During her first two Chicago marathons, Erin Chernick felt pain but kept running.

“I sort of walked/shuffled it,” she said.

She had broken bones, torn ligaments and needed surgery. She planned to take a year off.

Then her uncle got cancer. Her answer was another marathon.

“I thought of what I could do,” she said. “I could still run.”

Now, Chernick, 25, a fourth-year NU graduate student in chemistry and six-time marathon veteran, is preparing for an even greater challenge: the Ford Ironman Wisconsin Triathlon.

On Sept. 10, she will compete in the triathlon with Team 4, a group of about 30 female athletes led by professional triathlete Heather Haviland. The team will raise money for four major cancers exclusive to women: uterine, ovarian, cervical and breast.

The Ironman is 2.4 miles swimming, 112 miles biking and a marathon.

“It’s the hardest thing I’ve ever done, but also the most rewarding,” Chernick said.

The team plans to raise more than $200,000 to donate to the Medical College of Wisconsin Cancer Center, Haviland said.

“You really face your inner demons,” Chernick said of the long training hours. She talked about “hitting a wall” during training, crying and days when her body ran out of energy.

Her frequent training partner, Patrick Merle, has seen Chernick work through these demons the way she mixes chemicals in lab.

“She will feel depressed, but it won’t last because she will find a solution, her magic potion,” Merle said.

Despite losing her uncle to cancer, Chernick said she has a lot to be positive about.

When Chernick was 23, a routine test found abnormal cells, but a cone biopsy ruled out cervical cancer. She has been healthy ever since.

“I don’t know what I would do if I had cancer. That’s a whole other battle that I’m trying to conquer in my own way,” she said. “If I can get through the Ironman, I can get through a lot.”

After fracturing her pelvic bone in 2004, doctors said her days of distance running were over. The next year she safely ran the Chicago marathon “for fun.”

In a typical week, Chernick rests on Monday, but on other days she gets up at 4:45 a.m. and bikes or swims for an hour and a half. Then she goes to work, takes a 90-minute break to run or lift weights and heads back to the lab.

Chernick said a complete Ironman burns about 9,000 calories, so she snacks on energy bars and supplements all day. She said she often wakes up in the middle of the night to eat peanut butter and jelly sandwiches.

Her bottomless drive is fueled by her fight for a cure.

“I have tough mornings where I just want to sleep, but then I think about those women. Do I really want to have chemotherapy either?” she said. Her eyes welled up as she spoke of her uncle. “I watched him fight for eight months. I saw him deteriorate.

“This can’t be that bad compared to it,” she said. “It keeps you from complaining a lot.”

Reach Jen Wieczner at [email protected].