KENYANS NOT BORN TO RUN MARATHONS.

Byline: KAREN CROUSE

Once you find your rhythm, you can't feel the pain. That's one of marathon running's enduring myths, along with this: marathon runners aren't made, they're born, preferably in Kenya.

Hellen Kimaiyo is one of 13 Kenyans with world-class credentials who will compete in the L.A. Marathon. Sunday's 26.2-mile race will mark the first time she will compete at the distance directly against countrywoman Lorna Ziplagat, the reigning women's champion.

Someone asked Kimaiyo the other day if it's true what people say, that Kenyans start running long distances shortly after they learn to walk. Her eyes narrowed and confusion swept over her face as if she had misunderstood the question. Her look was not unlike that of an Angeleno when asked if it's true that every house in Southern California has direct access to the beach.

``Oh no,'' she said in lilting English, allowing herself a delicate laugh. ``That's the wrong idea. I started when I was 16. That's about right, I think. You cannot get a child running below 10.''

Kimaiyo should know; she has 12-year-old daughter Gladys and 8-year-old son Timothy with husband Charles, who doubles as her trainer.

``My daughter is interested, I think,'' said Kimaiyo, who has a personal best in the marathon of 2 hours, 29.45. ``Sometimes she says, `Mom, when I grow up, I want to run like you.' '' Kimaiyo smiled. ``But another day she says she'd like to do this and that. We'll see.''

The fickleness of youth, it seems, needs no translation. It is the same in any culture.

``The only thing I can say maybe is the difference between Americans and Kenyans is that we walk to school, two to five kilometers, maybe, each way,'' Kimaiyo offered helpfully.

That could change in Kimaiyo's family, depending on how she fares here. The first-place finisher in the men's and women's races will receive a $24,000 Honda sedan in addition to a $30,000 check.

There are only a handful of runners who have a realistic shot at Sunday's riches. But the L.A. Marathon has something for every one of its 20,000 expected entrants. For Angeleno Jerry Robinson, running is its own reward.

``I run because I need it for my sanity,'' said Robinson, who has completed all 12 L.A. Marathons that have been contested. ``I can't imagine life without it.''

If not for running, he might not be alive at all.

Like Kimaiyo, Robinson came to marathon running late. Unlike Kimaiyo, he wasn't a world-caliber runner in another distance first. Kimaiyo was 16 when she competed in the 3,000 meters at the 1984 Summer Olympics in L.A.

For the first 29 years of his life, Robinson's best event was The Expense Account Lunch. He kept track of his progress, if you will, by the belt notches he loosened with regularity.

When his pants no longer fit, Robinson reluctantly joined a gym. The first time he stepped on a treadmill, he lasted two minutes.

In 1978 he moved from the treadmill to the track and, eventually, to the road, beach, sidewalk, field - as far and wide as his feet could carry him. In 1986 he ran his first of 24 marathons, in L.A., despite never having completed a training run of more than 10 miles.

He finished in just under four hours and was so dehydrated he required medical attention. ``After feeling that way, I swore off marathons,'' Robinson said.

He un-retired his running shoes a few days later, he said, ``when I got the craving again.''

All this time Robinson's heart should have been thanking him, but instead it was slowly betraying him. He found out in 1977 that his aortic valve had calcified and was leaking blood back into his heart. Doctors told him the valve eventually would have to be replaced. In August of 1996, shortly after his heart rate skyrocketed during a routine eight-mile training run, Robinson underwent the surgery.

When doctors looked at his heart they saw no trace of all the prime rib lunches that once had been Robinson's staple. ``They said that all my arteries were clean and that all the marathoning had paid off big-time,'' Robinson said.

Seven months after the surgery he completed his 12th L.A. Marathon wearing a heart-rate monitor that remains as much a part of his race day get-up as a singlet.

``My friends think it's amazing,'' Robinson said of his journey.

Heck, he said with a laugh, ``I think it's amazing.''

Sunday, Robinson's and Kimaiyo's worlds will collide.

``You know, it's nice to look around and see so many people running,'' Kimaiyo said. ``You don't have to only run when you are winning money. When you are running, it is nice because it just feels like you're doing it for your own good.''

Which leads us to one of the fundamental truths about marathon running: it feels so good once it stops hurting.