give her legs a break. After most runs—which might last from 90 minutes to more than 2½ hours—she’ll throw in a couple of rounds of pull-ups and drills to work on her balance, stability, and core strength. One day a week, she’ll spend 30 minutes dragging a tire.

Related: 7 Great Trail Running Tips for Beginners

Needless to say, she considers her aerobic engine, uphill running ability, and strong legs her biggest assets as an OCR competitor. “I think more trail runners should try OCR,” she says. “You already have strong legs that can get you through the course and help you carry heavy buckets up the hills. I manage to catch and pass a lot of competitors going up hills. The grip strength and upper body strength were a challenge for me originally. So right after my training runs, I started doing as many pull-ups as I could do. And that helped a lot.”

Rea Kolbl Loses Her Edge

As a kid in Slovenia, Kolbl was a talented gymnast on her country’s national team until she was 17. After that, she turned to track and field and tried pole vault. But by that point, she was burned out on competition. She says she took a hiatus from fitness and lost her edge. “After gymnastics, I gained a lot of weight. I was breaking poles more than I was jumping with poles,” she says sheepishly. “I felt it was my life mission to eat all of the ice cream that I didn’t have when I was little.”

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#transformationthursday when carrying a sandbag up a hill is easier than what it used to be to carry just me. ••• After gymnastics I went through a rough patch of gaining a lot of weight and living unhealthy. I ate sweets every day but it only made me bitter. It was hard to move and being active wasn't fun. It took years to get my fitness back, but the way I feel today, I wouldn't trade it for all the sugar in the world. ••• If you're struggling with eating healthy and being active, make small goals and do just one more thing today than what you did yesterday. Whenever I gave myself big goals I would stick with those for maybe a day or two, but always got overwhelmed and fell back on my old habits. Eventually I realized it will take time, and taking it one day at a time, eventually these small steps became my new life. #healthylifestyle #smallsteps #likeagirl #betterme

A post shared by Rea Kolbl (@reakolbl) on May 24, 2018 at 2:30pm PDT

Coming Back Stronger

She moved to the U.S. at age 19 to attend the University of California and took up running to get fit again. Long before she discovered OCR, she started to become a pretty good trail runner. She ran races ranging from 25K to 50 miles, typically placing among the top women. And a few times beating all of the men and winning outright.

It turns out her combination of aerobic strength, agility, and tenacity were the perfect mix for obstacle course racing. She participated in her first 13-mile Spartan Beast in Monterey, California in 2013 and did pretty well competing in the open category. Although she had a blast, it would be three more years until she summoned the courage to compete in Elite. Once she did in 2016, she placed fifth among the elites in the Beast at the same Monterey venue. Her OCR career immediately skyrocketed.

Since then she’s racked up numerous podium finishes. She won the 2017 World’s Toughest Mudder. Took first in Spartan’s U.S. and World Elite Point Series. And second in the Obstacle Course Racing World Championship 15K event. Although she was slowed in 2018 by a foot injury, she racked up six wins (two Tough Mudder events and four Spartan races), making her a serious contender for the 2018 Spartan World Championship in Lake Tahoe.

Still the Trail-Running Queen

Despite her love for running, her OCR success more or less ended her trail racing career. Until she took second at Broken Arrow Skyrace—a 52K race near Lake Tahoe on similar terrain as the Spartan Worlds.

“That was a surprise. I didn’t think I’d be able to keep up with all of those skinny mountain runners. But when you don’t have to carry heavy buckets, you can be a little faster on the trails,” said Kolbl. “I was thinking that course would be great training because it’s a two-lap, 31-mile race. It would make Spartan Worlds seem easier because it’s about half that distance on the same terrain.”

Rea Kolbl Looks to the Future

Kolbl earned bachelor’s degrees in physics and astrophysics from UC Berkeley. And a master’s degree in science and engineering from Stanford. But for now, she’s putting any vocation on hold as she keeps running down her dreams in OCR.

Keep an eye on her in the next Spartan World Championship. Will she podium? We'll end this article with her advice to anyone who's considering their first Spartan race:

“My advice for runners doing their first race would be to not worry about being 100 percent ready for it,” she says. “Just sign up and do it and see where you are lacking. That’s the best way to see where you need to train for the next race. It’s sometimes hard to figure out where to start your training. So do a race, see how it goes and where you struggle. And then train for that before your next race.”

Run like Rea Kolbl with one of her favorite workouts: A race simulation from Yancy Camp.

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