Mackinzie Pooley placed first in the first round of the national  championship for junior dressage riders on Saturday, but don't expect  her friends at Tesoro High School to know what that means.

"They're  like, 'So you race horses?'" the 15-year-old Coto de Caza girl says of  the usual comments she gets about her sport? "No, I don't, I tell them.

" 'Do you sit on them and make them look pretty?' Noooo, I don't do that either."

What  Mackinzie and her Oldenburg mare Jonkara do is often described as  gymnastics or ballet on horseback, though neither of those completely  capture this equestrian sport, which this weekend and next holds its  Olympic trials in San Juan Capistrano.

In the arena, rider and  horse perform a series of movements, demonstrating a wide range of  training, the goal of which is more or less to effortlessly move as one.

The  horse might extend its stride and seem almost to glide around the arena  at one moment, then jauntily trot in place for the next test of the  horse and rider's ability to work as one.

Watching it might seem slow and confusing at first, but stick with it and an almost a Zen-like beauty starts to emerge.

While  Mackinzie might win a national title today for riders 14 to 18 years  old, the big show at the Oaks Blenheim equestrian center today through  next weekend is the competition of 12 teams of riders and horses for  three spots on the Olympic team.

"Just being here is huge," said  Gil Merrick, managing director for dressage at the U.S. Equestrian  Federation. "If you're here, you're one of the top horse-rider teams in  the nation."

American riders have won bronze medals in the past  three Olympic Games, Merrick said. (Of the nine riders in the trials  here, four won Olympic bronze medals.) Germany and the Netherlands  typically battle for the gold and silver.

"We could get a silver  medal," Merrick said of the Olympics which for this sport will be held  in Hong Kong, not Beijing. "But the bronze isn't assured.

"There  are probably six countries including us, who are usually fighting for  the bronze. So we have to be at the top of our game."

Long a  sport more popular in Europe than in the United States, dressage  suffers in part because it's harder for newcomers to understand what is  happening in the arena, Merrick said.

"Jumping, it's easy for the  public to understand, you can see whether the fence stayed up or not,"  he said. "Dressage has more of a precise elegance to it."

The  covered tents and bleachers were only half-filled on Saturday, but by  next weekend, they will fill for the final days of the Olympic trials.  Most of those there on Saturday seemed to already have a connection to  the sport, such as Susan Walker, 18, and Emma Ransom, 15, two dressage  riders from San Diego.

"It's definitely an intricate sort of  thing," Walker said, offering a simple way to tell which of the  competitors is doing the best.

"Even for somebody who doesn't  really know what they're looking at, if it looks pretty, it's probably  being done well," she said.