A year ago. after three months of race-walking experience, Chris Shea fell down in the stretch trying desperately to finish fourth and win a T-shirt in the National AAU Track and Field Championships. Today, she smashed the world record.

The 18-year-old Georgetown freshman covered a mile heel-and-toe style in 6 minutes 58.9 seconds, becoming the first woman to walk a mile indoors under 7 minutes.

As the sparse crowd at the afternoon portion of the 92nd annual AAU meet waited for former record-holder Susan Brodock to collect her sixth straight title, Shea moved ahead of Brodock with a half mile to go and increased her lead to the finish.

"My goal was just not to fall this year," Shea said. "I had my left ankle taped, because last year I had no idea of the strain walking puts on the ankle. I was trying to finish fourth, because the top four get T-shirts, and when a girl started to pass me near the finish I gave it a little extra and the ankle collapsed and I fell."

While others were being disqualified for running, Shea was satisfying the judges with excellent form. That in itself was a remarkable feat, because Shea, the U.S. junior recordholder in the mile walk outdoors, is noted at Georgetown for her running prowess. Next week, she will be running the 1,000 in the Missouri Women's Invitational.

This was only the third race walk of the indoor season for Shea, since competition is hard to find. She walked against men in the Philadelphia Track Classic, then posted a qualifying time in an open meet at Lewisburg, Pa.

"I went out way too fast in the Philly meet because of the pace the men set and I felt terrible," Shea said. "But it was a thrill to be in the same race with Todd Scully."

This week, Shea trained underneath the K Street Expressway, about the only place in Washington that was free of snow. She had no thoughts of a world record, but "I just wanted to try to see if I could beat Sue. I hoped I could."

Shea spent seven years as an AAU swimmer before she was converted to track by Bruce MacDonald, her high school coach in Port Washington, N.Y., and a noted walker.

"She missed a swim practice one day and I saw her running, instead," MacDonald said. "She could go as fast as my best two-miler and she didn't know how to stride properly. She made the switch easily and she's good because of her determination and because of the strength she got from seven years of swimming. Track is easier, because you can fit in so many variations in the type of training."

"I was sick of swimming, so I just went running one day and he saw me," Shea said. "I like running because I can see what I'm doing. I like running better than walking, but I guess I'm more successful walking. I'd like to break five minutes running the mile this year."

Shea's mother, Sue, watched the race today.

"I was overjoyed when she got out of it (swimming)," Mrs. Shea said. "I had enough of sitting by a pool. The steam was starting to get to my head."

There was only one regret for the new world record-holder.

"I was embarrassed the way my backside stuck out in my shorts," Shea said. "I've got to lose some weight."