The balance beam competition went down to the last participant in the two-day Capital Cup women's gymnastics meet yesterday at Montgomery-Rockville College before Heidi Brady of the Acronauts (Bloomfield, Mich.) won with a 9.5 score for an 18.75 total.

Jenny Rhee, of the Prince George's Gymnastics Club of Beltsville was second (18.65) and Sheena Loo of MarVaTeens of Rockville came in third (18:45).

Loo, the MarVaTeens' only finalist in any of the four events, got a 9.35 score before Rhee earned a 9.4 with fluid execution of movements, including consecutive one-handed back somersaults.

All-around champion Kim Hamilton (Richmond Olympiad) took first in the floor exercise and uneven bars.

MarVaTeens Coach Gary Anderson was pleased with Loo, a student at E. Brooke Lee Intermediate School in Wheaton.

"She was just fantastic," Anderson said. "She was up there going against three girls who had been in international competition. This was her first big meet and she moved from ninth to third in the finals. That was more than any coach could ask for."

."The pressure was really on her," said Elizabeth Loo, Sheena's mother. "But beam is her most consistent and it's one she loves the most."

Rhee, who was sixth all-around with a 36.05 total, also competed on the uneven bars but failed to regrasp the bar after a circling somersault. Her teammate, Karen Nelson, was sixth in the floor exercise (18.45).

Marie Robbins of the Karons (Fairfax) was the vaulting silver medalist. She added a 9.5 to her 9.55 from Saturday for a 19.05. Joyce Wilborn (North Stars of New Jersey), the meet's most consistent performer, won vaulting (19.35).

Betsy Erickson of Docksiders (Annapolis) reached the final in three events (floor, bars and vaulting).

She tied for fourth in vaulting (18.85) and fifth in floor (18.45).

The meet involved 48 teams and 150 gymnasts from the East and Midwest.