With a sudden burst of her flailing elbows and pumping legs. Mary Shea of Raleigh. N.C., flew past defending champion Aileen O'Conner with two kilometers to go to win the Road Runners Club of America's Capital Area Women's 10-Kilometer Championship Run yesterday at East Potomac Park.

Shea's time was 34:59 in leading the field of 326 finishers.

For the first eight kilimeters, spectators peered over the sand traps of the Hains Point golf course to see She and O'Conner running stride for stride. Shea suddenly shot to the front and won by seven seconds.

Shea said she got off to a slow start. "When I heard that I did the first mile in 5:38, I just couldn't believe it," said Shea.

O'Conner said, "Mary shot out like a cannon when she heard the mile time."

Part of the slow start could be attributed to the sudden start of the race which caught several runners tying their shoe laces, taking drinks and loosening up.

At the midway point of the race, Shea and O'Conner were dead even at 17:35.

The spectators watching from a distance could see Shea take the lead because of Shea's distinctive running style in which her elbows are extended from her body.

Shea said her style "is natural - my whole family runs like that. I don't even think about it anymore."

During the race. Shea said she just kept thinking. "Keep running, there's not that far to go. And I also spent some time listening for footsteps behind me."

Besides O'Conner, those distant footsteps belonged to Jill Hayworth, who, like O'Conner is from Washington's Catholic Youth Organization. Hayworth ran third in 37:53.

Fourth was Georgetown University student Chris Shea (no relation to Mary), who ran a 38:08. Shea has been running long distance races for less than a year.

Ruth Drengwitz ran fifth in 38:08.

In the age-group competition. Mary Shea won the 19-and-under. Kathy Heckman won the 20. 29-year-old, Mary Ellen Williams, who placed sixth overall, won the 30-39-year-old, and Rachel Bourn, 49, captured the over-4- award. Bourne placed 97st overall.

Another highly impressive finisher was jenifer Amy, & who said she has been racing since she was 4 1/2.She finished 37th.

In the team competition, DC-CYO, led by O'Conner and Hayworth, placed first with a total of 53 points. Second was the Washington Running Club at 60 and the Washington run-hers were third at 105.