Christen Wallner slaps the smooth, well-groomed flank of her chestnut mare, which is still breathing hard after a trot around the sod-filled arena.
The horse cranes its neck and nods, as if to acknowledge Wallner's reassuring pats.
Wallner tugs the reins and kicks the 9-year-old thoroughbred into gear. The horse bolts toward an obstacle, leaps and clears it by inches before pulling up to an abrupt halt.
Last month, Wallner performed the same stunt before the Duchess of York, Sarah Ferguson, in international competition. Wallner competed against more than 500 of the world's best equestrians, including Princess Anne of Great Britain.
Not bad for a teen-ager from Westlake Village on her first trip to England, the Mecca for the sport of three-day eventing.
The sport combines a series of skill tests for both horse and rider. They include: dressage--a series of compulsory movements performed in an arena; a speed and endurance phase--which includes cross-country running and obstacle jumping; and a stadium jumping test.
Three-day eventing evolved from a time when the U. S. Army used cavalry horses. The riders' skills were judged and their horses were tested for speed, stamina and courage.
Today, three-day eventing is an Olympic sport and riders compete into their 30s and 40s.
Wallner, 18, already is a veteran of the sport, having ridden for 13 years. She was one of only four riders from California and Hawaii named to the North American Young Riders Championships, a prestigious team of riders aged 16 to 21 from throughout the United States, Canada and Mexico. She developed an affinity for horses when she was 5 years old. Her devotion to horses and the countless hours she spent at the stables as a youngster earned Wallner the nickname "barn rat."
She took lessons and learned to ride on an English-style saddle because her legs were too short to fit into the stirrups of a Western-style saddle. Soon, Wallner became adept at jumping obstacles at an age when most young girls still were playing with plastic dolls.
"My horses were always there for me," she said. "They were my best friends. I was good at riding and it made me happy. I just loved the way the horses moved."
Wallner started competing at age 10 and was setting goals for herself at 12. As a teen-ager, Wallner refined her riding skills and also learned to train and groom horses.
Since graduating from Agoura High last spring, Wallner has devoted her time to training and competing.
And that devotion has paid off. Wallner recently was named the best young equestrian in California by the U. S. Combined Training Assn. Wallner was also the state's top rider at the 1987 American Continental Young Riders' Championship in South Hamilton, Mass., in August.
Wallner tied for third place in last month's international riding trials in Harrogate, England, and competed throughout England for three months against many of the world's top equestrians.
"Right now, riding means more to me than anything and I'm willing to give up everything to do it," she said. "I have to be able to if I want to make it to the Olympics."
Wallner's petite, svelte frame and blonde good looks are an advantage in a sport where a horse and rider's appearance is as important as their performance.
"It's supposed to look like the horse knows what he's doing and you're just sitting there looking pretty," she said.
In her black shadbelly coat and knee-high leather boots, Wallner has no problem looking good on a horse. Decked out in her riding attire, Wallner cuts a striking figure atop her 9-year-old mare, True Core.
But the sport involves more than just smiling at the judges. Hurdling six-foot-high obstacles at a dead gallop can be hazardous. Wallner's numerous injuries in eight years of competition attest to the risks of the sport. She has had a fractured jaw, suffered a concussion, broken wrist and had stitches in her mouth after falls.
"You know the risk is there, but you just can't think about it," Wallner said.
Wallner owns and trains three horses: True Core, an English thoroughbred named High There, and a 7-year-old thoroughbred. To be successful in three-day eventing, Wallner has to cultivate a strong rapport with her horses.
"When I buy a horse, I look for what we call 'heart,' " Wallner said. "A horse has to have heart to go the distance in these events."
Wallner hopes to ride in the Olympics in the 1990s, but she cannot count on it. It will depend on whether she has a horse trained to compete at that level.
"The Olympics are my goal, but you just don't know if you will have a horse ready that has peaked with you," Wallner said. "I can't take any shortcuts.
"It's hard sometimes. People don't always understand why you're always with your horse. But when you're riding, and the horse looks good and you look good and you know everything is going well, you'll be rewarded."