LANZHOU, China, May 13 (Xinhua) -- IN a plaza in Lanzhou, northwest China's Gansu Province, 10-year-old Wang Wending is briskly roller skating through a row of cones placed in front of him. "Hang on! Only two left!" Ni Juan shouts at him, guiding him through the plastic obstacles.

Ni Juan, 26, has been a roller-skating coach for several years. She and her husband run a club teaching children to roller skate.

Ni Juan started learning roller-skating when she was in college. "I saw other students doing it, and they looked really cool. So I decided to learn it myself," Ni said.

During her training, Ni met another student named Hou Minghua. More experienced in the sport, Hou taught Ni to do artistic roller skating, and advised her to be a coach in a club when she mastered the skating skills.

After years of spending time roller skating together, they fell in love. In 2016, they got married after Ni graduated from college and started their own business two years later. They opened artistic and speed roller skating classes for kids, and were welcomed by huge numbers of children.

All things are difficult before they are easy. Lanzhou gets quite cold in autumn and winter, and it also snows a lot, which makes it hard for children to take part in outdoor activities.

"Students come, they learn, and they give up midway," said Ni.

The declining number of students frustrates Hou, but Ni is still quite confident. "We managed to make money from our hobby, and made friends with about 100 kids every year. It is worth hanging on for."

Encouraged by his wife, Hou drew up a plan: during spring and summer, they focus on training students; and when the low season comes, they attend training courses and lectures to improve their own skills.

Wang Dingwen is their favorite student. At the very beginning of his training, he could barely lift his feet with roller-skating shoes. After years of painstaking practice, he is now the pride of Ni and Hou. He has won many prizes in the different levels of roller-skating competitions.

"When he was just a little boy, I sent him to the couple to learn roller skates. Back then, they were still college students. They not only trained him, but also took care of my son very well. I trust them a lot," Wang's mother said.

Guo Xuanyin, nine, is a four-year skater. She was sent to learn it because she was too thin and weak. "We sent her to attend the training to improve her physical health, and it really makes a difference," her father said.

The girl is no longer weak. Now she can perform a lot of difficult moves in roller-skating shoes. To her, roller-skating is not just a hobby, but a specialty as well.

In April this year, the couple cooperated with an English training school, offering 14 free lessons each year for students here. "We hope more children take interest in roller-skating and have fun with it," said Hou.