Lake Mary is a scenic slice of California’s Sierra Nevada, a gorgeous blue body of water rimmed by evergreens and jagged, snow-covered granite peaks. On calm summer mornings the image of the most prominent of those peaks, 10,364-foot Crystal Crag, reflects off the lake’s surface.

It is here, at almost 9,000 feet, that Alexi Pappas is transforming into a marathoner. Every week, she churns out two-mile repeats around Lake Mary under the eyes of her coach Andrew Kastor. Pappas began training full time in July for her marathon debut in Chicago on October 7, and her program includes speed work on a track in Mammoth Lakes at more than 7,000 feet on Tuesdays, strength days at Lake Mary on Fridays and long runs on Sundays.

It’s the circuits around Lake Mary she counts as the “most educating” and hardest days. As the weeks go by, the number of reps increase. She calls it “unglamorous,” but knows it’s working. She doesn’t run great times at that altitude, but it’s the effort that counts. Even when she drops down to Mammoth Lakes, her workouts are stronger now.

Pappas, the 28-year-old former Dartmouth and Oregon track and cross country All-American who ran the 10,000 meters for Greece in the 2016 Olympics, has embraced the process. She’s relishing the chance to focus solely on preparing for Chicago in a slow-paced environment where she can hang out with her teammates, cook her meals, take naps and actually recover on recovery days in Mammoth Lakes, her home for the past year and a half.

Those increasing two-mile circuits around Lake Mary (she won’t say how many, because she doesn’t want young runners who follow her to emulate her), help provide a mental component to her training as well, she says.

“[Sometimes] I’d rather be done, but I have one more rep and the goal is just to get through it and not look at the watch,” she says. “And just by getting through that mileage you know that you’ve done a substantial amount of work.”

Photo Courtesy of Alexi Pappas

She’s so depleted after running hard at that altitude, that it makes her body feel as if it’s never red-lining when she pushes it in other runs. “You can feel like you can hold the threshold pains for a lot longer than you think you can if you just give it a chance,” she says.

She relates it to her experience in the late summer/fall of 2015 when she trained at Mammoth for about four weeks with Deena Kastor, who would set a master’s record of 2:27:47 that October at the Chicago Marathon. That same month, Pappas ran her longest race, the USATF 10 Mile Championships. At about the midpoint, she recalls having doubts about her ability to keep going hard for another five miles. But then her lessons at altitude kicked in and she stayed strong and finished third.

“I remember thinking, ‘Why don’t you try to hang in there for like three more minutes and see how you feel,’” she says. “It wasn’t such a high-stakes race that I couldn’t take a risk like that, and sure enough you find with this kind of training you can sustain a lot longer. That rough part went away and I was just able to hold that, and that was a big surprise to me. But it certainly takes believing in your training and knowing that you’re prepared to be uncomfortable for much longer than you think you are.”

After the Olympics at Rio de Janeiro two years ago, Pappas knew she wanted to move up to the marathon, with her aim to run at the 2020 Games in Tokyo for Greece (she was born in the Bay Area but has dual citizenship). Yet she waited a bit so she could go through a full marathon school with Andrew Kastor this year. Having been a pacer at Chicago and run other races in the city, she says it felt like a natural place for her debut.

Pappas has run road and track distances from 1,500 meters to the half marathon (she ran 1:21:53 in San Francisco in 2015), but says doing a marathon is like a “new sport.” Although she’s fit and confident, she’s never run 26.2 miles, so there’s an unknown. Under coach Kastor, she says she’s getting a broad education. On speed days, she and her teammates will run repeats of 400, 800 or 1,000 meters and up to a mile on the track. It’s a change of pace from other days, with more energy, music blaring out of a speaker and more focus on splits and precision.

Photo Courtesy of Alexi Pappas

On long-run days, she’s been gradually building (though again doesn’t want to give specific mileage). On one Sunday in mid-September, she was on her feet longer than she’ll be racing in Chicago. “That’s about as long as we’ll go,” she says. “It was a good mind bender to know I could be on my feet that long.”

She’s learning how to properly fuel and take fluids, how to attack the hard days and embrace recovery days so she can be at her best. She’s taking more naps, sleeping more in general and taking time for Epsom salt baths. “I’m making sure I’m showing up on those [workout] days ready and using my time wisely by coming prepared,” she says.

It’s all a learning process, a metamorphosis to marathoner. When she steps to the starting line at Chicago she’ll also be clad in the clothes of new sponsor Champion and using a new Garmin 645 to keep her pace. One thing that excites her is she’s following in the footsteps of so many terrific marathoners who have trained at Mammoth, such as Deena Kastor, Meb Keflezighi and Ryan Hall. She feels that connection when she’s doing the same workouts or running the same roads they have. Especially, when running Green Church Road, long used for tempo runs.

“You believe in the history of this place and when you’re racing, you feel like you’re prepared just like those athletes were,” she says. She doesn’t have a specific time or goal for her first marathon. Kastor has taught her to be patient, trust the process and have this race open the door to others. She has time to get better for 2020.

Pappas hasn’t done any prep races for Chicago, preferring to stay in Mammoth. But she’s running with an elite group in the Sierra and can’t wait to run with the likes of Gwen Jorgensen and Laura Thweatt in Chicago, women she admires and considers friends.

“I know how to race,” she says. “And I’m next to girls in workouts all the time, so it’s not like I’m not familiar with a crowd. I love racing, so even holding myself back from the pleasure I get from performing has been kind of fun. It’s like I’m in a little incubator and I’ll come out when I’m ready.”