Yamamoto triumphed in the men's 500 metres, while Grevelt won the women's 500m race on the opening day of speed skating at the third Winter Youth Olympic Games.

All the talk before the event centred on the conditions at the St Moritz Speed Skating Oval as organisers were forced to reassure athletes the lake had sufficiently frozen to host safe competition.

Yamamoto and Dutch athlete Julie Berg Sjoebrend admitted after the event that the surface was far from ideal.

Skaters are used to competing on smooth, crack-free ice and today's races represented an entirely different challenge.

But Yamamoto said the "cracks" in the ice were "no problem for me" as he clinched the gold medal in a time of 36.42sec.

Nil Llop Izquierdo of Spain earned silver, 0.18 adrift of the victorious 17-year-old from Hokkaido, while bronze went to Xue Zhiwen of China in 36.67.

The Netherlands are traditionally strong in speed skating and Grevelt showed their success in the sport might continue for a while yet as she sealed the women's title in 40.57.

Grevelt finished 0.50 clear of China's Wang Jingyi in second and Yukina Yoshida of Japan took bronze in 41.16.

"I knew I had to finish under 41 seconds," the 17-year-old Dutch skater said.

"I have done in the past, so I was hoping for it, but I was still really nervous."

Sjoebrend, who languished down in 27th place, said she fell in a hole in the ice during the women's race.

"It was really hard," she said.

"I fell in a hole in the ice. 

"That was embarrassing and I was kind of afraid [afterwards]. 

"It affected my confidence a little bit, so I tried to block it out.

"But I’ve loved being here on the lake in the morning, seeing the sun come over the mountains."