By Nick Mulvenney
ROSA KHUTOR, Russia (Reuters) - Two of the first six riders in Sunday's opening snowboard cross seeding run fell heavily and were taken away on stretchers, a day after Russian freestyle skier Maria Komissarova was seriously injured on the same course.
Komissarova underwent more than six hours of spinal surgery at Krasnaya Polyana Hospital Number 8 on Saturday after breaking her back in a crash during training for the women's ski cross at the Rosa Khutor Extreme Park.
The course for the snowboarding event has some different sections but many of the same jumps, twists and turns.
Norwegian Helene Olafsen was the first rider out and after one jump turned 180 degrees before landing on her back and shoulder.
There was a lengthy delay as she was attended to on the course but she appeared to be conscious as she was stretchered off the slope.
American Jacqueline Hernandez, who went out sixth, was the second faller, hitting the slope with a thud as she tried to land backwards and appearing to lose consciousness as she smashed her head into the snow.
Again there was a delay as she received medical treatment but again she had recovered consciousness before she was taken away on the stretcher.
The U.S. team later said Hernandez had been treated in the medical tent where they ascertained she had suffered a concussion. She was withdrawn from the competition.
The International Olympic Committee said the courses had been approved by the federations, who are responsible for their respective fields of play.
"I know they are very happy with it," IOC spokesman Mark Adams told reporters.
He said he had just been informed of the two incidents in the snowboarding competition but said there was "no huge cause for concern," and they were unrelated to the Komissarova accident.
"The accident was in an individual practice. She (Komissarova) was actually in training by herself when the accident happened. So it is not actually the format or the course that is necessarily the problem.
"They (courses) did not appear to have any difference from Vancouver (2010 Olympics). The athletes are happy with the course," he said.
Despite the two incidents, defending champion Maelle Ricker echoed Adams' view that there was nothing wrong with the course.
"It's actually just getting nicer and nicer throughout the day, getting softer and it's going be perfect for the afternoon," said the Canadian.
After a second seedings run completes the field of 24 qualifiers, the boarders will run in a series of knockout races to decide the medals later on Sunday.
(Additional reporting by Karolos Grohmann, Editing by Ossian Shine/Peter Rutherford)