KRASNAYA POLYANA, Russia (AP) — Mark Caldwell thought his daughter was joking. Then he heard the sobs.

When Ashley Caldwell called her father in December 2012 and to tell him she had just torn the ACL in her left knee — nearly a year to the day after doing the same thing to her right knee — it was all he could do to hold it together.

Yet he knew better than to approach the budding American aerialist about whether she might consider doing something else with her life, even as she underwent her second major reconstructive surgery only months after her 18th birthday.

"It's her decision," Mark Caldwell said. "It's been kind of her decision since she was 14. We've had an encouraging part. It's what she wants to do and she's really driven."

She's hardly alone.

For nearly every athlete who dons a bib at Rosa Khutor Extreme Park in Sochi, there is a tale of injury, rehabilitation and the long and often lonely road back to competition.

"We've all gone through the six-month injury or longer," men's slopestyle skiing gold medalist Joss Christensen said. "You just hope you've got to recover the best you can. It's almost like a wake-up call at least."

For Christensen, it was microfracture surgery on his knee in 2012. He spent three years trying to ride through the pain before succumbing to the reality something needed to be done. Less than 24 months later, the 22-year-old from Park City, Utah, led just the third American podium sweep in the history of the Winter Games.

It would be easy to call his triumph validation for the decision to press forward. Only that's not it. The lure of most of the sports — from halfpipe snowboarding to aerials to skicross — isn't the money, maybe because there isn't much to go around even for those who break through on the biggest stage. For every Shaun White — who is an empire unto himself — there are dozens who have to find work on the side just to keep the dream alive.

And yet they continue on, unable or unwilling to let go.

Blame it on the unmatchable surge that comes when they strap on their boots and point their board or their skis down the mountain.

American snowboardcross racer Nick Baumgartner sustained the first concussion of his career last fall. He was knocked out for several minutes, and then took a few weeks off before doctors cleared him to return. Faced with the prospect of riding alongside five other racers down a series of jumps and turns that would be hard enough to conquer alone, Baumgartner can hardly contain his joy at the challenge he'll face when the men's event begins on Monday.

"If it's dangerous and scary and I overcome it and I do well, that's what I'm looking for: that adrenaline, that rush," he said. "It's the reason I do it. So add more people, make it even scarier, because that's what I'm here for. I want to have some fun with it and enjoy it."

Even if the joy can take its toll on those closest to you.

Australian aerials star Lydia Lassila shredded the ACL in her left knee eight months before the 2006 games in Turin. She opted for surgery in which the ACL was repaired with part of an Achilles tendon from a cadaver. The procedure sped up the rehab process and there she was on the hill in Italy when disaster struck again.

The agonizing screams as she smashed into the snow — her knee blown out for a second time — were so stomach-churning, her parents vowed never to watch her in person again. They were back home in Australia when she won gold in Vancouver four years ago and nowhere in sight on Friday night when she earned bronze. When an Australian TV station broadcast a "blooper reel" of sorts back to her home country a few days before competition, Lassila chastised the reporter for scaring her mother.

Not that it stopped her from flinging herself down a hill at 35 mph and off a ramp five stories into the air on Friday night. Lassila packed four twists inside three flips in the span of three seconds in her final jump, just moments after watching China's Li Nina brutally land on her shoulder and lay motionless on the slope before walking off under her own power.

Lassila saw the wreck but didn't bat an eye. Rough landings have become so commonplace, whether it's the aerials hill or the slopestyle course or the halfpipe, the athletes have become inured to it.

At some point or another, the big one comes for them all.

It's why Caldwell, who came in 10th in women's aerials on Friday night, didn't freak out when she ripped up her right ACL in the fall of 2011.

"I was like, 'Aww, that's my one and I'm done,'" she said.

It wasn't. Once the tears and the feeling of being "gypped" subsided after the second tear, she went through the whole process again. If anything, it was easier because she knew what to expect.

Now a two-time Olympian before she's old enough legally drink in the U.S., Caldwell has no signs of slowing down even though she realizes disaster is one awkward landing away.

"It's OK to be scared," Caldwell said. "You just have to trust yourself and you overcome that fear pretty easily and you understand that's just the nature of what we do."