(CNN) -- Over 30,000 people joined this year's Beijing Marathon.
Some ran on Saturday to compete and win lucrative prize money. Others ran for fun with colleagues, friends and family.
This year, 52 Chinese catholic nuns ran for charity.
The jolly group of women came in jogging pants and whiteT-shirts emblazoned with the logo, Great Wall Appeal.org.
Nuns participating in a major public event are an unusual sight in China. Religion here is still state-controlled and activities of charity groups and non-government organizations (NGO) are regulated. Catholic figures prefer to keep a low profile.
Sister Tian Wenjiao ran a 9.8-kilometer stretch, or five miles, of the race to raise donations for the Langfang Sacred Heart Care Group, a charity group that serves scores of needy farmers in Yongqing County in China's Hebei province. In a cramped, three-room apartment, the charity cares for orphans of farmers who have died of AIDS.
She helps children like Lin Xiaoxue, 12, who lived with her grand-parents after her parents died of AIDS four years ago. No school accepted her because she, too, is HIV positive.
The orphans, Tian says, remain psychologically fragile. "We want them treated with respect and dignity so that they can have confidence to live."
Like many poor farmers in north China, their parents got contaminated with AIDS after selling blood to unscrupulous "blood devils" who used unsanitary methods that contaminated and killed countless donors.
Some former donors have survived -- barely.
They have little income and are hobbled by physical disabilities caused by the disease. "They are also facing social discrimination," Tian tells CNN.
"A lot of them have had to lie to their neighbors and say they have hepatitis."
Cui Guilin, 47, is one of them. He and his wife are living with AIDS. Although they receive government-subsidized medicine to keep their illness in check, they have remained relatively poor.
Sister Tian's charity is helping farmers like Cui to become more self-reliant. Last year, the group gave him 2,500 yuan as seed money to raise goats, the extra income meant to help Cui boost his standard of living, health and self-esteem. Cui's herd has multiplied from two to 16 in one year.
"A few months after we give them the seed money, they give back half of it, which we then use to help others," Tian said.
Tian, 37, is a graduate of psychology and theology and is good with children. She is not the athletic type, and she has had heart ailment, but for weeks before pledging to run 9.8 km (5 miles) in the Beijing marathon, she woke up at 5 a.m. daily to work out and run.
"I'm running for these children because they need a lot of attention and care," she said.
After crossing the 9.8 km finish line, Sister Tian said she was uplifted by the experience. "I had fun running," she said. "Next time I think I can run a half marathon."