KRASNAYA POLYANA, Russia -- The Olympic men's downhill course begins with a descent so steep that skiers quickly reach 90 mph. A subsequent jump catapults racers almost the length of a football field.

The women's downhill features a finishing jump that hurled racers so high in the air Thursday that the first training run was halted after only three of 56 skiers tried the course.

Worried for the contestants' safety, race officials used machinery to whittle the jump into a less perilous bump at 60 mph.

"I felt like, 'You're welcome, I'll be your test dummy,' " said U.S. downhiller Laurenne Ross, one of the three women to soar off the jump when the training began. "I was definitely intimidated. You just get really high off the ground; the slope just drops off and you're still going straight, and that's the problem because you feel like you're just not going to come down."

One of the realities of putting an Olympic Games in a remote location like the mountains above Sochi is that many of the venues have not been extensively tested. The men's and women's downhill racecourses, for example, were host to one major ski racing event -- two years ago.

While it is not uncommon for a ski racing course to be adjusted during training sessions, the racers on Thursday -- the men also had a downhill training run -- were forced to study the course and survive it at the same time.

Adding to the uncertainty has been the continuing inclination to make the Winter Games dauntingly extreme. Earlier this week, Olympic officials scrambled to make changes to the slopestyle course after injuries to top snowboarders, including one who broke his collarbone in a crash.

On Thursday, one of the three women to test the course, Daniela Merighetti of Italy, said she injured her knees landing the final jump. On the men's side, only about 20 of the top 45 racers successfully negotiated all the gates as many were racing at speeds that propelled them off-course.

"The course is just unrelenting," said Travis Ganong, a 25-year-old American. "It really doesn't compare to any course we normally see. It just keeps coming at you."

The 2.2-mile-long men's downhill course, which on Sunday will require racers to descend about 3,500 feet in roughly two minutes, has a series of unnerving features that have been bestowed evocative names like the Russian Trampoline, the Toboggan, the Estonian Tube and Bears Brow.

It will have skiers soaring in the air for some of the longest distances in Olympic ski racing history, especially off the Lake Jump, so named because the only thing they can see in the distance as they approach the crest of the jump is a snow-making lake.

From that vantage point, it appears as if they will land in the water. Instead, with good balance and technique, their skis will make a jarring return to the snow about 275 feet from the jump's takeoff.

The top-end speeds of the men's downhill at the Rosa Khutor Alpine complex here will also be among the fastest for an Olympics. Only 12 years ago, 75 mph was considered a harrowing challenge for an Olympic downhiller. The Sochi games are redefining the high speed lane of a high-speed sport.

And yet, because downhill racers are inherently outlandish daredevils, the challenge of a new, untested Olympic racecourse has mostly yielded fawning admiration.

"I'm glad they didn't dumb it down or take any of the teeth out of it," said the American Bode Miller, who had the fastest training run Thursday. "Many of our World Cup courses, they have made easier. This one is tough, and you have to be willing to take the risks. It's got everything -- high-speed turns, gliding sections and really long jumps."

Miller's teammate Marco Sullivan added that the field had not actually seen the true difficulty of the men's downhill because in the training sessions every racer had been easing up -- known as standing up -- on some sections to conserve energy and assess the terrain.

"When everyone stays down and pushes the whole way," Sullivan said, "by the end your legs will be pretty smoked. And then you've still got to navigate some tough jumps at high speed."

Aksel Lund Svindal, the pre-race favorite, added: "I think the racecourse is getting better the more we ski it. You see more of the challenges, but it should be challenging."

As for the women, who do not race the downhill until next week, their Thursday training resumed after a delay of nearly two hours. The entire field was given a re-run, but Merighetti, who is hoping to compete in her third Olympics, did not take another trip down the course.

Ross did but was warned first.

"We were told to slow down before the jump so I didn't get air." said Ross, who finished 14th.