(ABC News) -- Wearing a bright-pink helmet, Vanessa Reill flies down the dirt track on the back of a racehorse. Standing at 5 feet, 5 inches tall, she pushes forward with the horse as one powerful muscle machine.
This is her shot at being a professional jockey in the death-defying, adrenaline-pumping sport of thoroughbred racing, reaching speeds of up to 40 mph.
"I just love horses, love riding, love going fast," Reill, 22, said.
In Lexington, Ky., where horses and horse racing are part of the local fabric, Reill, originally from Norway, is a few strides away from graduation at the North American Racing Academy, the only professional jockey school in the United States.
Through the academy, aspiring jockeys learn the techniques and rules of professional race riding, as well as how to care for horses, including courses in nutrition, fitness and technology.
Aside from the jockey-training program, the academy also offers a "Horseman's Pathway" program for students aiming to be grooms, exercise riders or, ideally, trainers. But no matter what the career path, everyone does barn work, has classes and takes exams.
Over the course of the two-year program, Kentucky residents pay $150 per credit and out of state students pay $450 per credit. After 60 credits, students earn an associates degree.
This year's freshmen class has 12 aspiring jockeys, 11 of whom are women, defying the professional racing odds. Only 16 percent of licensed jockeys in the United States are female, and of the top 100 jockeys right now, only two are women.
But the young ladies to whom "Nightline" spoke at the academy were ready to man up.
"No princesses, you've got to be one of the guys," Marissa Yetter, 19, said.
Looking at the odds, only two of these women will make it to the big time, but, first, they will have to elbow out the Pennsylvania native, who, at 5-foot-3 and about 105 pounds, knows full well it's a cut-throat sport.
"You have to go into any situation being humble, but yet still being able to say, 'Hey, I'm the best. I can kick all your butts.' It's a mental kind of duel personality," Yetter said. "When we first started riding, it was basically like the movie, 'Hunger Games.'"
Although Yetter's competition at the academy was mostly veteran riders, there was one freshman who had the audacity to be a novice. At 5-foot-2 and 112 pounds, Chase Roberts, a 20-year-old from North Carolina, was ready to stand his ground against his female classmates.
"I've never ridden and now I'm here," Roberts said. "All the girls didn't intimidate me, no complaints about that. But I saw that some of them were pretty good at riding and I was like, 'Dang, they know what they're doing and I don't.'"
Although he has been accepted into the academy's elite riding program, "Nightline" was there for his first time ever on a horse.
But no experience can be a leg up at the school because novice riders don't have bad habits to break. Racing a thoroughbred requires different techniques than show jumping or dressage.
Hall of Fame rider Chris McCarron, one of the winningest jockeys of all time, founded the North American Racing Academy in 2006. Like Chase, McCarron said he came into racing without much prior experience.
"I never touched the horse until I was 16 years of age, and I was riding professionally when I was 19," he said. "[Jockeys] have the greatest ability to stay out of the horse's way to the highest degree."
That includes weighing so little that the horse barely feels you on its back.
"A horse is not going to be able to perform at its optimum peak if it's carrying 100-something pounds," McCarron said.
During the academy's selective admissions, size is considered more than riding experience. The school prefers riders weigh less than 112 pounds and body fat expectations are far more rigid than other athletes, on par with the lowest percentage of body fat necessary to even survive.
"Your typical male jockey has a body fat percentage that ranges between three and seven," McCarron said. "The girls are between eight and 12."
Compare that to body fat percentages for the average American, which is around 18 percent for men and 25 percent for women.
Reill is a gifted rider and has a slim build but, she said, she still struggles to meet the weight requirements.
"I've stopped eating as much chocolate as I used to," she said. "And just trying not to go over 1,500 calories a day."
It's that kind of pressure that can be dangerous.
"Some jockeys would order a $20 steak and 20 minutes later go into the bathroom and throw it up," Yetter said. "They call it 'flipping.'"
'Flipping' in this world is slang for bulimic behavior.
"Unfortunately, bulimia is a pretty prevalent problem amongst jockeys and taking diuretics ...," McCarron said. "It's challenging."
Jockeys will risk their health and even their lives for a shot at professional racing. It's possibly the most dangerous professional sport in the country.
"Since 1940, at least two jockeys a year … are paralyzed," McCarron said. "So it's a lot more dangerous than NASCAR or parachuting or skydiving."
There are 48 accidents each week involving jockeys, according to the Jockey's Guild, which represents thoroughbred horse racing and U.S. professional quarter horse racing jockeys.
While her mother worries about her daughter's safety, Yetter said she doesn't let the potential danger bother her.
"I fell off and had a bad concussion last summer," she said. "[But], you know, 'Get back on the horse.' You don't let it faze you."
When "Nightline" visited the school again a few months after seeing Chase Roberts' first ride, he had fallen off and injured his knee, sidelining him for a month.
"I don't want to give it up," he said. "I couldn't wait to get back on the horse that knocked me off."
The burning desire is there, but their chances of making millions while racing horses are slim. Jockeys get 10 percent of the earnings, but only if they win.
"Money doesn't really ever cross my mind," Yetter said. "Honestly, I would be happy sitting on a plot of land in a trailer and having horses around me and riding on the track every day. I would be totally content with that."
They are all here for different reasons. It's adrenaline for some. It's money for others. For most, it's nothing more than the simple love of horses.
"When you're on that horse, they're running for you," Yetter said. "You can feel that. I love it. I'm 19 years old, and I'm living my dream."
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