Going into his first marathon, Yangzi Jiang didn’t want to know too much about the route through Philadelphia.

“I did get a text from a friend last night who did a race in Philly a couple years ago. There’s a pretty hilly part in Fairmount Park,” he said in an interview Friday. “I just want to have a fresh eye, a fresh mindset.”

Embracing new challenges is something Jiang has been doing since he was a teenager, when treatment for osteosarcoma, a kind of bone cancer, required that his right leg be amputated below the knee in 2010. The surgery resulted in his becoming more athletic than he had been before. He wrestled in high school, and as an adult embraced kayaking, rock climbing, and backpacking.

By Sunday afternoon, Jiang was hurting and exhausted, but he had completed his first marathon. He hoped before the race that he might run the 26.2 miles in five hours, a time good enough to qualify for the Boston Marathon’s Para Athletics Division. His final time: 4 hours, 42 minutes, 52 seconds.

“It went great,” he said. “I was never in this much pain, but spiritually I feel great.”

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Jiang was among 24,000 runners participating in the Philadelphia Marathon on Sunday. In its 27th year, the event has involved as many as 30,000 participants. The smaller pool of runners this year reflects precautions related to COVID-19. Last year, the pandemic shut down the event entirely.

For Jiang, the pandemic instilled a passion for running.

“Quarantine, COVID last year helped me rethink really better what’s important to me, what means a lot to me,” he said. “I really enjoyed running this time. I’m not doing this for a high school team. I’m just really doing this for myself.”

Finishing a marathon became a goal, he said, because of how difficult he knew it would be.

“I think running is something that I feel uncomfortable with,” said Jiang, 26. “Marathons are a significant challenge that can help me to conquer this fear.”

Training for the marathon has taken two months, Jiang said, and in the weeks preceding the race he typically ran five mornings a week in Charlotte, N.C., where he works from home as a software engineer. Participating this weekend also meant finding the right gear.

Jiang tried running in high school, he said, and received a running blade prosthetic his senior year, but the fit wasn’t exactly right.

Running with a prosthetic limb requires a particularly tight fit, Jiang said. If the socket, which fits on his leg and connects to the prosthetic, doesn’t tightly align with his body, an activity such as running can become painful, even scarring, after just a half-hour. He discovered how bad it can be after he used his old blade, which didn’t fit properly, to run about two years ago.

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“After my 5K race two years ago I had minor bone bruises, some blisters,” he said. “I had to be on crutches for three weeks afterward.”

Getting a custom-made socket a year and a half ago has helped, and he uses a vacuum system to ensure a secure attachment between his leg and the socket. Even with that, though, changes in the shape of his stump over the course of Sunday’s race meant the socket didn’t keep a perfect fit. Three times he had to stop to remove the prosthetic and reattach it, and twice more he stopped to adjust it. During the run, sweat pooled inside it and needed to be poured out, and a lactic acid buildup and problems with blood circulation between miles 22 and 23 required a stop and some worry.

“I just couldn’t move my leg for about two minutes,” Jiang said.

He is in the process of getting a new socket that can shift its shape to match his body over the course of a race.

He wanted to participate in the Philadelphia Marathon, he said, because of the importance of the city in his youth and recovery from cancer. Jiang’s parents came from China first to Houston, then to Philadelphia, to seek the best treatment for his cancer. After the surgery and six months of chemotherapy at Children’s Hospital of Philadelphia, Jiang stayed in the United States and attended Delaware County Christian School in Newtown Square. He graduated from Davidson College, in North Carolina, in 2019.

He raised $1,300 for the American Association for Cancer Research, the race’s sponsor. The organization had 268 people participating in events this weekend, which also included 8K and half-marathon runs, who raised $388,699 from 7,000 donors, said Mitch Stoller, AACR’s chief philanthropic officer.

“People that are honoring their moms, their dads, and their family members,” Stoller said. “I think that’s what it’s about. It’s about people wanting to give back and fund our work.”

This weekend marks the first time Jiang has raised money for cancer research, he said.

“I’ve been thinking about how to give back to people who have gone through cancer, to families that have cancer patients,” he said. “This is something that maybe I don’t really have to become a doctor or so to try to do things like this, doing something that’s challenging and also to raise money for cancer research.”

Whether the Boston Marathon is in his future was a secondary concern Sunday afternoon. Jiang longed for a cold bath, he said, and some food.

“Right now I’m concentrating on how much pain I’m in,” he said. “If you ask me in a week, I’d probably say yes, I’d do it again.”