Yan (center) was the first blind runner from the Chinese mainland to finish the Boston Marathon. Cheng Yi (left) and Cai Shiyin (right) are volunteers from the nonprofit Running in the Dark.[Photo provided to China Daily]

When he started training with the help of his sister and parents, he could run only for 2 or 3 km at a time.

But soon he improved so much that his sister had to ride a bike to stay ahead of him and guide him during training.

It took him just four months to be ready for his first full marathon.

Yan attributes his quick progress to the physical strength gained through a daily exercise regimen that included more than 10,000 jump rope repetitions.

Since then, he has only upped his pace.

According to Yan, ideally, he would like to run 200 km per month.

"I feel uncomfortable if I do not run for two days in a row," says Yan.

But his training is subject to the availability of running guides. And it is becoming harder for Yan to find running guides for marathons now, because there are few guides who can run faster than him.

His guides typically need to be in better physical condition than him and have faster personal times than he does.

Shu Hao, an experienced marathon runner, was one of Yan's running guides for this year's Beijing Marathon.

Speaking of how they paired up for the Beijing event, Shu says: "I first met Yan during the Boston Marathon (in April)."