Tim Dowd knew going in that Erin Keogh, the best female high school distance runner this country has ever had, was not going to like what he was about to tell her.

It was unbearable outside, at least 90 degrees. The Langley High School track, a deep green, sun-absorbing asphalt oval placed in the middle of a valley of heat, was torrid to the touch. The air was as still as could be. Bumblebees were buzzing. This was not going to be a pleasant hour for any runner, even one as good as Keogh.

Dowd sent Keogh on her way by telling her he wanted her to run half a mile, or two times around the track. Off she went, her legs and arms pumping in spindly unison with three other teammates' arms and legs. Dowd ran with them for the first lap, then stopped and let them go on by themselves.

"She's not going to like this," Dowd said, rubbing his hands together, definitely liking this. "I've never done this before, but I think it will work. I want her to think she's killing herself, running half a mile, and then, when she's almost done, I'm going to make her run another lap. I want to prove to her she can really run even when she's dead tired."

As Keogh churned through the final turn toward what she thought was the finish line, breathing heavily, Dowd ran toward her and stayed at her side.

"Hey, Erin," he said softly, hoping to minimize any potential resistance. "I want you to run another quarter."

"No. I can't." Keogh was spurting out the words between breaths without breaking stride. "No. I can't."

"I knew you'd be mad," Dowd said, still at her side, running as hard as she was. "But I want you to run tired. This will be good for you."

Dowd got his way. Despite her protestations, Keogh said later she never even considered stopping. The two of them, coach and pupil, crossed what would have been the finish line and kept on going around the track one more time, tormentor and tormentee, partners in pain.

Keogh finished ahead of Dowd in a fine 1,200-meter time of 3 minutes 47 seconds. Hands on hips, doubled over to catch her breath, Keogh glared at Dowd. She was breathing too hard to form words.

"There was no other way to get you to run tired," he said. "If I told you you were going to run three laps, you would have paced yourself. I just wanted to show you what you could do."

This is nothing new. The last year or so, Keogh's No. 1 goal has been to outperform herself, because she is just about the only competition she has left. Less than five weeks from her 18th birthday, Keogh ran in her last high school track meet May 23 at the Virginia AAA championships in Newport News, where she won the 3,200 meters for the third consecutive year.

She will leave for the University of Texas as the holder of national high school records in four of the five distances she runs: the indoor 3,000 and 3,200 and outdoor 3,200 and 5,000. The record for the outdoor 3,000 she doesn't have, but she rarely runs that distance and no one seems to worry about it, anyway. Missing one national record in five does not alter the fact that no woman at her age has done what Keogh has done.

At the indoor regionals at George Mason University in February, Keogh became the first high school girl to break 10 minutes in the 3,200 meters.

"Eve didn't even do it," Dowd said, laughing. "No high school girl had done it -- until Erin did. She proved then that she's the best distance runner there's ever been in high school."

Her time was 9:57.83, more than 21 seconds better than she ran a year ago in the same meet. She set both the 3,000 (9:21.41) and 3,200 records in that race. Unsurprisingly, Track and Field News named her the high school female athlete of the year.

But track is just half of her story. Keogh runs cross country, too. Runs it -- and owns it. She has run seven major courses in the nation, and holds the high school girls course record on six of them. She is the only girl to win consecutive national titles in the Kinney cross country championships in San Diego. Her time of 16:43.8 in December 1985 over the hilly, 5,000-meter (3.1-mile) course was one-tenth of a second off the course record and, in that race, she had no one pushing her. She beat her closest rival by 40 seconds. There is little doubt that the record would have fallen had she been tested.

If she were in college right now, her times would put her in the top 10 in the NCAA. She already is answering questions about the 1988 Summer Olympics, although those queries may be a bit premature because the best women distance runners in the world peak in their mid- to late-20s. No matter. As a distance runner who gets better as the race goes longer, Keogh unwittingly has sprinted ahead in real life.

"Am I surprised?" she said the other day. "No. I never really think of what I've done. I guess it just pays to be devoted to something. I guess I'm pretty dedicated to what I do. I like running so much, it's worth everything I do for it."Olympics in the Future

For Keogh, the Olympics are like writing on a clean slate. Because shorter distances are not her strong point, it's likely she will run ever longer races as she gets older. But she has little experience at them, because no high school race is longer than two miles. She has run just one 10,000-meter race -- and that years ago in a throwaway event -- but that's the distance Keogh might eventually run in college and in the Olympics.

"I hate it when people ask me about the Olympics," she said. "I make immediate goals, not like five years down the road."

