Yuan Xiangzhen,65,works at an express delivery company to help her son pay back the money he borrowed to pay for her medical treatment. Zhu Xiyong/China Daily

Yuan Xiangzhen's dearest wish is to play with her grandchild. Instead, the 65-year-old rushes around every day delivering parcels.

After checking the packages a second time, Yuan packs them into the woven bags she carries on her back.

"Each bag weighs about 25 kilograms, and I walk 2 kilometers to work each day and then 7 to 8 kilometers doing the deliveries," Yuan says.

In order to be able to carry the heavy bags, she has to lean forward, as if dragging a car. She walks fast and only stops when the bags fall to the ground.

"I can't take a break. Once I stop, I can't start again," she says.

No matter how many stairs she has to climb, she insists on delivering all the packages to the doors of the clients, as she is worried they might go missing otherwise and the clients complain, in which case she would have to pay a fine, which she would not be able to pay.

In fact, Yuan is working to help her son pay back the money he borrowed to pay for her medical treatment.

In 1999, Yuan's husband was diagnosed with liver cancer. Although, he died just a year later, the family still had to take out a heavy loan to pay for his medical bills. A few years later, Yuan was diagnosed with heart disease and diabetes. Despite her injections of insulin three times a day, she was unable to control her illness and in 2011 she was hospitalized twice. Her son Peng Shuang, who works at the same express delivery company as his mother, had to borrow a hefty loan from a usurer.

"As a son, I feel really guilty that my mother has to run around," Peng Shuang says. "But my mother always wanted to help me when she could, so that we could pay off the debt."