By Stuart Hughes
Skateboarder Garry Moore shows off his skills
Snowboarder Amy Purdy accelerates to 40mph as she carves down a slope, jockeying for position alongside her rival riders.
As she launches into a jump and flies into the air, the crowd below cheering Amy on has no inkling that she is attached to her board by two artificial legs.
The fact that Las Vegas-born Purdy, 26, is even alive let alone taking part in a snowboarding competition is something of a medical miracle.
Seven years ago, she suffered multiple organ failure and massive haemorrhaging caused by bacterial meningitis.
She spent more than three weeks in a coma, underwent more than 30 blood transfusions and lost both her legs below the knee.
Doctors put her chances of survival at less than two percent.
During the long months of recovery, Amy focused on a single goal - getting back on her snowboard.
"The whole time I was in hospital all I wanted to do was to snowboard again but I didn't really know how I was going to do it," she told BBC Sport.
Purdy soon found that the prosthetic legs she used for walking weren't suitable for snowboarding and began searching for alternatives.
"I e-mailed ski schools and prosthetics manufacturers but no-one seemed to know of any other adaptive snowboarders," she says.
"I just couldn't believe I was the only person with prosthetic legs who wanted to snowboard."
Encouraged by her able-bodied partner Daniel Gale, Purdy eventually made contact with an informal network of amputee snowboarders with whom she was able to share tips and techniques.
Within days of receiving a pair of specially designed prosthetic legs she was back on the slopes, taking part in a snowboarding competition.
Her experience highlighted the need for an organisation dedicated to promoting extreme sports within the disabled community.
Last year she and Gale founded a non-profit organisation, Adaptive Action Sports (AAS).
As well as organising training camps and courses, AAS also provides grants to enable disabled athletes to buy adapted sports equipment.
AAS has already helped dozens of people with disabilities take part in a range of high-adrenaline sports, from skateboarding and surfing to mountaineering and kayaking.
Adaptive Action Sports is now preparing for its biggest showcase yet - the United States of America Snowboard Association National Championships at Truckee, California.
More than 1300 athletes will gather at Lake Tahoe from 25 March for the world's largest snowboarding event, and a team of amputee riders has been invited along to show off their skills.
"Our main aim is to get out there, have some fun and show what adaptive athletes are capable of," says Gale.
Amputee snowboarder Thayne Mahler takes to the slopes
"Every day there's a different competition and at the end of each day our riders will get to go out in front of hundreds of people and show what they're about."
As Purdy and her fellow athletes push the boundaries of disability sport, prosthetics manufacturers are rising to the technological challenge they have set.
"We gave a skateboarding demonstration at an industry convention and everyone realised what we'd achieved on our own, without any help from anyone," she says.
"Prosthetics companies are finally starting to see the potential in what we're doing.
"One company in particular is trying to develop an artificial limb aimed towards action sports athletes.
"You could say we led the way - and now the rest of the world is trying to catch up!"