After more than four months of training for about seven hours a day, with thick calluses forming on their hands, 393 martial arts students staged a visual feast of blooming flowers and waves of green grass, signaling the start of spring, at the National Stadium to kick off the opening ceremony of the 2022 Beijing Winter Olympics on Friday.

The program, titled Li Chun－the beginning of spring, the first of the 24 Chinese solar terms－was performed by students from two martial arts schools in Shandong province. Aged from 14 to 18, they wielded 9.5-meter-long flexible poles that emitted multiple colors.

"This kind of matrix performance used to be presented with banners and flags, but this time we used a new material whose flexibility and intensity can present an effect of rising and falling, such as wind blowing grass low and dandelions whirling in the wind," said Gao Zhiyi, a director of the program, who is deputy head of the music school at Shandong Normal University.

It was not easy to present the matrix with long, flexible poles, Gao said.

"It's like using pens to portray the effects made by brushes," he said. "The program, lasting around three minutes, had 200,800 moves."

The students needed to memorize complex movements for the routine, and their movements were individually choreographed, said Zang Hua, deputy principal of the Zhonghua Martial Arts School in Laizhou, Yantai, Shandong.

"The biggest challenge was to control the poles, which weigh 5 kilograms each," he said.