It's a moment that changes your life forever.

It was the winter of 2004 and Manchester resident Stirling Winder was a freshman field hockey player at the University of Vermont preparing for finals when a routine meeting with an athletic trainer to check out her leg turned into something much worse: she had bone cancer in her right femur and she would need a knee replacement.

As if things could get any worse, Stirling found out just a month later that her stepfather, Reynolds Moulton, was diagnosed with colon cancer.

"We both did treatments on Fridays," Winder noted. "He was an outpatient so I'd spend a night or two at home. We'd have three weekends in a row then two weekends off."

When asked her reaction to the whole situation, Winder said: "I was like yeah right, how do you know this? I'm 18, this is impossible. One of my teammates had non-Hodgkin's when she was 16 and her hair started to grow back so that was almost too close to home."

After almost a full year of chemotherapy (Dec. 2004-March 2005, April 2005-Oct. 2005), Stirling finally beat bone cancer. At the time, a normally joyful occasion was much more subdued for Winder since Moulton was not doing well at all. He ended up passing away only a year after his diagnosis because an earlier heart transplant made him weaker and the chemo wasn't as effective.

With the memory of her stepfather and in celebration of her cancer survival, she's riding in the Pan-Mass Challenge August 1 and 2. It is a two-day, 190-mile bike-a-thon that raises money for cancer care and research at the Dana Farber Cancer Institute through the Jimmy Fund.

Riders go from either Sturbridge to Provincetown or Wellesley to Provincetown which a is a slightly shorter route. They stay overnight at Mass. Maritime in Bourne before the final ride to the end of the Cape (Provincetown).

"I just had surgery a month ago, my second lung surgery," explained Winder. "I get scans every three months and the first place the cancer can reoccur is in the lungs. They took the cancerous spots out and I'm not doing anymore chemo."

Winder took four weeks off from UVM her freshman year but she returned to school during the spring semester. She was enrolled in four classes instead of the normal five but other than that, she tried to keep everything at school as normal as possible. The Governor's Academy graduate (class of '04) also somehow graduated on time in 2008 at UVM.

"I went to the field hockey practices and traveled with the team and helped with the goalies," said Winder, who was a center back that started before she received the fateful news. "My senior year, I got into eight games. I can't really run so they'd just have me take corners."

A local family that she baby-sits for was the motivation to get involved with the Pan-Mass Challenge.

"Some family friends, they gave me a living proof pin. They got me into cycling last summer, the husband and wife have done the Pan-Mass Challenge for eight or nine years."

Winder rides a TREK road bike and she's been doing training runs of 50 miles at a time, two or three times a week. With her knee replacement, she'll have to stay seated in the saddle, even uphill. She is a natural athlete though and the skills from field hockey and snowboarding (another passion) will likely carry over to her newest endeavor.

"Riding a bike is really good for my leg, it helps build more muscle because of it," she said.

An unexpected benefit of spending so much time in hospitals the last few years is that Winder discovered her true calling: she wants to be a pediatric oncology nurse practitioner. She's currently wait-listed for nursing school at Northeastern and Mass. General which are ultra-competitive.

"It's a lot easier to tell people you know how they're doing when you've gone through the same thing," she explained. "And kids have such positive attitudes."