Said Dowd: "Her goal for the 1988 Olympics would be to make the United States Olympic trials. She has a real good shot at making the Olympic trials. The Olympics are a long shot. She first has to make it on the national scene."

The Olympics of 1992 seem more likely to be Keogh's first, if she maintains her present pace. But who can figure out where a 17-year-old is headed? As driven as Keogh is as a runner, she seems distracted and impatient -- normal, in other words -- as a high school senior.

One soon comes to realize she is more uncommon as a runner than she is as a person. For one, she doesn't like being asked about herself. Her favorite answers to questions are shrugging or fiddling with her shoelaces. Hers is a self-consciousness born from a reluctance to talk about herself as well as an intensely private view of what she does.

"She doesn't like attention," Dowd explained. "She hasn't led a normal life as far as being a high school student goes. It's hard for your whole junior and senior year to be expected not only to win a race, but to be expected to set a national record. That's unusual for a kid. She'd rather be left alone."

"The personality required for success in this sport might not be the same kind of personality that lends itself to verbosity or chattering," said Erin's mother, Amber Keogh, a jogger who got her daughter involved in recreational running in McLean seven years ago.

Dowd first noticed Keogh running in the neighborhoods near Langley High, "bopping around with her Walkman like all the kids who were running." He said there was nothing remarkable about her then.

"A lot of girls were as good as she was. It's not like she is some unbelievable mutant. But I soon realized that no one was as devoted to running and as consistent a young runner as she was. That makes her what she is. She is compulsive in education, she is compulsive in running. When she practices, I have to make sure she doesn't do more than she is supposed to do."

Her mother remembers that Erin began to show "potential" at age 11 or 12, but it was no overnight transformation. "We had her in local races, AAU events. She just blossomed and began to do well. It became apparent to us she was quite a talent, but it was not a surprise. She is intense. Winning obviously means a lot to her. Also, she just likes to do it," Amber Keogh said.Built to Run

Erin Keogh has more than a runner's mind; she was built to run. Her body, which is just 3 1/2 percent fat, according to her coach, punches through the air, offering very little resistance. She is 5 feet 7 and weighs 104 pounds, although she'd rather not discuss the weight part. It's only a matter of time before she begins to fill out, Dowd is convinced, but until she does, her gray Nikes look like boxes attached to her long, pale legs.

Keogh is a participant in perhaps the most individual of all sports, yet what she likes most about running, she says, is being part of a team.

"I like cross country most of all because we're running all together," she said. "I like being part of a group. Individually, I guess I put a lot of pressure on myself. I just have to remember I'm running for myself, not others."

To look at Keogh, and to hear of her love for running, one might think she runs 100 miles a week. That's not so. She doesn't even know how far she goes when she runs through the streets of McLean for an hour a day. "It could be eight miles, I guess," she said. Dowd said she runs 65 to 70 miles a week when she's in heavy training; 55 to 60 a week is usual. This leaves time for a life outside running, for things like friends (most of whom are runners, too) and movies and extracurricular high school activities.

She has a 3.95 grade point average, which means she got a B once, and she plans to study sports medicine at Texas. She definitely does not live life on a whim. Each day, she does her homework at the same time, eats meals at the same time and goes to sleep at the same time.

"Jumbo Elliott, the old Villanova coach, once said, 'Live your life like a clock.' She doesn't know who Jumbo Elliott was, but she does it," Dowd said.

Lately, Keogh has been complaining about her right foot. It has been sore since early April, when she jammed a toe inside tight running shoes. Dowd, playing the role of sarcastic coach as well as sympathetic best friend, teases Keogh about her problem, but understands.

"When you're a runner and your foot is not right, it's the equivalent of being Beethoven and having someone slam your hand in the door," Dowd said. It has slowed her down some, leading to her disappointing fourth-place finish in the 1,600 in the regional meet in mid-May and her loss to Lake Braddock's Wendy Neely in the state 1,600 the next week.

"It's really hard to go into a race totally confident when your foot hurts," she said.

But whether it's confidence or pure, sinewy talent she runs on, no one knows. There is no doubt, however, that she just wears her competition down. If Keogh were to run a short race, say 400 meters, against top high-school runners, she would lose.

"The big joke is Erin is a national record-holder in four events, but she can't run anything under a mile," said Dowd. "She's so slow when you consider how fast she is."

Her 400-meter time is usually 64 to 66 seconds. She is able to run the 1,600 in 70- or 71-second quarters. That's consistency and speed for the long term, not the short.

"I don't have the muscle to have leg speed," Keogh said. "I have no pickup."

But over the long haul, she is merciless.

"The two words I always use to describe Erin are 'relentless' and 'consistent,' " Dowd said. "What two better words are there for a distance runner?"