Will Vonn do the unthinkable and win Olympic gold?

Veteran skier Lindsey Vonn is an "iconic superhuman athlete" and is "risking everything" by racing with an anterior cruciate ligament injury on Sunday, says former Olympic skier Chemmy Alcott.

American Vonn has completed two impressive Winter Olympics training runs for the downhill event at Olimpia delle Tofane in Cortina, only one week after rupturing her ACL in a crash at a World Cup race in Switzerland.

Vonn, 41, clocked the third-fastest time of the day in another session disrupted by the weather, prompting speculation about what is considered to be a serious injury.

"After two training runs, Lindsey Vonn is pulling the pressure off her left leg but she is still fast," Alcott told BBC Sport.

"She is an iconic superhuman athlete and is risking everything for this. She is putting her life on the line for this moment on Sunday.

"With two training runs going well, something will be ticking saying 'I can do this'."

The second practice run came after she responded to a social media post from sports medicine doctor Brian Sutterer in which he claimed the 2010 Olympic downhill champion may have already been functioning on a torn ACL before the crash, which saw her airlifted to hospital.

"What was the state of her ACL before the crash last week?" Sutterer wrote.

"What she is doing now would not be nearly as surprising in an elite athlete whose knee was already functioning like the ACL was torn at baseline."

Vonn replied: "Lol thanks doc. My ACL was fully functioning until last Friday. Just because it seems impossible to you doesn't mean it's not possible. And yes, my ACL is 100% ruptured. Not 80% or 50%. It's 100% gone."

Sutterer suggested that "someone who had a prior tear/surgery may not be as swollen and painful with a repeat injury" and "the body has time to adapt and retrain muscles to support the knee" if the injury is "chronic".

Vonn was 1.39 seconds off the fastest time of the day in Friday's training session, which took place in difficult weather and surface conditions because the snow was softer after heavy snowfall earlier in the week.

On Saturday she improved on her time in more favourable ground conditions, completing the run in one minute 38.28 seconds, 0.37 seconds off compatriot Breezy Johnson, who clocked the fastest run, and more than six seconds faster than the first run.

"It was important to get on snow today because it's a very different run," Vonn's coach Aksel Lund Svindal said.

"The times are not that much faster, but the feeling (is very different) on the skis because now it's a solid base, meaning that all the small bumps, you don't cut through them, you feel them through your body.

"She was very calm when she came down. She didn't talk about the knee at all. And then I didn't want to ask either, because I figured that's a good sign.

"She knows she'll have to push harder tomorrow, because the rest of the girls will, and it's the Olympic downhill."

On whether Vonn is physically ready to compete, Svindal added: "Good enough to win this race, hopefully. But her mental strength, I think that's why she has won as much as she has.

"And she also has some experience now, at 41 years old. I think that's what she needs to bring out tomorrow."

Vonn remains uncertain as to whether she will compete in the super-G and team events.