LHASA－On a mountain pass at an altitude of more than 4,400 meters, a spoke on Hou Weiyu's front wheel was broken by a flying stone. He got off the bicycle, checked its condition and got on it again, heading to Lhasa, the capital of Southwest China's Tibet autonomous region.

Hou, 52, was among the 10 amateur contestants in a field cycling race that stretches more than 2,000 kilometers along the highway between Sichuan province and Tibet.

On May 21, they set off from the city of Ya'an and rode across 14 high mountains, including two exceeding 5,000 meters above sea level.

Despite a minor accident, Hou spent five days 17 hours and 26 minutes competing in the race.

"Unlike in the flat plain area, riding on the plateau requires much more energy, which is far more challenging," says Hou, who works for a cement supplier in Beijing.

June 3 marked World Bicycle Day. Bicycles used to be a luxury for many Chinese families in the 1960s and 1970s. With the rapid economic and social development of the country, bikes have become a common household property. As more Chinese own private cars, cycling has become more of a fashionable sport than a means of transportation.

The Sichuan-Tibet Highway is considered to be an ultimate challenge by cyclists because of its beautiful scenery, complicated landscape and high altitudes, attracting an increasing number of amateur riders in China.

For the event, the contestants were selected through a series of qualification competitions, such as a plateau race and an endurance race.

For safety reasons, the organizers arranged vehicles loaded with volunteers and first-aid equipment to follow the riders. However, the riders would not be offered help unless they quit the race, says Jiang Wukai, founder of the race and also an amateur cyclist, adding that it is the ninth year the race has been held.

About 19 hours after Hou reached the finish line at the foot of Potala Palace, a landmark building in Lhasa, Zhang Jingzhong from Shenzhen, Guangdong province, arrived, to claim second place.

Zhang, an entrepreneur engaged in beef meatball production and sales, previously entered the race twice, but both attempts ended in failure.

"I had to quit because of my severe high altitude sickness the first time. As for the second time, I fell and hurt my forehead when riding downhill," he says while taking off his helmet, revealing a scar on the forehead.

In a bid to conquer the altitude sickness, Zhang arrived in Sichuan half a month earlier this time and spent five days in a 4,000-meter-high area to adapt himself to the high-altitude environment.

During the race, he encountered heavy snow on a mountain and had to trek for some two kilometers while carrying the bike on his shoulder.

"Despite all the difficulties, I finally realized this ultimate dream. I think that's what an extreme challenge is all about," he says.

The riders who challenged their physical limits also won respect from people of different ethnic groups along the route.

Zeng Zhu, who claimed eighth place, recalls that he lost his gloves halfway and went to a roadside store to buy a new pair.

"When the Tibetan boss saw me in my race suit, he refused to accept any money and gave me a thumbs-up," says Zeng, a dietitian trainer from Shenzhen.

Although in his 50s, the champion Hou has planned to ride for a few more years.

"My next goal is to attend the 1,200-km PBP (Paris-Brest-Paris) event," he says.